Added InstanceContainer#saveInstance to save its SerializableData + its uniqueId

src/main/java/net/minestom/server/data/DataManager.java

@@ -10,6 +10,7 @@ import net.minestom.server.utils.validate.Check;
 
 import java.util.HashMap;
 import java.util.Map;
+import java.util.UUID;
 
 public class DataManager {
 
@@ -43,6 +44,8 @@ public class DataManager {
         registerType(String.class, new StringData());
         registerType(String[].class, new StringArrayData());
 
+        registerType(UUID.class, new UuidType());
+
         registerType(SerializableData.class, new SerializableDataData());
 
         registerType(ItemStack.class, new ItemStackData());

src/main/java/net/minestom/server/data/type/UuidType.java

@@ -0,0 +1,19 @@
+package net.minestom.server.data.type;
+
+import net.minestom.server.data.DataType;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
+
+import java.util.UUID;
+
+public class UuidType extends DataType<UUID> {
+    @Override
+    public void encode(PacketWriter packetWriter, UUID value) {
+        packetWriter.writeUuid(value);
+    }
+
+    @Override
+    public UUID decode(PacketReader packetReader) {
+        return packetReader.readUuid();
+    }
+}

src/main/java/net/minestom/server/instance/Instance.java

@@ -51,7 +51,7 @@ public abstract class Instance implements BlockModifier, EventHandler, DataConta
     protected Set<ExperienceOrb> experienceOrbs = new CopyOnWriteArraySet<>();
     // Entities per chunk
     protected Map<Long, Set<Entity>> chunkEntities = new ConcurrentHashMap<>();
-    private UUID uniqueId;
+    protected UUID uniqueId;
 
     private Data data;
     private ExplosionSupplier explosionSupplier;

src/main/java/net/minestom/server/instance/InstanceContainer.java

@@ -3,6 +3,7 @@ package net.minestom.server.instance;
 import io.netty.buffer.ByteBuf;
 import net.minestom.server.MinecraftServer;
 import net.minestom.server.data.Data;
+import net.minestom.server.data.SerializableData;
 import net.minestom.server.entity.Player;
 import net.minestom.server.event.player.PlayerBlockBreakEvent;
 import net.minestom.server.instance.batch.BlockBatch;
@@ -38,8 +39,12 @@ import java.util.function.Consumer;
 /**
  * InstanceContainer is an instance that contains chunks in contrary to SharedInstance.
  */
+// TODO save data + other things such as UUID
 public class InstanceContainer extends Instance {
 
+    private static final String UUID_KEY = "uuid";
+    private static final String DATA_KEY = "data";
+
     private StorageFolder storageFolder;
 
     private List<SharedInstance> sharedInstances = new CopyOnWriteArrayList<>();
@@ -54,7 +59,16 @@ public class InstanceContainer extends Instance {
 
     public InstanceContainer(UUID uniqueId, Dimension dimension, StorageFolder storageFolder) {
         super(uniqueId, dimension);
+
         this.storageFolder = storageFolder;
+
+        if (storageFolder == null)
+            return;
+        // Retrieve instance data
+        this.uniqueId = storageFolder.getOrDefault(UUID_KEY, UUID.class, uniqueId);
+
+        Data data = storageFolder.getOrDefault(DATA_KEY, SerializableData.class, null);
+        setData(data);
     }
 
     @Override
@@ -309,6 +323,27 @@ public class InstanceContainer extends Instance {
         return ChunkUtils.isChunkUnloaded(chunk) ? null : chunk;
     }
 
+    /**
+     * Save the instance ({@link #getUniqueId()} {@link #getData()}) and call {@link #saveChunksToStorageFolder(Runnable)}
+     * <p>
+     * WARNING: {@link #getData()} needs to be a {@link SerializableData} in order to be saved
+     *
+     * @param callback the callback
+     */
+    public void saveInstance(Runnable callback) {
+        Check.notNull(getStorageFolder(), "You cannot save the instance if no StorageFolder has been defined");
+
+        this.storageFolder.set(UUID_KEY, getUniqueId(), UUID.class);
+        Data data = getData();
+        if (data != null) {
+            Check.stateCondition(!(data instanceof SerializableData),
+                    "Instance#getData needs to be a SerializableData in order to be saved");
+            this.storageFolder.set(DATA_KEY, (SerializableData) getData(), SerializableData.class);
+        }
+
+        saveChunksToStorageFolder(callback);
+    }
+
     @Override
     public void saveChunkToStorageFolder(Chunk chunk, Runnable callback) {
         Check.notNull(getStorageFolder(), "You cannot save the chunk if no StorageFolder has been defined");

src/main/java/net/minestom/server/network/packet/PacketReader.java

@@ -7,6 +7,8 @@ import net.minestom.server.utils.BlockPosition;
 import net.minestom.server.utils.SerializerUtils;
 import net.minestom.server.utils.Utils;
 
+import java.util.UUID;
+
 public class PacketReader {
 
     private ByteBuf buffer;
@@ -90,6 +92,12 @@ public class PacketReader {
         return SerializerUtils.longToBlockPosition(value);
     }
 
+    public UUID readUuid() {
+        long most = readLong();
+        long least = readLong();
+        return new UUID(most, least);
+    }
+
     public ItemStack readSlot() {
         return Utils.readItemStack(this);
     }

src/main/java/net/minestom/server/storage/StorageFolder.java

@@ -32,7 +32,7 @@ public class StorageFolder {
 
         this.storageSystem.open(folderPath);
     }
-
+    
     public byte[] get(String key) {
         return storageSystem.get(key);
     }