Add hologram item

core/src/main/java/de/epiceric/shopchest/shop/hologram/Hologram.java

@@ -2,86 +2,87 @@ package de.epiceric.shopchest.shop.hologram;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 import org.bukkit.Location;
 import org.bukkit.OfflinePlayer;
 import org.bukkit.entity.Player;
+import org.bukkit.util.Vector;
 
 import de.epiceric.shopchest.api.ShopChest;
 import de.epiceric.shopchest.api.shop.Shop;
 import de.epiceric.shopchest.shop.ShopImpl;
-import de.epiceric.shopchest.util.NmsUtil;
 
 public class Hologram {
-
-    /**
-     * Constructs a new hologram line
-     * 
-     * @param location the line's location
-     * @param text the line's text
-     * @return the hologram line
-     */
-    public static IHologramLine newHologramLine(Location location, String text) {
-        switch (NmsUtil.getServerVersion()) {
-            case "v1_8_R1": return new de.epiceric.shopchest.shop.hologram.v1_8_R1.HologramLine(location, text);
-            case "v1_8_R2": return new de.epiceric.shopchest.shop.hologram.v1_8_R2.HologramLine(location, text);
-            case "v1_8_R3": return new de.epiceric.shopchest.shop.hologram.v1_8_R3.HologramLine(location, text);
-            case "v1_9_R1": return new de.epiceric.shopchest.shop.hologram.v1_9_R1.HologramLine(location, text);
-            case "v1_9_R2": return new de.epiceric.shopchest.shop.hologram.v1_9_R2.HologramLine(location, text);
-            case "v1_10_R1": return new de.epiceric.shopchest.shop.hologram.v1_10_R1.HologramLine(location, text);
-            case "v1_11_R1": return new de.epiceric.shopchest.shop.hologram.v1_11_R1.HologramLine(location, text);
-            case "v1_12_R1": return new de.epiceric.shopchest.shop.hologram.v1_12_R1.HologramLine(location, text);
-            case "v1_13_R1": return new de.epiceric.shopchest.shop.hologram.v1_13_R1.HologramLine(location, text);
-            case "v1_13_R2": return new de.epiceric.shopchest.shop.hologram.v1_13_R2.HologramLine(location, text);
-            case "v1_14_R1": return new de.epiceric.shopchest.shop.hologram.v1_14_R1.HologramLine(location, text);
-            case "v1_15_R1": return new de.epiceric.shopchest.shop.hologram.v1_15_R1.HologramLine(location, text);
-            default: throw new IllegalStateException("Invalid server version: " + NmsUtil.getServerVersion());
-        }
-    }
-
     private final Shop shop;
-    private List<IHologramLine> lines = new ArrayList<>();
+    private final List<IHologramLine> lines = new ArrayList<>();
+    private final IHologramItem item;
 
     public Hologram(ShopChest plugin, Shop shop) {
         this.shop = shop;
+        this.item = HologramFactory.newHologramItem(getItemLocation(), shop.getProduct().getItemStack());
 
         int topLine = shop.canPlayerBuy() && shop.canPlayerSell() ? 3 : 2;
 
         // TODO: Configurable
-        lines.add(newHologramLine(getLocation(topLine), shop.getVendor().map(OfflinePlayer::getName).orElse("§cAdmin Shop")));
+
-        lines.add(newHologramLine(getLocation(topLine - 1), shop.getProduct().getAmount() + " §7x §f" + shop.getProduct().getLocalizedName()));
+        lines.add(HologramFactory.newHologramLine(getLineLocation(topLine),
-        if (shop.canPlayerBuy()) lines.add(newHologramLine(getLocation(topLine - 2), "§eBuy for " + plugin.formatEconomy(shop.getBuyPrice())));
+            shop.getVendor().map(OfflinePlayer::getName).orElse("§cAdmin Shop")));
-        if (shop.canPlayerSell()) lines.add(newHologramLine(getLocation(0), "§eSell for " + plugin.formatEconomy(shop.getSellPrice())));
+
+        lines.add(HologramFactory.newHologramLine(getLineLocation(topLine - 1),
+                shop.getProduct().getAmount() + " §7x §f" + shop.getProduct().getLocalizedName()));
+
+        if (shop.canPlayerBuy()) lines.add(HologramFactory.newHologramLine(getLineLocation(topLine - 2),
+                "§eBuy for " + plugin.formatEconomy(shop.getBuyPrice())));
+
+        if (shop.canPlayerSell()) lines.add(HologramFactory.newHologramLine(getLineLocation(0),
+                "§eSell for " + plugin.formatEconomy(shop.getSellPrice())));
     }
 
-    private Location getLocation(int lineFromBottom) {
+    private Location getCenterOfChest() {
-        double lineHeight = 0.25;
+        ShopImpl shop = (ShopImpl) this.shop;
-        Location loc = shop.getLocation().subtract(0, 0.75, 0);
+        Location location = shop.getLocation();
-        Location otherLoc = ((ShopImpl) shop).getOtherLocation().orElse(null);
+        Optional<Location> optional = shop.getOtherLocation();
 
-        if (otherLoc == null) {
+        if (optional.isPresent()) {
-            return loc.add(0.5, lineFromBottom * lineHeight, 0.5);
+            Location otherLoc = optional.get();
-        }
+            Vector diff = otherLoc.subtract(location).toVector();
-        
+
-        if (loc.getX() == otherLoc.getX()) {
+            // Invert cross vector direction if diff has negative x or z
-            double zDiff = otherLoc.subtract(loc).getZ();
+            Vector cross = (diff.getX() < 0.1 || diff.getZ() < 0.1)
-            return loc.add(0.5, lineFromBottom * lineHeight, zDiff);
+                ? diff.getCrossProduct(new Vector(0, -0.5, 0))
+                : diff.getCrossProduct(new Vector(0, 0.5, 0));
+
+            location.add(diff.add(cross));
         } else {
-            double xDiff = otherLoc.subtract(loc).getX();
+            location.add(0.5, 0, 0.5);
-            return loc.add(xDiff, lineFromBottom * lineHeight, 0.5);
         }
+
+        return location;
+    }
+
+    private Location getItemLocation() {
+        double itemLift = 0.9;
+        return getCenterOfChest().add(0, itemLift, 0);
+    }
+
+    private Location getLineLocation(int lineFromBottom) {
+        double lineHeight = 0.25;
+        double armorStandLift = -0.75;
+        return getCenterOfChest().add(0, lineFromBottom * lineHeight - armorStandLift, 0);
     }
 
     /**
      * Hides the hologram from all players in the hologram's world and removes all lines
      */
     public void destroy() {
+        item.destroy();
         lines.forEach(IHologramLine::destroy);
         lines.clear();
     }
 
     /**
-     * Displays the hologram to the given player
+     * Displays the hologram text to the given player
      * 
      * @param player the player to show the hologram to
      */
@@ -90,7 +91,7 @@ public class Hologram {
     }
 
     /**
-     * Hides the hologram from the given player
+     * Hides the hologram text from the given player
      * 
      * @param player the player to hide the hologram from
      */

core/src/main/java/de/epiceric/shopchest/shop/hologram/HologramFactory.java

@@ -0,0 +1,47 @@
+package de.epiceric.shopchest.shop.hologram;
+
+import org.bukkit.Location;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.util.NmsUtil;
+
+class HologramFactory {
+    private HologramFactory() {
+    }
+
+    static IHologramLine newHologramLine(Location location, String text) {
+        switch (NmsUtil.getServerVersion()) {
+            case "v1_8_R1": return new de.epiceric.shopchest.shop.hologram.v1_8_R1.HologramLine(location, text);
+            case "v1_8_R2": return new de.epiceric.shopchest.shop.hologram.v1_8_R2.HologramLine(location, text);
+            case "v1_8_R3": return new de.epiceric.shopchest.shop.hologram.v1_8_R3.HologramLine(location, text);
+            case "v1_9_R1": return new de.epiceric.shopchest.shop.hologram.v1_9_R1.HologramLine(location, text);
+            case "v1_9_R2": return new de.epiceric.shopchest.shop.hologram.v1_9_R2.HologramLine(location, text);
+            case "v1_10_R1": return new de.epiceric.shopchest.shop.hologram.v1_10_R1.HologramLine(location, text);
+            case "v1_11_R1": return new de.epiceric.shopchest.shop.hologram.v1_11_R1.HologramLine(location, text);
+            case "v1_12_R1": return new de.epiceric.shopchest.shop.hologram.v1_12_R1.HologramLine(location, text);
+            case "v1_13_R1": return new de.epiceric.shopchest.shop.hologram.v1_13_R1.HologramLine(location, text);
+            case "v1_13_R2": return new de.epiceric.shopchest.shop.hologram.v1_13_R2.HologramLine(location, text);
+            case "v1_14_R1": return new de.epiceric.shopchest.shop.hologram.v1_14_R1.HologramLine(location, text);
+            case "v1_15_R1": return new de.epiceric.shopchest.shop.hologram.v1_15_R1.HologramLine(location, text);
+            default: throw new IllegalStateException("Invalid server version: " + NmsUtil.getServerVersion());
+        }
+    }
+    
+    static IHologramItem newHologramItem(Location location, ItemStack itemStack) {
+        switch (NmsUtil.getServerVersion()) {
+            case "v1_8_R1": return new de.epiceric.shopchest.shop.hologram.v1_8_R1.HologramItem(location, itemStack);
+            case "v1_8_R2": return new de.epiceric.shopchest.shop.hologram.v1_8_R2.HologramItem(location, itemStack);
+            case "v1_8_R3": return new de.epiceric.shopchest.shop.hologram.v1_8_R3.HologramItem(location, itemStack);
+            case "v1_9_R1": return new de.epiceric.shopchest.shop.hologram.v1_9_R1.HologramItem(location, itemStack);
+            case "v1_9_R2": return new de.epiceric.shopchest.shop.hologram.v1_9_R2.HologramItem(location, itemStack);
+            case "v1_10_R1": return new de.epiceric.shopchest.shop.hologram.v1_10_R1.HologramItem(location, itemStack);
+            case "v1_11_R1": return new de.epiceric.shopchest.shop.hologram.v1_11_R1.HologramItem(location, itemStack);
+            case "v1_12_R1": return new de.epiceric.shopchest.shop.hologram.v1_12_R1.HologramItem(location, itemStack);
+            case "v1_13_R1": return new de.epiceric.shopchest.shop.hologram.v1_13_R1.HologramItem(location, itemStack);
+            case "v1_13_R2": return new de.epiceric.shopchest.shop.hologram.v1_13_R2.HologramItem(location, itemStack);
+            case "v1_14_R1": return new de.epiceric.shopchest.shop.hologram.v1_14_R1.HologramItem(location, itemStack);
+            case "v1_15_R1": return new de.epiceric.shopchest.shop.hologram.v1_15_R1.HologramItem(location, itemStack);
+            default: throw new IllegalStateException("Invalid server version: " + NmsUtil.getServerVersion());
+        }
+    }
+}

nms/interfaces/src/main/java/de/epiceric/shopchest/shop/hologram/IHologramItem.java

