Prevent retrieving null managers before their initialization and added annotations in ConnectionManager

src/main/java/net/minestom/server/MinecraftServer.java

@@ -50,12 +50,14 @@ import net.minestom.server.utils.validate.Check;
 import net.minestom.server.world.Difficulty;
 import net.minestom.server.world.DimensionTypeManager;
 import net.minestom.server.world.biomes.BiomeManager;
+import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
 import java.net.Proxy;
 import java.security.KeyPair;
+import java.util.Objects;
 
 /**
  * The main server class used to start the server and retrieve all the managers.
@@ -64,6 +66,7 @@ import java.security.KeyPair;
  * You should register all of your dimensions, biomes, commands, events, etc... in-between.
  */
 public class MinecraftServer {
+
     @Getter
     private final static Logger LOGGER = LoggerFactory.getLogger(MinecraftServer.class);
 
@@ -134,6 +137,7 @@ public class MinecraftServer {
     private static MinecraftServer minecraftServer;
 
     // Data
+    private static boolean initialized;
     private static boolean started;
 
     private static int chunkViewDistance = 10;
@@ -207,6 +211,8 @@ public class MinecraftServer {
             LOGGER.error("An error happened during resource gathering. Minestom will attempt to load anyway, but things may not work, and crashes can happen.", e);
         }
 
+        initialized = true;
+
         minecraftServer = new MinecraftServer();
 
         return minecraftServer;
@@ -283,6 +289,7 @@ public class MinecraftServer {
      * @return the packet listener manager
      */
     public static PacketListenerManager getPacketListenerManager() {
+        checkInitStatus(packetListenerManager);
         return packetListenerManager;
     }
 
@@ -292,6 +299,7 @@ public class MinecraftServer {
      * @return the netty server
      */
     public static NettyServer getNettyServer() {
+        checkInitStatus(nettyServer);
         return nettyServer;
     }
 
@@ -301,6 +309,7 @@ public class MinecraftServer {
      * @return the instance manager
      */
     public static InstanceManager getInstanceManager() {
+        checkInitStatus(instanceManager);
         return instanceManager;
     }
 
@@ -310,6 +319,7 @@ public class MinecraftServer {
      * @return the block manager
      */
     public static BlockManager getBlockManager() {
+        checkInitStatus(blockManager);
         return blockManager;
     }
 
@@ -319,6 +329,7 @@ public class MinecraftServer {
      * @return the entity manager
      */
     public static EntityManager getEntityManager() {
+        checkInitStatus(entityManager);
         return entityManager;
     }
 
@@ -328,6 +339,7 @@ public class MinecraftServer {
      * @return the command manager
      */
     public static CommandManager getCommandManager() {
+        checkInitStatus(commandManager);
         return commandManager;
     }
 
@@ -337,6 +349,7 @@ public class MinecraftServer {
      * @return the recipe manager
      */
     public static RecipeManager getRecipeManager() {
+        checkInitStatus(recipeManager);
         return recipeManager;
     }
 
@@ -346,6 +359,7 @@ public class MinecraftServer {
      * @return the storage manager
      */
     public static StorageManager getStorageManager() {
+        checkInitStatus(storageManager);
         return storageManager;
     }
 
@@ -355,6 +369,7 @@ public class MinecraftServer {
      * @return the data manager
      */
     public static DataManager getDataManager() {
+        checkInitStatus(dataManager);
         return dataManager;
     }
 
@@ -364,6 +379,7 @@ public class MinecraftServer {
      * @return the team manager
      */
     public static TeamManager getTeamManager() {
+        checkInitStatus(teamManager);
         return teamManager;
     }
 
@@ -373,6 +389,7 @@ public class MinecraftServer {
      * @return the scheduler manager
      */
     public static SchedulerManager getSchedulerManager() {
+        checkInitStatus(schedulerManager);
         return schedulerManager;
     }
 
@@ -382,6 +399,7 @@ public class MinecraftServer {
      * @return the benchmark manager
      */
     public static BenchmarkManager getBenchmarkManager() {
+        checkInitStatus(benchmarkManager);
         return benchmarkManager;
     }
 
@@ -391,6 +409,7 @@ public class MinecraftServer {
      * @return the connection manager
      */
     public static ConnectionManager getConnectionManager() {
+        checkInitStatus(connectionManager);
         return connectionManager;
     }
 
@@ -475,6 +494,7 @@ public class MinecraftServer {
      * @return the response data consumer
      */
     public static ResponseDataConsumer getResponseDataConsumer() {
+        checkInitStatus(responseDataConsumer);
         return responseDataConsumer;
     }
 
@@ -484,6 +504,7 @@ public class MinecraftServer {
      * @return the loot table manager
      */
     public static LootTableManager getLootTableManager() {
+        checkInitStatus(lootTableManager);
         return lootTableManager;
     }
 
@@ -493,6 +514,7 @@ public class MinecraftServer {
      * @return the dimension manager
      */
     public static DimensionTypeManager getDimensionTypeManager() {
+        checkInitStatus(dimensionTypeManager);
         return dimensionTypeManager;
     }
 
