Added PMD Plugin and changed isBedrockPlayer to isFloodgatePlayer

api/src/main/java/org/geysermc/floodgate/api/FloodgateApi.java

@@ -36,7 +36,7 @@ public interface FloodgateApi {
      * Returns the Floodgate API instance.
      */
     static FloodgateApi getInstance() {
-        return InstanceHolder.getInstance();
+        return InstanceHolder.getApi();
     }
 
     /**
@@ -45,7 +45,7 @@ public interface FloodgateApi {
      * @param uuid The uuid of the <b>online</b> player
      * @return true if the given <b>online</b> player is a Bedrock player
      */
-    boolean isBedrockPlayer(UUID uuid);
+    boolean isFloodgatePlayer(UUID uuid);
 
     /**
      * Get info about the given Bedrock player
@@ -66,7 +66,7 @@ public interface FloodgateApi {
     /**
      * Checks if the uuid of the player has the {@link #createJavaPlayerId(long)} format. This
      * method can't validate a linked player uuid, since that doesn't equal the format. Use {@link
-     * #isBedrockPlayer(UUID)} if you want to include linked accounts.
+     * #isFloodgatePlayer(UUID)} if you want to include linked accounts.
      *
      * @param uuid the uuid to check
      * @return true if the given uuid has the correct format.

api/src/main/java/org/geysermc/floodgate/api/InstanceHolder.java

@@ -32,25 +32,28 @@ import org.geysermc.floodgate.api.inject.PlatformInjector;
 import org.geysermc.floodgate.api.link.PlayerLink;
 
 public final class InstanceHolder {
-    @Getter private static FloodgateApi instance;
+    @Getter private static FloodgateApi api;
     @Getter private static PlayerLink playerLink;
     @Getter private static PlatformInjector injector;
     @Getter private static HandshakeHandlers handshakeHandlers;
-    private static UUID key;
+    private static UUID storedKey;
 
-    public static boolean setInstance(
+    public static boolean set(
             FloodgateApi floodgateApi,
             PlayerLink link,
             PlatformInjector platformInjector,
             HandshakeHandlers handshakeHandlers,
-            UUID key
+            UUID key) {
-    ) {
+
-        if (instance == null) {
+        if (storedKey != null) {
-            InstanceHolder.key = key;
+            if (!storedKey.equals(key)) {
-        } else if (!InstanceHolder.key.equals(key)) {
                 return false;
             }
-        instance = floodgateApi;
+        } else {
+            storedKey = key;
+        }
+
+        api = floodgateApi;
         playerLink = link;
         injector = platformInjector;
         InstanceHolder.handshakeHandlers = handshakeHandlers;
@@ -59,6 +62,6 @@ public final class InstanceHolder {
 
     @SuppressWarnings("unchecked")
     public static <T extends FloodgateApi> T castApi(Class<T> cast) {
-        return (T) instance;
+        return (T) api;
     }
 }

api/src/main/java/org/geysermc/floodgate/api/link/PlayerLink.java

@@ -27,6 +27,7 @@ package org.geysermc.floodgate.api.link;
 
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.geysermc.floodgate.util.LinkedPlayer;
 
 /**
@@ -49,7 +50,8 @@ public interface PlayerLink {
      * @return a completable future with the {@link LinkedPlayer}. The future will have a null value
      * if that Bedrock player isn't linked
      */
-    CompletableFuture<LinkedPlayer> getLinkedPlayer(UUID bedrockId);
+    @NonNull
+    CompletableFuture<LinkedPlayer> getLinkedPlayer(@NonNull UUID bedrockId);
 
     /**
      * Tells if the given player is a linked player
@@ -57,7 +59,8 @@ public interface PlayerLink {
      * @param playerId the uuid of the player to check, can be both a Java or a Bedrock uuid
      * @return true if the player is a linked player
      */
-    CompletableFuture<Boolean> isLinkedPlayer(UUID playerId);
+    @NonNull
+    CompletableFuture<Boolean> isLinkedPlayer(@NonNull UUID playerId);
 
     /**
      * Links a Java account to a Bedrock account.
@@ -67,7 +70,11 @@ public interface PlayerLink {
      * @param username  the username of the Java player
      * @return a future holding void on success or completed exceptionally when failed
      */
-    CompletableFuture<Void> linkPlayer(UUID bedrockId, UUID javaId, String username);
+    @NonNull
+    CompletableFuture<Void> linkPlayer(
+            @NonNull UUID bedrockId,
+            @NonNull UUID javaId,
+            @NonNull String username);
 