@@ -0,0 +1,61 @@
+package de.epiceric.shopchest.shop.hologram;
+
+import org.bukkit.Location;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+public interface IHologramItem {
+    
+    /**
+     * Sets the location of this item and sends the update to
+     * all players in the hologram's world
+     * 
+     * @param location the location to set
+     */
+    void setLocation(Location location);
+
+    /**
+     * Gets the current location
+     * 
+     * @return the location
+     */
+    Location getLocation();
+
+    /**
+     * Sets the item shown in the hologram
+     * <p>
+     * The amount of the item stack will always be set to 1.
+     * 
+     * @param itemStack the item to set
+     */
+    void setItemStack(ItemStack itemStack);
+
+    /**
+     * Gets the current item of the hologram
+     * 
+     * @return the item
+     */
+    ItemStack getItemStack();
+
+    /**
+     * Displays the item to the given player
+     * 
+     * @param player the player to show the item to
+     */
+    void showPlayer(Player player);
+
+    /**
+     * Hides the item from the given player
+     * 
+     * @param player the player to hide the item from
+     */
+    void hidePlayer(Player player);
+
+    /**
+     * Hides the item from all players in the hologram's world
+     */
+    default void destroy() {
+        getLocation().getWorld().getPlayers().forEach(this::hidePlayer);
+    }
+    
+}

nms/v10r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_10_R1/HologramItem.java

@@ -0,0 +1,130 @@
+package de.epiceric.shopchest.shop.hologram.v1_10_R1;
+
+import java.lang.reflect.AccessibleObject;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import com.google.common.base.Optional;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_10_R1.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_10_R1.DataWatcher;
+import net.minecraft.server.v1_10_R1.DataWatcherObject;
+import net.minecraft.server.v1_10_R1.Entity;
+import net.minecraft.server.v1_10_R1.EntityItem;
+import net.minecraft.server.v1_10_R1.Packet;
+import net.minecraft.server.v1_10_R1.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_10_R1.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_10_R1.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_10_R1.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private DataWatcherObject<Optional<net.minecraft.server.v1_10_R1.ItemStack>> item;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        Packet<?> teleportPacket = HologramUtil.createTeleportPacket(id, location, false);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.register(item, Optional.of(getNmsItemStack())); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    @SuppressWarnings("unchecked")
+    private DataWatcher createDataWatcher() {
+        try {
+            Field fAirTicks = Entity.class.getDeclaredField("az");
+            Field fNoGravity = Entity.class.getDeclaredField("aD");
+            Field fItem = EntityItem.class.getDeclaredField("c");
+
+            setAccessible(fAirTicks, fNoGravity, fItem);
+
+            item = (DataWatcherObject<Optional<net.minecraft.server.v1_10_R1.ItemStack>>) fItem.get(null);
+            DataWatcherObject<Integer> airTicks = (DataWatcherObject<Integer>) fAirTicks.get(null);
+            DataWatcherObject<Boolean> noGravity = (DataWatcherObject<Boolean>) fNoGravity.get(null);
+
+            DataWatcher dataWatcher = new DataWatcher(null);
+            dataWatcher.register(airTicks, 300);
+            dataWatcher.register(noGravity, true);
+            dataWatcher.register(item, Optional.of(getNmsItemStack()));
+
+            return dataWatcher;
+        } catch (ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    private net.minecraft.server.v1_10_R1.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+
+    private void setAccessible(AccessibleObject... args) {
+        Arrays.stream(args).forEach(arg -> arg.setAccessible(true));
+    }
+}

nms/v10r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_10_R1/HologramLine.java

@@ -1,30 +1,24 @@
 package de.epiceric.shopchest.shop.hologram.v1_10_R1;
 
-import java.io.IOException;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Optional;
-import java.util.UUID;
 
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_10_R1.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_10_R1.DataWatcher;
 import net.minecraft.server.v1_10_R1.DataWatcherObject;
 import net.minecraft.server.v1_10_R1.Entity;
 import net.minecraft.server.v1_10_R1.EntityArmorStand;
 import net.minecraft.server.v1_10_R1.IChatBaseComponent;
 import net.minecraft.server.v1_10_R1.Packet;
-import net.minecraft.server.v1_10_R1.PacketDataSerializer;
 import net.minecraft.server.v1_10_R1.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_10_R1.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_10_R1.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_10_R1.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_10_R1.PlayerConnection;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -45,16 +39,16 @@ public class HologramLine implements IHologramLine {
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
-        PacketPlayOutEntityTeleport packet = createTeleportPacket();
+        PacketPlayOutEntityTeleport packet = HologramUtil.createTeleportPacket(id, location, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, packet));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, packet));
     }
 
     @Override
@@ -70,7 +64,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.register(customName, text);
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -84,7 +78,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -93,59 +87,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private PacketPlayOutEntityTeleport createTeleportPacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // yaw
-        s.writeByte(0); // pitch
-        s.writeBoolean(true); // on ground
-
-        try {
-            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
-            packet.a(s);
-            return packet;
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
-
-        return null;
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.a(UUID.randomUUID()); // uuid
-        s.writeByte(78); // type
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // ?
-        s.writeShort(0); // mot x
-        s.writeShort(0); // mot y
-        s.writeShort(0); // mot z
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     @SuppressWarnings("unchecked")

nms/v10r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_10_R1/HologramUtil.java

@@ -0,0 +1,114 @@
+package de.epiceric.shopchest.shop.hologram.v1_10_R1;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.UUID;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_10_R1.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_10_R1.Entity;
+import net.minecraft.server.v1_10_R1.Packet;
+import net.minecraft.server.v1_10_R1.PacketDataSerializer;
+import net.minecraft.server.v1_10_R1.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_10_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_10_R1.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id + 1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType == 78 ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.a(UUID.randomUUID()); // uuid
+        serializer.writeByte(entityType); // entity type
+        serializer.writeDouble(location.getX()); // x
+        serializer.writeDouble(location.getY() + yLift); // y
+        serializer.writeDouble(location.getZ()); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+
+    /**
+     * Creates a PacketPlayOutEntityTeleport
+     * 
+     * @param id the entity ID
+     * @param location the new entity location
+     * @param lift whether the entity will be lifted by 1.975
+     * @return the packet
+     */
+    public static PacketPlayOutEntityTeleport createTeleportPacket(int id, Location location, boolean lift) {
+        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
+        s.d(id); // id
+        s.writeDouble(location.getX()); // x
+        s.writeDouble(location.getY() + (lift ? 1.975 : 0)); // y
+        s.writeDouble(location.getZ()); // z
+        s.writeByte(0); // yaw
+        s.writeByte(0); // pitch
+        s.writeBoolean(true); // on ground
+
+        try {
+            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
+            packet.a(s);
+            return packet;
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            s.release();
+        }
+
+        return null;
+    }
+}

nms/v11r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_11_R1/HologramItem.java

@@ -0,0 +1,128 @@
+package de.epiceric.shopchest.shop.hologram.v1_11_R1;
+
+import java.lang.reflect.AccessibleObject;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_11_R1.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_11_R1.DataWatcher;
+import net.minecraft.server.v1_11_R1.DataWatcherObject;
+import net.minecraft.server.v1_11_R1.Entity;
+import net.minecraft.server.v1_11_R1.EntityItem;
+import net.minecraft.server.v1_11_R1.Packet;
+import net.minecraft.server.v1_11_R1.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_11_R1.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_11_R1.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_11_R1.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private DataWatcherObject<net.minecraft.server.v1_11_R1.ItemStack> item;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        Packet<?> teleportPacket = HologramUtil.createTeleportPacket(id, location, false);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.register(item, getNmsItemStack()); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    @SuppressWarnings("unchecked")
+    private DataWatcher createDataWatcher() {
+        try {
+            Field fAirTicks = Entity.class.getDeclaredField("az");
+            Field fNoGravity = Entity.class.getDeclaredField("aD");
+            Field fItem = EntityItem.class.getDeclaredField("c");
+
+            setAccessible(fAirTicks, fNoGravity, fItem);
+
+            item = (DataWatcherObject<net.minecraft.server.v1_11_R1.ItemStack>) fItem.get(null);
+            DataWatcherObject<Integer> airTicks = (DataWatcherObject<Integer>) fAirTicks.get(null);
+            DataWatcherObject<Boolean> noGravity = (DataWatcherObject<Boolean>) fNoGravity.get(null);
+
+            DataWatcher dataWatcher = new DataWatcher(null);
+            dataWatcher.register(airTicks, 300);
+            dataWatcher.register(noGravity, true);
+            dataWatcher.register(item, getNmsItemStack());
+
+            return dataWatcher;
+        } catch (ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    private net.minecraft.server.v1_11_R1.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+
+    private void setAccessible(AccessibleObject... args) {
+        Arrays.stream(args).forEach(arg -> arg.setAccessible(true));
+    }
+}

nms/v11r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_11_R1/HologramLine.java

@@ -1,30 +1,24 @@
 package de.epiceric.shopchest.shop.hologram.v1_11_R1;
 
-import java.io.IOException;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Optional;
-import java.util.UUID;
 
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_11_R1.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_11_R1.DataWatcher;
 import net.minecraft.server.v1_11_R1.DataWatcherObject;
 import net.minecraft.server.v1_11_R1.Entity;
 import net.minecraft.server.v1_11_R1.EntityArmorStand;
 import net.minecraft.server.v1_11_R1.IChatBaseComponent;
 import net.minecraft.server.v1_11_R1.Packet;
-import net.minecraft.server.v1_11_R1.PacketDataSerializer;
 import net.minecraft.server.v1_11_R1.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_11_R1.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_11_R1.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_11_R1.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_11_R1.PlayerConnection;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -45,16 +39,16 @@ public class HologramLine implements IHologramLine {
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
-        PacketPlayOutEntityTeleport packet = createTeleportPacket();
+        PacketPlayOutEntityTeleport packet = HologramUtil.createTeleportPacket(id, location, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, packet));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, packet));
     }
 