@@ -502,6 +524,7 @@ public class MinecraftServer {
      * @return the biome manager
      */
     public static BiomeManager getBiomeManager() {
+        checkInitStatus(biomeManager);
         return biomeManager;
     }
 
@@ -511,6 +534,7 @@ public class MinecraftServer {
      * @return the advancement manager
      */
     public static AdvancementManager getAdvancementManager() {
+        checkInitStatus(advancementManager);
         return advancementManager;
     }
 
@@ -520,6 +544,7 @@ public class MinecraftServer {
      * @return the extension manager
      */
     public static ExtensionManager getExtensionManager() {
+        checkInitStatus(extensionManager);
         return extensionManager;
     }
 
@@ -529,6 +554,7 @@ public class MinecraftServer {
      * @return the tag manager
      */
     public static TagManager getTagManager() {
+        checkInitStatus(tagManager);
         return tagManager;
     }
 
@@ -538,6 +564,7 @@ public class MinecraftServer {
      * @return the update manager
      */
     public static UpdateManager getUpdateManager() {
+        checkInitStatus(updateManager);
         return updateManager;
     }
 
@@ -549,6 +576,9 @@ public class MinecraftServer {
      * @param responseDataConsumer the response data consumer, can be null
      */
     public void start(String address, int port, ResponseDataConsumer responseDataConsumer) {
+        Check.stateCondition(!initialized, "#start can only be called after #init");
+        Check.stateCondition(started, "The server is already started");
+
         LOGGER.info("Starting Minestom server.");
         MinecraftServer.responseDataConsumer = responseDataConsumer;
         updateManager.start();
@@ -592,4 +622,10 @@ public class MinecraftServer {
         LOGGER.info("Minestom server stopped successfully.");
     }
 
+    private static void checkInitStatus(@Nullable Object object) {
+        Check.stateCondition(Objects.isNull(object),
+                "You cannot access the manager before MinecraftServer#init, " +
+                        "if you are developing an extension be sure to retrieve them at least after Extension#preInitialize");
+    }
+
 }

src/main/java/net/minestom/server/network/ConnectionManager.java

@@ -7,6 +7,8 @@ import net.minestom.server.listener.manager.PacketConsumer;
 import net.minestom.server.network.packet.client.login.LoginStartPacket;
 import net.minestom.server.network.packet.server.play.ChatMessagePacket;
 import net.minestom.server.network.player.PlayerConnection;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.*;
 import java.util.concurrent.CopyOnWriteArrayList;
@@ -37,7 +39,7 @@ public final class ConnectionManager {
      * @param connection the player connection
      * @return the player linked to the connection
      */
-    public Player getPlayer(PlayerConnection connection) {
+    public Player getPlayer(@NotNull PlayerConnection connection) {
         return connectionPlayerMap.get(connection);
     }
 
@@ -46,6 +48,7 @@ public final class ConnectionManager {
      *
      * @return an unmodifiable collection containing all the online players
      */
+    @NotNull
     public Collection<Player> getOnlinePlayers() {
         return Collections.unmodifiableCollection(players);
     }
@@ -56,9 +59,10 @@ public final class ConnectionManager {
      * This can cause issue if two or more players have the same username.
      *
      * @param username the player username (ignoreCase)
-     * @return the first player who validate the username condition
+     * @return the first player who validate the username condition, null if none was found
      */
-    public Player getPlayer(String username) {
+    @Nullable
+    public Player getPlayer(@NotNull String username) {
         for (Player player : getOnlinePlayers()) {
             if (player.getUsername().equalsIgnoreCase(username))
                 return player;
@@ -72,9 +76,10 @@ public final class ConnectionManager {
      * This can cause issue if two or more players have the same UUID.
      *
      * @param uuid the player UUID
-     * @return the first player who validate the UUID condition
+     * @return the first player who validate the UUID condition, null if none was found
      */
-    public Player getPlayer(UUID uuid) {
+    @Nullable
+    public Player getPlayer(@NotNull UUID uuid) {
         for (Player player : getOnlinePlayers()) {
             if (player.getUuid().equals(uuid))
                 return player;
@@ -88,7 +93,7 @@ public final class ConnectionManager {
      * @param jsonMessage the message to send, probably a {@link net.minestom.server.chat.ColoredText} or {@link net.minestom.server.chat.RichMessage}
      * @param condition   the condition to receive the message
      */
-    public void broadcastMessage(JsonMessage jsonMessage, Function<Player, Boolean> condition) {
+    public void broadcastMessage(@NotNull JsonMessage jsonMessage, @Nullable Function<Player, Boolean> condition) {
         final Collection<Player> recipients = getRecipients(condition);
 
         if (!recipients.isEmpty()) {
@@ -102,17 +107,17 @@ public final class ConnectionManager {
      *
      * @param jsonMessage the message to send, probably a {@link net.minestom.server.chat.ColoredText} or {@link net.minestom.server.chat.RichMessage}
      */
-    public void broadcastMessage(JsonMessage jsonMessage) {
+    public void broadcastMessage(@NotNull JsonMessage jsonMessage) {
         broadcastMessage(jsonMessage, null);
     }
 