     @Override
@@ -70,7 +64,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.register(customName, text);
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -84,7 +78,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -93,59 +87,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private PacketPlayOutEntityTeleport createTeleportPacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // yaw
-        s.writeByte(0); // pitch
-        s.writeBoolean(true); // on ground
-
-        try {
-            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
-            packet.a(s);
-            return packet;
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
-
-        return null;
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.a(UUID.randomUUID()); // uuid
-        s.writeByte(78); // type
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // ?
-        s.writeShort(0); // mot x
-        s.writeShort(0); // mot y
-        s.writeShort(0); // mot z
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     @SuppressWarnings("unchecked")

nms/v11r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_11_R1/HologramUtil.java

@@ -0,0 +1,114 @@
+package de.epiceric.shopchest.shop.hologram.v1_11_R1;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.UUID;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_11_R1.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_11_R1.Entity;
+import net.minecraft.server.v1_11_R1.Packet;
+import net.minecraft.server.v1_11_R1.PacketDataSerializer;
+import net.minecraft.server.v1_11_R1.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_11_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_11_R1.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id + 1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType == 78 ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.a(UUID.randomUUID()); // uuid
+        serializer.writeByte(entityType); // entity type
+        serializer.writeDouble(location.getX()); // x
+        serializer.writeDouble(location.getY() + yLift); // y
+        serializer.writeDouble(location.getZ()); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+
+    /**
+     * Creates a PacketPlayOutEntityTeleport
+     * 
+     * @param id the entity ID
+     * @param location the new entity location
+     * @param lift whether the entity will be lifted by 1.975
+     * @return the packet
+     */
+    public static PacketPlayOutEntityTeleport createTeleportPacket(int id, Location location, boolean lift) {
+        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
+        s.d(id); // id
+        s.writeDouble(location.getX()); // x
+        s.writeDouble(location.getY() + (lift ? 1.975 : 0)); // y
+        s.writeDouble(location.getZ()); // z
+        s.writeByte(0); // yaw
+        s.writeByte(0); // pitch
+        s.writeBoolean(true); // on ground
+
+        try {
+            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
+            packet.a(s);
+            return packet;
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            s.release();
+        }
+
+        return null;
+    }
+}

nms/v12r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_12_R1/HologramItem.java

@@ -0,0 +1,128 @@
+package de.epiceric.shopchest.shop.hologram.v1_12_R1;
+
+import java.lang.reflect.AccessibleObject;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_12_R1.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_12_R1.DataWatcher;
+import net.minecraft.server.v1_12_R1.DataWatcherObject;
+import net.minecraft.server.v1_12_R1.Entity;
+import net.minecraft.server.v1_12_R1.EntityItem;
+import net.minecraft.server.v1_12_R1.Packet;
+import net.minecraft.server.v1_12_R1.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_12_R1.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_12_R1.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_12_R1.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private DataWatcherObject<net.minecraft.server.v1_12_R1.ItemStack> item;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        Packet<?> teleportPacket = HologramUtil.createTeleportPacket(id, location, false);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.register(item, getNmsItemStack()); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    @SuppressWarnings("unchecked")
+    private DataWatcher createDataWatcher() {
+        try {
+            Field fAirTicks = Entity.class.getDeclaredField("aA");
+            Field fNoGravity = Entity.class.getDeclaredField("aE");
+            Field fItem = EntityItem.class.getDeclaredField("c");
+
+            setAccessible(fAirTicks, fNoGravity, fItem);
+
+            item = (DataWatcherObject<net.minecraft.server.v1_12_R1.ItemStack>) fItem.get(null);
+            DataWatcherObject<Integer> airTicks = (DataWatcherObject<Integer>) fAirTicks.get(null);
+            DataWatcherObject<Boolean> noGravity = (DataWatcherObject<Boolean>) fNoGravity.get(null);
+
+            DataWatcher dataWatcher = new DataWatcher(null);
+            dataWatcher.register(airTicks, 300);
+            dataWatcher.register(noGravity, true);
+            dataWatcher.register(item, getNmsItemStack());
+
+            return dataWatcher;
+        } catch (ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    private net.minecraft.server.v1_12_R1.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+
+    private void setAccessible(AccessibleObject... args) {
+        Arrays.stream(args).forEach(arg -> arg.setAccessible(true));
+    }
+}

nms/v12r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_12_R1/HologramLine.java

@@ -1,30 +1,24 @@
 package de.epiceric.shopchest.shop.hologram.v1_12_R1;
 
-import java.io.IOException;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Optional;
-import java.util.UUID;
 
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_12_R1.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_12_R1.DataWatcher;
 import net.minecraft.server.v1_12_R1.DataWatcherObject;
 import net.minecraft.server.v1_12_R1.Entity;
 import net.minecraft.server.v1_12_R1.EntityArmorStand;
 import net.minecraft.server.v1_12_R1.IChatBaseComponent;
 import net.minecraft.server.v1_12_R1.Packet;
-import net.minecraft.server.v1_12_R1.PacketDataSerializer;
 import net.minecraft.server.v1_12_R1.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_12_R1.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_12_R1.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_12_R1.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_12_R1.PlayerConnection;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -45,16 +39,16 @@ public class HologramLine implements IHologramLine {
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
-        PacketPlayOutEntityTeleport packet = createTeleportPacket();
+        PacketPlayOutEntityTeleport packet = HologramUtil.createTeleportPacket(id, location, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, packet));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, packet));
     }
 
     @Override
@@ -70,7 +64,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.register(customName, text);
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -84,7 +78,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -93,59 +87,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private PacketPlayOutEntityTeleport createTeleportPacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // yaw
-        s.writeByte(0); // pitch
-        s.writeBoolean(true); // on ground
-
-        try {
-            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
-            packet.a(s);
-            return packet;
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
-
-        return null;
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.a(UUID.randomUUID()); // uuid
-        s.writeByte(78); // type
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // ?
-        s.writeShort(0); // mot x
-        s.writeShort(0); // mot y
-        s.writeShort(0); // mot z
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     @SuppressWarnings("unchecked")

nms/v12r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_12_R1/HologramUtil.java

@@ -0,0 +1,114 @@
+package de.epiceric.shopchest.shop.hologram.v1_12_R1;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.UUID;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_12_R1.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_12_R1.Entity;
+import net.minecraft.server.v1_12_R1.Packet;
+import net.minecraft.server.v1_12_R1.PacketDataSerializer;
+import net.minecraft.server.v1_12_R1.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_12_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_12_R1.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id + 1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType == 78 ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.a(UUID.randomUUID()); // uuid
+        serializer.writeByte(entityType); // entity type
+        serializer.writeDouble(location.getX()); // x
+        serializer.writeDouble(location.getY() + yLift); // y
+        serializer.writeDouble(location.getZ()); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+
+    /**
+     * Creates a PacketPlayOutEntityTeleport
+     * 
+     * @param id the entity ID
+     * @param location the new entity location
+     * @param lift whether the entity will be lifted by 1.975
+     * @return the packet
+     */
+    public static PacketPlayOutEntityTeleport createTeleportPacket(int id, Location location, boolean lift) {
+        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
+        s.d(id); // id
+        s.writeDouble(location.getX()); // x
+        s.writeDouble(location.getY() + (lift ? 1.975 : 0)); // y
+        s.writeDouble(location.getZ()); // z
+        s.writeByte(0); // yaw
+        s.writeByte(0); // pitch
+        s.writeBoolean(true); // on ground
+
+        try {
+            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
+            packet.a(s);
+            return packet;
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            s.release();
+        }
+
+        return null;
+    }
+}

nms/v13r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_13_R1/HologramItem.java

@@ -0,0 +1,128 @@
+package de.epiceric.shopchest.shop.hologram.v1_13_R1;
+
+import java.lang.reflect.AccessibleObject;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_13_R1.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_13_R1.DataWatcher;
+import net.minecraft.server.v1_13_R1.DataWatcherObject;
+import net.minecraft.server.v1_13_R1.Entity;
+import net.minecraft.server.v1_13_R1.EntityItem;
+import net.minecraft.server.v1_13_R1.Packet;
+import net.minecraft.server.v1_13_R1.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_13_R1.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_13_R1.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_13_R1.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private DataWatcherObject<net.minecraft.server.v1_13_R1.ItemStack> item;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        Packet<?> teleportPacket = HologramUtil.createTeleportPacket(id, location, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.register(item, getNmsItemStack()); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    @SuppressWarnings("unchecked")
+    private DataWatcher createDataWatcher() {
+        try {
+            Field fAirTicks = Entity.class.getDeclaredField("aD");
+            Field fNoGravity = Entity.class.getDeclaredField("aH");
+            Field fItem = EntityItem.class.getDeclaredField("b");
+
+            setAccessible(fAirTicks, fNoGravity, fItem);
+
+            item = (DataWatcherObject<net.minecraft.server.v1_13_R1.ItemStack>) fItem.get(null);
+            DataWatcherObject<Integer> airTicks = (DataWatcherObject<Integer>) fAirTicks.get(null);
+            DataWatcherObject<Boolean> noGravity = (DataWatcherObject<Boolean>) fNoGravity.get(null);
+
+            DataWatcher dataWatcher = new DataWatcher(null);
+            dataWatcher.register(airTicks, 300);
+            dataWatcher.register(noGravity, true);
+            dataWatcher.register(item, getNmsItemStack());
+
+            return dataWatcher;
+        } catch (ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    private net.minecraft.server.v1_13_R1.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+
+    private void setAccessible(AccessibleObject... args) {
+        Arrays.stream(args).forEach(arg -> arg.setAccessible(true));
+    }
+}

nms/v13r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_13_R1/HologramLine.java

@@ -1,31 +1,25 @@
 package de.epiceric.shopchest.shop.hologram.v1_13_R1;
 
-import java.io.IOException;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Optional;
-import java.util.UUID;
 