-    private void broadcastJson(String json, Collection<Player> recipients) {
+    private void broadcastJson(@NotNull String json, @NotNull Collection<Player> recipients) {
         ChatMessagePacket chatMessagePacket =
                 new ChatMessagePacket(json, ChatMessagePacket.Position.SYSTEM_MESSAGE);
         PacketWriterUtils.writeAndSend(recipients, chatMessagePacket);
     }
 
-    private Collection<Player> getRecipients(Function<Player, Boolean> condition) {
+    private Collection<Player> getRecipients(@Nullable Function<Player, Boolean> condition) {
         Collection<Player> recipients;
 
         // Get the recipients
@@ -135,6 +140,7 @@ public final class ConnectionManager {
      *
      * @return an unmodifiable list of packet's consumers
      */
+    @NotNull
     public List<PacketConsumer> getReceivePacketConsumers() {
         return Collections.unmodifiableList(receivePacketConsumers);
     }
@@ -144,7 +150,7 @@ public final class ConnectionManager {
      *
      * @param packetConsumer the packet consumer
      */
-    public void onPacketReceive(PacketConsumer packetConsumer) {
+    public void onPacketReceive(@NotNull PacketConsumer packetConsumer) {
         this.receivePacketConsumers.add(packetConsumer);
     }
 
@@ -153,10 +159,11 @@ public final class ConnectionManager {
      * <p>
      * Shouldn't be override if already defined.
      *
-     * @param uuidProvider the new player connection uuid provider
+     * @param uuidProvider the new player connection uuid provider,
+     *                     setting it to null would apply a random UUID for each player connection
      * @see #getPlayerConnectionUuid(PlayerConnection, String)
      */
-    public void setUuidProvider(UuidProvider uuidProvider) {
+    public void setUuidProvider(@Nullable UuidProvider uuidProvider) {
         this.uuidProvider = uuidProvider;
     }
 
@@ -166,10 +173,12 @@ public final class ConnectionManager {
      * to give the player the right {@link UUID}.
      *
      * @param playerConnection the player connection
+     * @param username         the username given by the connection
      * @return the uuid based on {@code playerConnection}
      * return a random UUID if no UUID provider is defined see {@link #setUuidProvider(UuidProvider)}
      */
-    public UUID getPlayerConnectionUuid(PlayerConnection playerConnection, String username) {
+    @NotNull
+    public UUID getPlayerConnectionUuid(@NotNull PlayerConnection playerConnection, @NotNull String username) {
         if (uuidProvider == null)
             return UUID.randomUUID();
         return uuidProvider.provide(playerConnection, username);
@@ -180,7 +189,7 @@ public final class ConnectionManager {
      *
      * @param playerProvider the new {@link PlayerProvider}, can be set to null to apply the default provider
      */
-    public void setPlayerProvider(PlayerProvider playerProvider) {
+    public void setPlayerProvider(@Nullable PlayerProvider playerProvider) {
         this.playerProvider = playerProvider;
     }
 
@@ -189,6 +198,7 @@ public final class ConnectionManager {
      *
      * @return the current {@link PlayerProvider}
      */
+    @NotNull
     public PlayerProvider getPlayerProvider() {
         return playerProvider == null ? playerProvider = Player::new : playerProvider;
     }
@@ -198,6 +208,7 @@ public final class ConnectionManager {
      *
      * @return an unmodifiable list containing all the {@link Player} initialization consumer
      */
+    @NotNull
     public List<Consumer<Player>> getPlayerInitializations() {
         return Collections.unmodifiableList(playerInitializations);
     }
@@ -208,7 +219,7 @@ public final class ConnectionManager {
      *
      * @param playerInitialization the {@link Player} initialization consumer
      */
-    public void addPlayerInitialization(Consumer<Player> playerInitialization) {
+    public void addPlayerInitialization(@NotNull Consumer<Player> playerInitialization) {
         this.playerInitializations.add(playerInitialization);
     }
 
@@ -220,7 +231,7 @@ public final class ConnectionManager {
      *
      * @param player the player to add
      */
-    public void createPlayer(Player player) {
+    public void createPlayer(@NotNull Player player) {
         this.players.add(player);
         this.connectionPlayerMap.put(player.getPlayerConnection(), player);
     }
@@ -232,7 +243,7 @@ public final class ConnectionManager {
      * @param username   the new player username
      * @param connection the new player connection
      */
-    public void createPlayer(UUID uuid, String username, PlayerConnection connection) {
+    public void createPlayer(@NotNull UUID uuid, @NotNull String username, @NotNull PlayerConnection connection) {
         final Player player = getPlayerProvider().createPlayer(uuid, username, connection);
         createPlayer(player);
     }
@@ -244,7 +255,7 @@ public final class ConnectionManager {
      *
      * @param connection the player connection
      */
-    public void removePlayer(PlayerConnection connection) {
+    public void removePlayer(@NotNull PlayerConnection connection) {
         final Player player = this.connectionPlayerMap.get(connection);
         if (player == null)
             return;