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_13_R1.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_13_R1.DataWatcher;
 import net.minecraft.server.v1_13_R1.DataWatcherObject;
 import net.minecraft.server.v1_13_R1.Entity;
 import net.minecraft.server.v1_13_R1.EntityArmorStand;
 import net.minecraft.server.v1_13_R1.IChatBaseComponent;
+import net.minecraft.server.v1_13_R1.IChatBaseComponent.ChatSerializer;
 import net.minecraft.server.v1_13_R1.Packet;
-import net.minecraft.server.v1_13_R1.PacketDataSerializer;
 import net.minecraft.server.v1_13_R1.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_13_R1.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_13_R1.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_13_R1.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_13_R1.PlayerConnection;
-import net.minecraft.server.v1_13_R1.IChatBaseComponent.ChatSerializer;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -46,16 +40,16 @@ public class HologramLine implements IHologramLine {
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
-        PacketPlayOutEntityTeleport packet = createTeleportPacket();
+        PacketPlayOutEntityTeleport packet = HologramUtil.createTeleportPacket(id, location, false);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, packet));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, packet));
     }
 
     @Override
@@ -71,7 +65,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.register(customName, Optional.ofNullable(ChatSerializer.b(text)));
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -85,7 +79,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -94,59 +88,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private PacketPlayOutEntityTeleport createTeleportPacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // yaw
-        s.writeByte(0); // pitch
-        s.writeBoolean(true); // on ground
-
-        try {
-            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
-            packet.a(s);
-            return packet;
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
-
-        return null;
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.a(UUID.randomUUID()); // uuid
-        s.writeByte(78); // type
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // ?
-        s.writeShort(0); // mot x
-        s.writeShort(0); // mot y
-        s.writeShort(0); // mot z
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     @SuppressWarnings("unchecked")

nms/v13r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_13_R1/HologramUtil.java

@@ -0,0 +1,114 @@
+package de.epiceric.shopchest.shop.hologram.v1_13_R1;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.UUID;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_13_R1.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_13_R1.Entity;
+import net.minecraft.server.v1_13_R1.Packet;
+import net.minecraft.server.v1_13_R1.PacketDataSerializer;
+import net.minecraft.server.v1_13_R1.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_13_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_13_R1.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id + 1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType == 78 ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.a(UUID.randomUUID()); // uuid
+        serializer.writeByte(entityType); // entity type
+        serializer.writeDouble(location.getX()); // x
+        serializer.writeDouble(location.getY() + yLift); // y
+        serializer.writeDouble(location.getZ()); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+
+    /**
+     * Creates a PacketPlayOutEntityTeleport
+     * 
+     * @param id the entity ID
+     * @param location the new entity location
+     * @param lift whether the entity will be lifted by 1.975
+     * @return the packet
+     */
+    public static PacketPlayOutEntityTeleport createTeleportPacket(int id, Location location, boolean lift) {
+        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
+        s.d(id); // id
+        s.writeDouble(location.getX()); // x
+        s.writeDouble(location.getY() + (lift ? 1.975 : 0)); // y
+        s.writeDouble(location.getZ()); // z
+        s.writeByte(0); // yaw
+        s.writeByte(0); // pitch
+        s.writeBoolean(true); // on ground
+
+        try {
+            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
+            packet.a(s);
+            return packet;
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            s.release();
+        }
+
+        return null;
+    }
+}

nms/v13r2/src/main/java/de/epiceric/shopchest/shop/hologram/v1_13_R2/HologramItem.java

@@ -0,0 +1,128 @@
+package de.epiceric.shopchest.shop.hologram.v1_13_R2;
+
+import java.lang.reflect.AccessibleObject;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_13_R2.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_13_R2.DataWatcher;
+import net.minecraft.server.v1_13_R2.DataWatcherObject;
+import net.minecraft.server.v1_13_R2.Entity;
+import net.minecraft.server.v1_13_R2.EntityItem;
+import net.minecraft.server.v1_13_R2.Packet;
+import net.minecraft.server.v1_13_R2.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_13_R2.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_13_R2.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_13_R2.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private DataWatcherObject<net.minecraft.server.v1_13_R2.ItemStack> item;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        Packet<?> teleportPacket = HologramUtil.createTeleportPacket(id, location, false);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.register(item, getNmsItemStack()); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    @SuppressWarnings("unchecked")
+    private DataWatcher createDataWatcher() {
+        try {
+            Field fAirTicks = Entity.class.getDeclaredField("aD");
+            Field fNoGravity = Entity.class.getDeclaredField("aH");
+            Field fItem = EntityItem.class.getDeclaredField("b");
+
+            setAccessible(fAirTicks, fNoGravity, fItem);
+
+            item = (DataWatcherObject<net.minecraft.server.v1_13_R2.ItemStack>) fItem.get(null);
+            DataWatcherObject<Integer> airTicks = (DataWatcherObject<Integer>) fAirTicks.get(null);
+            DataWatcherObject<Boolean> noGravity = (DataWatcherObject<Boolean>) fNoGravity.get(null);
+
+            DataWatcher dataWatcher = new DataWatcher(null);
+            dataWatcher.register(airTicks, 300);
+            dataWatcher.register(noGravity, true);
+            dataWatcher.register(item, getNmsItemStack());
+
+            return dataWatcher;
+        } catch (ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    private net.minecraft.server.v1_13_R2.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+
+    private void setAccessible(AccessibleObject... args) {
+        Arrays.stream(args).forEach(arg -> arg.setAccessible(true));
+    }
+}

nms/v13r2/src/main/java/de/epiceric/shopchest/shop/hologram/v1_13_R2/HologramLine.java

@@ -1,31 +1,25 @@
 package de.epiceric.shopchest.shop.hologram.v1_13_R2;
 
-import java.io.IOException;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Optional;
-import java.util.UUID;
 
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_13_R2.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_13_R2.DataWatcher;
 import net.minecraft.server.v1_13_R2.DataWatcherObject;
 import net.minecraft.server.v1_13_R2.Entity;
 import net.minecraft.server.v1_13_R2.EntityArmorStand;
 import net.minecraft.server.v1_13_R2.IChatBaseComponent;
+import net.minecraft.server.v1_13_R2.IChatBaseComponent.ChatSerializer;
 import net.minecraft.server.v1_13_R2.Packet;
-import net.minecraft.server.v1_13_R2.PacketDataSerializer;
 import net.minecraft.server.v1_13_R2.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_13_R2.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_13_R2.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_13_R2.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_13_R2.PlayerConnection;
-import net.minecraft.server.v1_13_R2.IChatBaseComponent.ChatSerializer;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -46,16 +40,16 @@ public class HologramLine implements IHologramLine {
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
-        PacketPlayOutEntityTeleport packet = createTeleportPacket();
+        PacketPlayOutEntityTeleport packet = HologramUtil.createTeleportPacket(id, location, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, packet));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, packet));
     }
 
     @Override
@@ -71,7 +65,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.register(customName, Optional.ofNullable(ChatSerializer.b(text)));
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -85,7 +79,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -94,59 +88,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private PacketPlayOutEntityTeleport createTeleportPacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // yaw
-        s.writeByte(0); // pitch
-        s.writeBoolean(true); // on ground
-
-        try {
-            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
-            packet.a(s);
-            return packet;
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
-
-        return null;
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.a(UUID.randomUUID()); // uuid
-        s.writeByte(78); // type
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // ?
-        s.writeShort(0); // mot x
-        s.writeShort(0); // mot y
-        s.writeShort(0); // mot z
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     @SuppressWarnings("unchecked")

nms/v13r2/src/main/java/de/epiceric/shopchest/shop/hologram/v1_13_R2/HologramUtil.java

@@ -0,0 +1,114 @@
+package de.epiceric.shopchest.shop.hologram.v1_13_R2;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.UUID;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_13_R2.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_13_R2.Entity;
+import net.minecraft.server.v1_13_R2.Packet;
+import net.minecraft.server.v1_13_R2.PacketDataSerializer;
+import net.minecraft.server.v1_13_R2.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_13_R2.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_13_R2.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id + 1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType == 78 ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.a(UUID.randomUUID()); // uuid
+        serializer.writeByte(entityType); // entity type
+        serializer.writeDouble(location.getX()); // x
+        serializer.writeDouble(location.getY() + yLift); // y
+        serializer.writeDouble(location.getZ()); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+
+    /**
+     * Creates a PacketPlayOutEntityTeleport
+     * 
+     * @param id the entity ID
+     * @param location the new entity location
+     * @param lift whether the entity will be lifted by 1.975
+     * @return the packet
+     */
+    public static PacketPlayOutEntityTeleport createTeleportPacket(int id, Location location, boolean lift) {
+        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
+        s.d(id); // id
+        s.writeDouble(location.getX()); // x
+        s.writeDouble(location.getY() + (lift ? 1.975 : 0)); // y
+        s.writeDouble(location.getZ()); // z
+        s.writeByte(0); // yaw
+        s.writeByte(0); // pitch
+        s.writeBoolean(true); // on ground
+
+        try {
+            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
+            packet.a(s);
+            return packet;
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            s.release();
+        }
+
+        return null;
+    }
+}

nms/v14r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_14_R1/HologramItem.java

@@ -0,0 +1,130 @@
+package de.epiceric.shopchest.shop.hologram.v1_14_R1;
+
+import java.lang.reflect.AccessibleObject;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_14_R1.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_14_R1.DataWatcher;
+import net.minecraft.server.v1_14_R1.DataWatcherObject;
+import net.minecraft.server.v1_14_R1.Entity;
+import net.minecraft.server.v1_14_R1.EntityItem;
+import net.minecraft.server.v1_14_R1.EntityTypes;
+import net.minecraft.server.v1_14_R1.Packet;
+import net.minecraft.server.v1_14_R1.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_14_R1.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_14_R1.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_14_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_14_R1.Vec3D;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private DataWatcherObject<net.minecraft.server.v1_14_R1.ItemStack> item;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, EntityTypes.ITEM, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, EntityTypes.ITEM, spawnPacket, location);
+
+        Packet<?> teleportPacket = HologramUtil.createTeleportPacket(id, location, false);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.register(item, getNmsItemStack()); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, new Vec3D(0, 0, 0));
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    @SuppressWarnings("unchecked")
+    private DataWatcher createDataWatcher() {
+        try {
+            Field fAirTicks = Entity.class.getDeclaredField("AIR_TICKS");
+            Field fNoGravity = Entity.class.getDeclaredField("aC");
+            Field fItem = EntityItem.class.getDeclaredField("ITEM");
+
+            setAccessible(fAirTicks, fNoGravity, fItem);
+
+            item = (DataWatcherObject<net.minecraft.server.v1_14_R1.ItemStack>) fItem.get(null);
+            DataWatcherObject<Integer> airTicks = (DataWatcherObject<Integer>) fAirTicks.get(null);
+            DataWatcherObject<Boolean> noGravity = (DataWatcherObject<Boolean>) fNoGravity.get(null);
+
+            DataWatcher dataWatcher = new DataWatcher(null);
+            dataWatcher.register(airTicks, 300);
+            dataWatcher.register(noGravity, true);
+            dataWatcher.register(item, getNmsItemStack());
+
+            return dataWatcher;
+        } catch (ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    private net.minecraft.server.v1_14_R1.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+
+    private void setAccessible(AccessibleObject... args) {
+        Arrays.stream(args).forEach(arg -> arg.setAccessible(true));
+    }
+}

nms/v14r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_14_R1/HologramLine.java

@@ -1,33 +1,26 @@
 package de.epiceric.shopchest.shop.hologram.v1_14_R1;
 
-import java.io.IOException;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Optional;
-import java.util.UUID;
 
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_14_R1.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_14_R1.DataWatcher;
 import net.minecraft.server.v1_14_R1.DataWatcherObject;
 import net.minecraft.server.v1_14_R1.Entity;
 import net.minecraft.server.v1_14_R1.EntityArmorStand;
 import net.minecraft.server.v1_14_R1.EntityTypes;
 import net.minecraft.server.v1_14_R1.IChatBaseComponent;
-import net.minecraft.server.v1_14_R1.IRegistry;
+import net.minecraft.server.v1_14_R1.IChatBaseComponent.ChatSerializer;
 import net.minecraft.server.v1_14_R1.Packet;
-import net.minecraft.server.v1_14_R1.PacketDataSerializer;
 import net.minecraft.server.v1_14_R1.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_14_R1.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_14_R1.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_14_R1.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_14_R1.PlayerConnection;
-import net.minecraft.server.v1_14_R1.IChatBaseComponent.ChatSerializer;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -48,16 +41,16 @@ public class HologramLine implements IHologramLine {
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, EntityTypes.ARMOR_STAND, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, EntityTypes.ARMOR_STAND, spawnPacket, location);
 
-        PacketPlayOutEntityTeleport packet = createTeleportPacket();
+        PacketPlayOutEntityTeleport packet = HologramUtil.createTeleportPacket(id, location, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, packet));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, packet));
     }
 
     @Override
@@ -73,7 +66,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.register(customName, Optional.ofNullable(ChatSerializer.b(text)));
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -87,7 +80,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -96,59 +89,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private PacketPlayOutEntityTeleport createTeleportPacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // yaw
-        s.writeByte(0); // pitch
-        s.writeBoolean(true); // on ground
-
-        try {
-            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
-            packet.a(s);
-            return packet;
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
-
-        return null;
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.a(UUID.randomUUID()); // uuid
-        s.d(IRegistry.ENTITY_TYPE.a(EntityTypes.ARMOR_STAND)); // type
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY()); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // ?
-        s.writeShort(0); // mot x
-        s.writeShort(0); // mot y
-        s.writeShort(0); // mot z
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     @SuppressWarnings("unchecked")

nms/v14r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_14_R1/HologramUtil.java

@@ -0,0 +1,116 @@
+package de.epiceric.shopchest.shop.hologram.v1_14_R1;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_14_R1.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_14_R1.Entity;
+import net.minecraft.server.v1_14_R1.EntityTypes;
+import net.minecraft.server.v1_14_R1.IRegistry;
+import net.minecraft.server.v1_14_R1.Packet;
+import net.minecraft.server.v1_14_R1.PacketDataSerializer;
+import net.minecraft.server.v1_14_R1.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_14_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_14_R1.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            AtomicInteger count = (AtomicInteger) entityCountField.get(null);
+            return count.incrementAndGet();
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, EntityTypes<?> entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType.equals(EntityTypes.ARMOR_STAND) ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.a(UUID.randomUUID()); // uuid
+        serializer.d(IRegistry.ENTITY_TYPE.a(entityType)); // type
+        serializer.writeDouble(location.getX()); // x
+        serializer.writeDouble(location.getY() + yLift); // y
+        serializer.writeDouble(location.getZ()); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+
+    /**
+     * Creates a PacketPlayOutEntityTeleport
+     * 
+     * @param id the entity ID
+     * @param location the new entity location
+     * @param lift whether the entity will be lifted by 1.975
+     * @return the packet
+     */
+    public static PacketPlayOutEntityTeleport createTeleportPacket(int id, Location location, boolean lift) {
+        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
+        s.d(id); // id
+        s.writeDouble(location.getX()); // x
+        s.writeDouble(location.getY() + (lift ? 1.975 : 0)); // y
+        s.writeDouble(location.getZ()); // z
+        s.writeByte(0); // yaw
+        s.writeByte(0); // pitch
+        s.writeBoolean(true); // on ground
+
+        try {
+            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
+            packet.a(s);
+            return packet;
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            s.release();
+        }
+
+        return null;
+    }
+}

nms/v15r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_15_R1/HologramItem.java

@@ -0,0 +1,130 @@
+package de.epiceric.shopchest.shop.hologram.v1_15_R1;
+
+import java.lang.reflect.AccessibleObject;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_15_R1.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_15_R1.DataWatcher;
+import net.minecraft.server.v1_15_R1.DataWatcherObject;
+import net.minecraft.server.v1_15_R1.Entity;
+import net.minecraft.server.v1_15_R1.EntityItem;
+import net.minecraft.server.v1_15_R1.EntityTypes;
+import net.minecraft.server.v1_15_R1.Packet;
+import net.minecraft.server.v1_15_R1.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_15_R1.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_15_R1.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_15_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_15_R1.Vec3D;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private DataWatcherObject<net.minecraft.server.v1_15_R1.ItemStack> item;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, EntityTypes.ITEM, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, EntityTypes.ITEM, spawnPacket, location);
+
+        Packet<?> teleportPacket = HologramUtil.createTeleportPacket(id, location, false);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.register(item, getNmsItemStack()); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, new Vec3D(0, 0, 0));
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    @SuppressWarnings("unchecked")
+    private DataWatcher createDataWatcher() {
+        try {
+            Field fAirTicks = Entity.class.getDeclaredField("AIR_TICKS");
+            Field fNoGravity = Entity.class.getDeclaredField("aC");
+            Field fItem = EntityItem.class.getDeclaredField("ITEM");
+
+            setAccessible(fAirTicks, fNoGravity, fItem);
+
+            item = (DataWatcherObject<net.minecraft.server.v1_15_R1.ItemStack>) fItem.get(null);
+            DataWatcherObject<Integer> airTicks = (DataWatcherObject<Integer>) fAirTicks.get(null);
+            DataWatcherObject<Boolean> noGravity = (DataWatcherObject<Boolean>) fNoGravity.get(null);
+
+            DataWatcher dataWatcher = new DataWatcher(null);
+            dataWatcher.register(airTicks, 300);
+            dataWatcher.register(noGravity, true);
+            dataWatcher.register(item, getNmsItemStack());
+
+            return dataWatcher;
+        } catch (ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    private net.minecraft.server.v1_15_R1.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+
+    private void setAccessible(AccessibleObject... args) {
+        Arrays.stream(args).forEach(arg -> arg.setAccessible(true));
+    }
+}

nms/v15r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_15_R1/HologramLine.java

@@ -1,33 +1,26 @@
 package de.epiceric.shopchest.shop.hologram.v1_15_R1;
 
-import java.io.IOException;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Optional;
-import java.util.UUID;
 
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_15_R1.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_15_R1.DataWatcher;
 import net.minecraft.server.v1_15_R1.DataWatcherObject;
 import net.minecraft.server.v1_15_R1.Entity;
 import net.minecraft.server.v1_15_R1.EntityArmorStand;
 import net.minecraft.server.v1_15_R1.EntityTypes;
 import net.minecraft.server.v1_15_R1.IChatBaseComponent;
-import net.minecraft.server.v1_15_R1.IRegistry;
+import net.minecraft.server.v1_15_R1.IChatBaseComponent.ChatSerializer;
 import net.minecraft.server.v1_15_R1.Packet;
-import net.minecraft.server.v1_15_R1.PacketDataSerializer;
 import net.minecraft.server.v1_15_R1.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_15_R1.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_15_R1.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_15_R1.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_15_R1.PlayerConnection;
-import net.minecraft.server.v1_15_R1.IChatBaseComponent.ChatSerializer;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -48,16 +41,16 @@ public class HologramLine implements IHologramLine {
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, EntityTypes.ARMOR_STAND, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, EntityTypes.ARMOR_STAND, spawnPacket, location);
 
-        PacketPlayOutEntityTeleport packet = createTeleportPacket();
+        PacketPlayOutEntityTeleport packet = HologramUtil.createTeleportPacket(id, location, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, packet));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, packet));
     }
 
     @Override
@@ -73,7 +66,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.register(customName, Optional.ofNullable(ChatSerializer.b(text)));
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -87,7 +80,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -96,59 +89,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private PacketPlayOutEntityTeleport createTeleportPacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // yaw
-        s.writeByte(0); // pitch
-        s.writeBoolean(true); // on ground
-
-        try {
-            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
-            packet.a(s);
-            return packet;
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
-
-        return null;
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.a(UUID.randomUUID()); // uuid
-        s.d(IRegistry.ENTITY_TYPE.a(EntityTypes.ARMOR_STAND)); // type
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY()); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // ?
-        s.writeShort(0); // mot x
-        s.writeShort(0); // mot y
-        s.writeShort(0); // mot z
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     @SuppressWarnings("unchecked")

nms/v15r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_15_R1/HologramUtil.java

@@ -0,0 +1,116 @@
+package de.epiceric.shopchest.shop.hologram.v1_15_R1;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_15_R1.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_15_R1.Entity;
+import net.minecraft.server.v1_15_R1.EntityTypes;
+import net.minecraft.server.v1_15_R1.IRegistry;
+import net.minecraft.server.v1_15_R1.Packet;
+import net.minecraft.server.v1_15_R1.PacketDataSerializer;
+import net.minecraft.server.v1_15_R1.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_15_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_15_R1.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            AtomicInteger count = (AtomicInteger) entityCountField.get(null);
+            return count.incrementAndGet();
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, EntityTypes<?> entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType.equals(EntityTypes.ARMOR_STAND) ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.a(UUID.randomUUID()); // uuid
+        serializer.d(IRegistry.ENTITY_TYPE.a(entityType)); // type
+        serializer.writeDouble(location.getX()); // x
+        serializer.writeDouble(location.getY() + yLift); // y
+        serializer.writeDouble(location.getZ()); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+
+    /**
+     * Creates a PacketPlayOutEntityTeleport
+     * 
+     * @param id the entity ID
+     * @param location the new entity location
+     * @param lift whether the entity will be lifted by 1.975
+     * @return the packet
+     */
+    public static PacketPlayOutEntityTeleport createTeleportPacket(int id, Location location, boolean lift) {
+        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
+        s.d(id); // id
+        s.writeDouble(location.getX()); // x
+        s.writeDouble(location.getY() + (lift ? 1.975 : 0)); // y
+        s.writeDouble(location.getZ()); // z
+        s.writeByte(0); // yaw
+        s.writeByte(0); // pitch
+        s.writeBoolean(true); // on ground
+
+        try {
+            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
+            packet.a(s);
+            return packet;
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            s.release();
+        }
+
+        return null;
+    }
+}

nms/v8r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_8_R1/HologramItem.java

@@ -0,0 +1,105 @@
+package de.epiceric.shopchest.shop.hologram.v1_8_R1;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_8_R1.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_8_R1.DataWatcher;
+import net.minecraft.server.v1_8_R1.MathHelper;
+import net.minecraft.server.v1_8_R1.Packet;
+import net.minecraft.server.v1_8_R1.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_8_R1.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_8_R1.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_8_R1.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_8_R1.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        int x = MathHelper.floor(location.getX() * 32d);
+        int y = MathHelper.floor(location.getY() * 32d);
+        int z = MathHelper.floor(location.getZ() * 32d);
+
+        Packet teleportPacket = new PacketPlayOutEntityTeleport(id, x, y, z, (byte) 0, (byte) 0, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.a(10, getNmsItemStack()); // item stack
+
+        Packet metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    private DataWatcher createDataWatcher() {
+        DataWatcher dataWatcher = new DataWatcher(null);
+        dataWatcher.a(0, 0); // entity flags
+        dataWatcher.a(1, (short) 300); // air ticks
+        dataWatcher.a(2, ""); // custom name
+        dataWatcher.a(3, 0); // name visible
+        dataWatcher.a(10, getNmsItemStack()); // item stack
+        return dataWatcher;
+    }
+
+    private net.minecraft.server.v1_8_R1.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+}

nms/v8r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_8_R1/HologramLine.java

@@ -1,22 +1,16 @@
 package de.epiceric.shopchest.shop.hologram.v1_8_R1;
 
-import java.util.Arrays;
-
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_8_R1.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_8_R1.DataWatcher;
 import net.minecraft.server.v1_8_R1.MathHelper;
 import net.minecraft.server.v1_8_R1.Packet;
-import net.minecraft.server.v1_8_R1.PacketDataSerializer;
 import net.minecraft.server.v1_8_R1.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_8_R1.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_8_R1.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_8_R1.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_8_R1.PlayerConnection;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -27,27 +21,27 @@ public class HologramLine implements IHologramLine {
     private String text;
 
     public HologramLine(Location location, String text) {
-        this.id = 5;
+        this.id = HologramUtil.getFreeEntityId();
         this.location = location.clone();
         this.text = text == null ? "" : text;
 
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
         int x = MathHelper.floor(location.getX() * 32d);
         int y = MathHelper.floor(location.getY() * 32d);
         int z = MathHelper.floor(location.getZ() * 32d);
 
         Packet teleportPacket = new PacketPlayOutEntityTeleport(id, x, y, z, (byte) 0, (byte) 0, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, teleportPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
     }
 
     @Override
@@ -63,7 +57,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.a(3, (byte) (this.text.isEmpty() ? 0 : 1)); // name visible
 
         Packet metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -77,7 +71,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -86,26 +80,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
-        serializer.b(id); // id
-        serializer.writeByte(78); // entity type
-        serializer.writeInt(MathHelper.floor(location.getX() * 32d)); // x
-        serializer.writeInt(MathHelper.floor(location.getY() * 32d)); // y
-        serializer.writeInt(MathHelper.floor(location.getZ() * 32d)); // z
-        serializer.writeByte(0); // pitch
-        serializer.writeByte(0); // yaw
-        serializer.writeInt(0); // has motion (?)
-        this.spawnPacket.a(serializer);
-        serializer.release();
     }
 
     private DataWatcher createDataWatcher() {

nms/v8r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_8_R1/HologramUtil.java

@@ -0,0 +1,72 @@
+package de.epiceric.shopchest.shop.hologram.v1_8_R1;
+
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_8_R1.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_8_R1.Entity;
+import net.minecraft.server.v1_8_R1.MathHelper;
+import net.minecraft.server.v1_8_R1.Packet;
+import net.minecraft.server.v1_8_R1.PacketDataSerializer;
+import net.minecraft.server.v1_8_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_8_R1.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+    
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id+1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.writeByte(entityType); // entity type
+        serializer.writeInt(MathHelper.floor(location.getX() * 32d)); // x
+        serializer.writeInt(MathHelper.floor(location.getY() * 32d)); // y
+        serializer.writeInt(MathHelper.floor(location.getZ() * 32d)); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+        spawnPacket.a(serializer);
+        serializer.release();
+    }
+}

nms/v8r2/src/main/java/de/epiceric/shopchest/shop/hologram/v1_8_R2/HologramItem.java

@@ -0,0 +1,102 @@
+package de.epiceric.shopchest.shop.hologram.v1_8_R2;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_8_R2.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_8_R2.DataWatcher;
+import net.minecraft.server.v1_8_R2.MathHelper;
+import net.minecraft.server.v1_8_R2.Packet;
+import net.minecraft.server.v1_8_R2.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_8_R2.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_8_R2.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_8_R2.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_8_R2.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        int x = MathHelper.floor(location.getX() * 32d);
+        int y = MathHelper.floor(location.getY() * 32d);
+        int z = MathHelper.floor(location.getZ() * 32d);
+
+        Packet<?> teleportPacket = new PacketPlayOutEntityTeleport(id, x, y, z, (byte) 0, (byte) 0, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.a(10, getNmsItemStack()); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    private DataWatcher createDataWatcher() {
+        DataWatcher dataWatcher = new DataWatcher(null);
+        dataWatcher.a(1, (short) 300); // air ticks
+        dataWatcher.a(10, getNmsItemStack()); // item stack
+        return dataWatcher;
+    }
+
+    private net.minecraft.server.v1_8_R2.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+}

nms/v8r2/src/main/java/de/epiceric/shopchest/shop/hologram/v1_8_R2/HologramLine.java

@@ -1,23 +1,16 @@
 package de.epiceric.shopchest.shop.hologram.v1_8_R2;
 
-import java.io.IOException;
-import java.util.Arrays;
-
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_8_R2.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_8_R2.DataWatcher;
 import net.minecraft.server.v1_8_R2.MathHelper;
 import net.minecraft.server.v1_8_R2.Packet;
-import net.minecraft.server.v1_8_R2.PacketDataSerializer;
 import net.minecraft.server.v1_8_R2.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_8_R2.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_8_R2.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_8_R2.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_8_R2.PlayerConnection;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -28,27 +21,27 @@ public class HologramLine implements IHologramLine {
     private String text;
 
     public HologramLine(Location location, String text) {
-        this.id = 5;
+        this.id = HologramUtil.getFreeEntityId();
         this.location = location.clone();
         this.text = text == null ? "" : text;
 
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
         int x = MathHelper.floor(location.getX() * 32d);
         int y = MathHelper.floor((location.getY() + 1.975) * 32d);
         int z = MathHelper.floor(location.getZ() * 32d);
 
         Packet<?> teleportPacket = new PacketPlayOutEntityTeleport(id, x, y, z, (byte) 0, (byte) 0, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, teleportPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
     }
 
     @Override
@@ -64,7 +57,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.a(3, (byte) (this.text.isEmpty() ? 0 : 1)); // name visible
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -78,7 +71,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -87,32 +80,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.b(id); // id
-        s.writeByte(78); // entity type
-        s.writeInt(MathHelper.floor(location.getX() * 32d)); // x
-        s.writeInt(MathHelper.floor((location.getY() + 1.975) * 32d)); // y
-        s.writeInt(MathHelper.floor(location.getZ() * 32d)); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // has motion (?)
-        
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     private DataWatcher createDataWatcher() {

nms/v8r2/src/main/java/de/epiceric/shopchest/shop/hologram/v1_8_R2/HologramUtil.java

@@ -0,0 +1,81 @@
+package de.epiceric.shopchest.shop.hologram.v1_8_R2;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_8_R2.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_8_R2.Entity;
+import net.minecraft.server.v1_8_R2.MathHelper;
+import net.minecraft.server.v1_8_R2.Packet;
+import net.minecraft.server.v1_8_R2.PacketDataSerializer;
+import net.minecraft.server.v1_8_R2.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_8_R2.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id + 1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType == 78 ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.writeByte(entityType); // entity type
+        serializer.writeInt(MathHelper.floor(location.getX() * 32d)); // x
+        serializer.writeInt(MathHelper.floor((location.getY() + yLift) * 32d)); // y
+        serializer.writeInt(MathHelper.floor(location.getZ() * 32d)); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+}

nms/v8r3/src/main/java/de/epiceric/shopchest/shop/hologram/v1_8_R3/HologramItem.java

@@ -0,0 +1,102 @@
+package de.epiceric.shopchest.shop.hologram.v1_8_R3;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_8_R3.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_8_R3.DataWatcher;
+import net.minecraft.server.v1_8_R3.MathHelper;
+import net.minecraft.server.v1_8_R3.Packet;
+import net.minecraft.server.v1_8_R3.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_8_R3.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_8_R3.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_8_R3.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_8_R3.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        int x = MathHelper.floor(location.getX() * 32d);
+        int y = MathHelper.floor(location.getY() * 32d);
+        int z = MathHelper.floor(location.getZ() * 32d);
+
+        Packet<?> teleportPacket = new PacketPlayOutEntityTeleport(id, x, y, z, (byte) 0, (byte) 0, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.a(10, getNmsItemStack());
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    private DataWatcher createDataWatcher() {
+        DataWatcher dataWatcher = new DataWatcher(null);
+        dataWatcher.a(1, (short) 300); // air ticks
+        dataWatcher.a(10, getNmsItemStack()); // item stack
+        return dataWatcher;
+    }
+
+    private net.minecraft.server.v1_8_R3.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+}

nms/v8r3/src/main/java/de/epiceric/shopchest/shop/hologram/v1_8_R3/HologramLine.java

@@ -1,23 +1,16 @@
 package de.epiceric.shopchest.shop.hologram.v1_8_R3;
 
-import java.io.IOException;
-import java.util.Arrays;
-
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_8_R3.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_8_R3.DataWatcher;
 import net.minecraft.server.v1_8_R3.MathHelper;
 import net.minecraft.server.v1_8_R3.Packet;
-import net.minecraft.server.v1_8_R3.PacketDataSerializer;
 import net.minecraft.server.v1_8_R3.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_8_R3.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_8_R3.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_8_R3.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_8_R3.PlayerConnection;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -35,20 +28,20 @@ public class HologramLine implements IHologramLine {
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
         int x = MathHelper.floor(location.getX() * 32d);
         int y = MathHelper.floor((location.getY() + 1.975) * 32d);
         int z = MathHelper.floor(location.getZ() * 32d);
 
         Packet<?> teleportPacket = new PacketPlayOutEntityTeleport(id, x, y, z, (byte) 0, (byte) 0, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, teleportPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
     }
 
     @Override
@@ -64,7 +57,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.a(3, (byte) (this.text.isEmpty() ? 0 : 1)); // name visible
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -78,7 +71,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -87,32 +80,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.b(id); // id
-        s.writeByte(78); // entity type
-        s.writeInt(MathHelper.floor(location.getX() * 32d)); // x
-        s.writeInt(MathHelper.floor((location.getY() + 1.975) * 32d)); // y
-        s.writeInt(MathHelper.floor(location.getZ() * 32d)); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // has motion (?)
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     private DataWatcher createDataWatcher() {

nms/v8r3/src/main/java/de/epiceric/shopchest/shop/hologram/v1_8_R3/HologramUtil.java

@@ -0,0 +1,81 @@
+package de.epiceric.shopchest.shop.hologram.v1_8_R3;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_8_R3.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_8_R3.Entity;
+import net.minecraft.server.v1_8_R3.MathHelper;
+import net.minecraft.server.v1_8_R3.Packet;
+import net.minecraft.server.v1_8_R3.PacketDataSerializer;
+import net.minecraft.server.v1_8_R3.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_8_R3.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id + 1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType == 78 ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.writeByte(entityType); // entity type
+        serializer.writeInt(MathHelper.floor(location.getX() * 32d)); // x
+        serializer.writeInt(MathHelper.floor((location.getY() + yLift) * 32d)); // y
+        serializer.writeInt(MathHelper.floor(location.getZ() * 32d)); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+}

nms/v9r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_9_R1/HologramItem.java

@@ -0,0 +1,127 @@
+package de.epiceric.shopchest.shop.hologram.v1_9_R1;
+
+import java.lang.reflect.AccessibleObject;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import com.google.common.base.Optional;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_9_R1.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_9_R1.DataWatcher;
+import net.minecraft.server.v1_9_R1.DataWatcherObject;
+import net.minecraft.server.v1_9_R1.Entity;
+import net.minecraft.server.v1_9_R1.EntityItem;
+import net.minecraft.server.v1_9_R1.Packet;
+import net.minecraft.server.v1_9_R1.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_9_R1.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_9_R1.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_9_R1.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private DataWatcherObject<Optional<net.minecraft.server.v1_9_R1.ItemStack>> item;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        Packet<?> teleportPacket = HologramUtil.createTeleportPacket(id, location, false);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.register(item, Optional.of(getNmsItemStack())); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    @SuppressWarnings("unchecked")
+    private DataWatcher createDataWatcher() {
+        try {
+            Field fAirTicks = Entity.class.getDeclaredField("ay");
+            Field fItem = EntityItem.class.getDeclaredField("c");
+
+            setAccessible(fAirTicks, fItem);
+
+            item = (DataWatcherObject<Optional<net.minecraft.server.v1_9_R1.ItemStack>>) fItem.get(null);
+            DataWatcherObject<Integer> airTicks = (DataWatcherObject<Integer>) fAirTicks.get(null);
+
+            DataWatcher dataWatcher = new DataWatcher(null);
+            dataWatcher.register(airTicks, 300);
+            dataWatcher.register(item, Optional.of(getNmsItemStack()));
+
+            return dataWatcher;
+        } catch (ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    private net.minecraft.server.v1_9_R1.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+
+    private void setAccessible(AccessibleObject... args) {
+        Arrays.stream(args).forEach(arg -> arg.setAccessible(true));
+    }
+}

nms/v9r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_9_R1/HologramLine.java

@@ -1,30 +1,24 @@
 package de.epiceric.shopchest.shop.hologram.v1_9_R1;
 
-import java.io.IOException;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Optional;
-import java.util.UUID;
 
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_9_R1.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_9_R1.DataWatcher;
 import net.minecraft.server.v1_9_R1.DataWatcherObject;
 import net.minecraft.server.v1_9_R1.Entity;
 import net.minecraft.server.v1_9_R1.EntityArmorStand;
 import net.minecraft.server.v1_9_R1.IChatBaseComponent;
 import net.minecraft.server.v1_9_R1.Packet;
-import net.minecraft.server.v1_9_R1.PacketDataSerializer;
 import net.minecraft.server.v1_9_R1.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_9_R1.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_9_R1.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_9_R1.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_9_R1.PlayerConnection;
 
 public class HologramLine implements IHologramLine {
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -45,16 +39,16 @@ public class HologramLine implements IHologramLine {
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
-        PacketPlayOutEntityTeleport packet = createTeleportPacket();
+        PacketPlayOutEntityTeleport packet = HologramUtil.createTeleportPacket(id, location, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, packet));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, packet));
     }
 
     @Override
@@ -70,7 +64,7 @@ public class HologramLine implements IHologramLine {
         dataWatcher.register(customName, text);
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -84,7 +78,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -93,59 +87,7 @@ public class HologramLine implements IHologramLine {
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private PacketPlayOutEntityTeleport createTeleportPacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // yaw
-        s.writeByte(0); // pitch
-        s.writeBoolean(true); // on ground
-
-        try {
-            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
-            packet.a(s);
-            return packet;
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
-
-        return null;
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.a(UUID.randomUUID()); // uuid
-        s.writeByte(78); // type
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // ?
-        s.writeShort(0); // mot x
-        s.writeShort(0); // mot y
-        s.writeShort(0); // mot z
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     @SuppressWarnings("unchecked")

nms/v9r1/src/main/java/de/epiceric/shopchest/shop/hologram/v1_9_R1/HologramUtil.java

@@ -0,0 +1,114 @@
+package de.epiceric.shopchest.shop.hologram.v1_9_R1;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.UUID;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_9_R1.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_9_R1.Entity;
+import net.minecraft.server.v1_9_R1.Packet;
+import net.minecraft.server.v1_9_R1.PacketDataSerializer;
+import net.minecraft.server.v1_9_R1.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_9_R1.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_9_R1.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id + 1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType == 78 ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.a(UUID.randomUUID()); // uuid
+        serializer.writeByte(entityType); // entity type
+        serializer.writeDouble(location.getX()); // x
+        serializer.writeDouble(location.getY() + yLift); // y
+        serializer.writeDouble(location.getZ()); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+
+    /**
+     * Creates a PacketPlayOutEntityTeleport
+     * 
+     * @param id the entity ID
+     * @param location the new entity location
+     * @param lift whether the entity will be lifted by 1.975
+     * @return the packet
+     */
+    public static PacketPlayOutEntityTeleport createTeleportPacket(int id, Location location, boolean lift) {
+        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
+        s.d(id); // id
+        s.writeDouble(location.getX()); // x
+        s.writeDouble(location.getY() + (lift ? 1.975 : 0)); // y
+        s.writeDouble(location.getZ()); // z
+        s.writeByte(0); // yaw
+        s.writeByte(0); // pitch
+        s.writeBoolean(true); // on ground
+
+        try {
+            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
+            packet.a(s);
+            return packet;
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            s.release();
+        }
+
+        return null;
+    }
+}

nms/v9r2/src/main/java/de/epiceric/shopchest/shop/hologram/v1_9_R2/HologramItem.java

@@ -0,0 +1,127 @@
+package de.epiceric.shopchest.shop.hologram.v1_9_R2;
+
+import java.lang.reflect.AccessibleObject;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+
+import com.google.common.base.Optional;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_9_R2.inventory.CraftItemStack;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import de.epiceric.shopchest.shop.hologram.IHologramItem;
+import net.minecraft.server.v1_9_R2.DataWatcher;
+import net.minecraft.server.v1_9_R2.DataWatcherObject;
+import net.minecraft.server.v1_9_R2.Entity;
+import net.minecraft.server.v1_9_R2.EntityItem;
+import net.minecraft.server.v1_9_R2.Packet;
+import net.minecraft.server.v1_9_R2.PacketPlayOutEntityDestroy;
+import net.minecraft.server.v1_9_R2.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_9_R2.PacketPlayOutEntityVelocity;
+import net.minecraft.server.v1_9_R2.PacketPlayOutSpawnEntity;
+
+public class HologramItem implements IHologramItem {
+    private PacketPlayOutSpawnEntity spawnPacket;
+    private DataWatcher dataWatcher;
+
+    private DataWatcherObject<Optional<net.minecraft.server.v1_9_R2.ItemStack>> item;
+
+    private int id;
+    private Location location;
+    private ItemStack itemStack;
+
+    public HologramItem(Location location, ItemStack itemStack) {
+        this.id = HologramUtil.getFreeEntityId();
+        this.location = location.clone();
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        this.spawnPacket = new PacketPlayOutSpawnEntity();
+        this.dataWatcher = createDataWatcher();
+
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+    }
+
+    @Override
+    public void setLocation(Location location) {
+        this.location = location.clone();
+        HologramUtil.updateSpawnPacket(id, 2, spawnPacket, location);
+
+        Packet<?> teleportPacket = HologramUtil.createTeleportPacket(id, location, false);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, teleportPacket));
+    }
+
+    @Override
+    public Location getLocation() {
+        return this.location.clone();
+    }
+
+    @Override
+    public void setItemStack(ItemStack itemStack) {
+        this.itemStack = itemStack.clone();
+        this.itemStack.setAmount(1);
+
+        dataWatcher.register(item, Optional.of(getNmsItemStack())); // item stack
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
+    }
+
+    @Override
+    public ItemStack getItemStack() {
+        return this.itemStack.clone();
+    }
+
+    @Override
+    public void showPlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
+        Packet<?> velocityPacket = new PacketPlayOutEntityVelocity(id, 0, 0, 0);
+        HologramUtil.sendPackets(player, spawnPacket, metadataPacket, velocityPacket);
+    }
+
+    @Override
+    public void hidePlayer(Player player) {
+        if (player == null || !player.isOnline()) {
+            return;
+        }
+
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
+    }
+
+    @SuppressWarnings("unchecked")
+    private DataWatcher createDataWatcher() {
+        try {
+            Field fAirTicks = Entity.class.getDeclaredField("az");
+            Field fItem = EntityItem.class.getDeclaredField("c");
+
+            setAccessible(fAirTicks, fItem);
+
+            item = (DataWatcherObject<Optional<net.minecraft.server.v1_9_R2.ItemStack>>) fItem.get(null);
+            DataWatcherObject<Integer> airTicks = (DataWatcherObject<Integer>) fAirTicks.get(null);
+
+            DataWatcher dataWatcher = new DataWatcher(null);
+            dataWatcher.register(airTicks, 300);
+            dataWatcher.register(item, Optional.of(getNmsItemStack()));
+
+            return dataWatcher;
+        } catch (ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    private net.minecraft.server.v1_9_R2.ItemStack getNmsItemStack() {
+        return CraftItemStack.asNMSCopy(itemStack);
+    }
+
+    private void setAccessible(AccessibleObject... args) {
+        Arrays.stream(args).forEach(arg -> arg.setAccessible(true));
+    }
+}

nms/v9r2/src/main/java/de/epiceric/shopchest/shop/hologram/v1_9_R2/HologramLine.java

@@ -1,30 +1,24 @@
 package de.epiceric.shopchest.shop.hologram.v1_9_R2;
 
-import java.io.IOException;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Optional;
-import java.util.UUID;
 
 import org.bukkit.Location;
-import org.bukkit.craftbukkit.v1_9_R2.entity.CraftPlayer;
 import org.bukkit.entity.Player;
 
 import de.epiceric.shopchest.shop.hologram.IHologramLine;
-import io.netty.buffer.Unpooled;
 import net.minecraft.server.v1_9_R2.DataWatcher;
 import net.minecraft.server.v1_9_R2.DataWatcherObject;
 import net.minecraft.server.v1_9_R2.Entity;
 import net.minecraft.server.v1_9_R2.EntityArmorStand;
 import net.minecraft.server.v1_9_R2.IChatBaseComponent;
 import net.minecraft.server.v1_9_R2.Packet;
-import net.minecraft.server.v1_9_R2.PacketDataSerializer;
 import net.minecraft.server.v1_9_R2.PacketPlayOutEntityDestroy;
 import net.minecraft.server.v1_9_R2.PacketPlayOutEntityMetadata;
 import net.minecraft.server.v1_9_R2.PacketPlayOutEntityTeleport;
 import net.minecraft.server.v1_9_R2.PacketPlayOutSpawnEntity;
-import net.minecraft.server.v1_9_R2.PlayerConnection;
 
 public class HologramLine implements IHologramLine{
     private PacketPlayOutSpawnEntity spawnPacket;
@@ -45,16 +39,16 @@ public class HologramLine implements IHologramLine{
         this.spawnPacket = new PacketPlayOutSpawnEntity();
         this.dataWatcher = createDataWatcher();
 
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
     }
 
     @Override
     public void setLocation(Location location) {
         this.location = location.clone();
-        updatePacket();
+        HologramUtil.updateSpawnPacket(id, 78, spawnPacket, location);
 
-        PacketPlayOutEntityTeleport packet = createTeleportPacket();
+        PacketPlayOutEntityTeleport packet = HologramUtil.createTeleportPacket(id, location, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, packet));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, packet));
     }
 
     @Override
@@ -70,7 +64,7 @@ public class HologramLine implements IHologramLine{
         dataWatcher.register(customName, text);
 
         Packet<?> metadataPacket = new PacketPlayOutEntityMetadata(id, dataWatcher, true);
-        location.getWorld().getPlayers().forEach(player -> sendPackets(player, metadataPacket));
+        location.getWorld().getPlayers().forEach(player -> HologramUtil.sendPackets(player, metadataPacket));
     }
 
     @Override
@@ -84,7 +78,7 @@ public class HologramLine implements IHologramLine{
             return;
         }
 
-        sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
+        HologramUtil.sendPackets(player, spawnPacket, new PacketPlayOutEntityMetadata(id, dataWatcher, true));
     }
 
     @Override
@@ -93,59 +87,7 @@ public class HologramLine implements IHologramLine{
             return;
         }
 
-        sendPackets(player, new PacketPlayOutEntityDestroy(id));
+        HologramUtil.sendPackets(player, new PacketPlayOutEntityDestroy(id));
-    }
-
-    private void sendPackets(Player player, Packet<?>... packets) {
-        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
-        Arrays.stream(packets).forEach(packet -> con.sendPacket(packet));
-    }
-
-    private PacketPlayOutEntityTeleport createTeleportPacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // yaw
-        s.writeByte(0); // pitch
-        s.writeBoolean(true); // on ground
-
-        try {
-            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
-            packet.a(s);
-            return packet;
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
-
-        return null;
-    }
-
-    private void updatePacket() {
-        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
-        s.d(id); // id
-        s.a(UUID.randomUUID()); // uuid
-        s.writeByte(78); // type
-        s.writeDouble(location.getX()); // x
-        s.writeDouble(location.getY() + 1.975); // y
-        s.writeDouble(location.getZ()); // z
-        s.writeByte(0); // pitch
-        s.writeByte(0); // yaw
-        s.writeInt(0); // ?
-        s.writeShort(0); // mot x
-        s.writeShort(0); // mot y
-        s.writeShort(0); // mot z
-
-        try {
-            spawnPacket.a(s);
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            s.release();
-        }
     }
 
     @SuppressWarnings("unchecked")

nms/v9r2/src/main/java/de/epiceric/shopchest/shop/hologram/v1_9_R2/HologramUtil.java

@@ -0,0 +1,114 @@
+package de.epiceric.shopchest.shop.hologram.v1_9_R2;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.UUID;
+
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.v1_9_R2.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.server.v1_9_R2.Entity;
+import net.minecraft.server.v1_9_R2.Packet;
+import net.minecraft.server.v1_9_R2.PacketDataSerializer;
+import net.minecraft.server.v1_9_R2.PacketPlayOutEntityTeleport;
+import net.minecraft.server.v1_9_R2.PacketPlayOutSpawnEntity;
+import net.minecraft.server.v1_9_R2.PlayerConnection;
+
+public class HologramUtil {
+    private HologramUtil() {
+    }
+
+    /**
+     * Gets an unused entity ID to be used for hologram lines and items
+     * 
+     * @return an unused entity ID or -1 if an error occurred
+     */
+    public static int getFreeEntityId() {
+        try {
+            Field entityCountField = Entity.class.getDeclaredField("entityCount");
+            entityCountField.setAccessible(true);
+            int id = entityCountField.getInt(null);
+            entityCountField.setInt(null, id + 1);
+            return id;
+        } catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+
+    /**
+     * Sends the given packets to the given player
+     * 
+     * @param player the player to send the packets to
+     * @param packets the packets to send
+     */
+    public static void sendPackets(Player player, Packet<?>... packets) {
+        PlayerConnection con = ((CraftPlayer) player).getHandle().playerConnection;
+        Arrays.stream(packets).forEach(con::sendPacket);
+    }
+
+    /**
+     * Updates the PacketPlayOutSpawnEntity data to include the correct location
+     * 
+     * @param id the entity ID
+     * @param entityType the entity type
+     * @param spawnPacket the packet
+     * @param location the entity's location
+     */
+    public static void updateSpawnPacket(int id, int entityType, PacketPlayOutSpawnEntity spawnPacket, Location location) {
+        double yLift = entityType == 78 ? 1.975 : 0;
+
+        PacketDataSerializer serializer = new PacketDataSerializer(Unpooled.buffer());
+        serializer.b(id); // id
+        serializer.a(UUID.randomUUID()); // uuid
+        serializer.writeByte(entityType); // entity type
+        serializer.writeDouble(location.getX()); // x
+        serializer.writeDouble(location.getY() + yLift); // y
+        serializer.writeDouble(location.getZ()); // z
+        serializer.writeByte(0); // pitch
+        serializer.writeByte(0); // yaw
+        serializer.writeInt(0); // has motion (?)
+
+        try {
+            spawnPacket.a(serializer);
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            serializer.release();
+        }
+    }
+
+    /**
+     * Creates a PacketPlayOutEntityTeleport
+     * 
+     * @param id the entity ID
+     * @param location the new entity location
+     * @param lift whether the entity will be lifted by 1.975
+     * @return the packet
+     */
+    public static PacketPlayOutEntityTeleport createTeleportPacket(int id, Location location, boolean lift) {
+        PacketDataSerializer s = new PacketDataSerializer(Unpooled.buffer());
+        s.d(id); // id
+        s.writeDouble(location.getX()); // x
+        s.writeDouble(location.getY() + (lift ? 1.975 : 0)); // y
+        s.writeDouble(location.getZ()); // z
+        s.writeByte(0); // yaw
+        s.writeByte(0); // pitch
+        s.writeBoolean(true); // on ground
+
+        try {
+            PacketPlayOutEntityTeleport packet = new PacketPlayOutEntityTeleport();
+            packet.a(s);
+            return packet;
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            s.release();
+        }
+
+        return null;
+    }
+}