     /**
      * Unlinks a Java account from a Bedrock account.
@@ -75,7 +82,8 @@ public interface PlayerLink {
      * @param javaId the uuid of the Java player
      * @return a future holding void on success or completed exceptionally when failed
      */
-    CompletableFuture<Void> unlinkPlayer(UUID javaId);
+    @NonNull
+    CompletableFuture<Void> unlinkPlayer(@NonNull UUID javaId);
 
     /**
      * Creates a link request for the given Java player.
@@ -86,10 +94,11 @@ public interface PlayerLink {
      * @return a future holding the result of the link request which will be a {@link
      * LinkRequestResult} on failure and the link code (string) on success
      */
+    @NonNull
     CompletableFuture<?> createLinkRequest(
-            UUID javaId,
+            @NonNull UUID javaId,
-            String javaUsername,
+            @NonNull String javaUsername,
-            String bedrockUsername
+            @NonNull String bedrockUsername
     );
 
     /**
@@ -101,11 +110,12 @@ public interface PlayerLink {
      * @param code            the code created in {@link #createLinkRequest(UUID, String, String)}
      * @return a future holding the result of the link verification
      */
+    @NonNull
     CompletableFuture<LinkRequestResult> verifyLinkRequest(
-            UUID bedrockId,
+            @NonNull UUID bedrockId,
-            String javaUsername,
+            @NonNull String javaUsername,
-            String bedrockUsername,
+            @NonNull String bedrockUsername,
-            String code
+            @NonNull String code
     );
 
     /**

api/src/main/java/org/geysermc/floodgate/api/player/PropertyKey.java

@@ -51,18 +51,6 @@ public class PropertyKey {
         this.removable = removable;
     }
 
-    @Override
-    public boolean equals(Object obj) {
-        if (obj instanceof PropertyKey) {
-            return key.equals(((PropertyKey) obj).key);
-        }
-
-        if (obj instanceof String) {
-            return key.equals(obj);
-        }
-        return false;
-    }
-
     public Result isAddAllowed(Object obj) { //todo use for add and remove
         if (obj instanceof PropertyKey) {
             PropertyKey propertyKey = (PropertyKey) obj;

bungee/src/main/java/org/geysermc/floodgate/handler/BungeeDataHandler.java

@@ -106,16 +106,19 @@ public final class BungeeDataHandler {
                 return;
             }
 
-            switch (result.getResultType()) {
+            if (result.getResultType() == ResultType.EXCEPTION) {
-                case EXCEPTION:
                 event.setCancelReason(config.getDisconnect().getInvalidKey());
-                    break;
+                event.completeIntent(plugin);
-                case INVALID_DATA_LENGTH:
+                return;
+            }
+
+            if (result.getResultType() == ResultType.INVALID_DATA_LENGTH) {
                 event.setCancelReason(TextComponent.fromLegacyText(String.format(
                         config.getDisconnect().getInvalidArgumentsLength(),
                         BedrockData.EXPECTED_LENGTH, result.getBedrockData().getDataLength()
                 )));
-                    break;
+                event.completeIntent(plugin);
+                return;
             }
 
             // only continue when SUCCESS
@@ -155,7 +158,7 @@ public final class BungeeDataHandler {
 
     public void handleServerConnect(ProxiedPlayer player) {
         // Passes the information through to the connecting server if enabled
-        if (config.isSendFloodgateData() && api.isBedrockPlayer(player.getUniqueId())) {
+        if (config.isSendFloodgateData() && api.isFloodgatePlayer(player.getUniqueId())) {
             Handshake handshake = ReflectionUtils.getCastedValue(
                     player.getPendingConnection(), CACHED_HANDSHAKE_PACKET
             );

bungee/src/main/java/org/geysermc/floodgate/pluginmessage/BungeePluginMessageHandler.java

@@ -25,7 +25,9 @@
 
 package org.geysermc.floodgate.pluginmessage;
 
+import com.google.gson.JsonIOException;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonSyntaxException;
 import com.google.inject.Inject;
 import com.google.inject.name.Named;
 import java.io.ByteArrayInputStream;
@@ -165,7 +167,7 @@ public final class BungeePluginMessageHandler extends PluginMessageHandler imple
                 try {
                     Reader reader = new InputStreamReader(new ByteArrayInputStream(responseData));
                     response = GSON.fromJson(reader, JsonObject.class);
-                } catch (Throwable throwable) {
+                } catch (JsonIOException | JsonSyntaxException throwable) {
                     logger.error("Failed to read Skin response", throwable);
                     return;
                 }

bungee/src/main/java/org/geysermc/floodgate/util/BungeeCommandUtil.java

@@ -116,14 +116,14 @@ public final class BungeeCommandUtil implements CommandUtil {
                 break;
             case ONLY_JAVA:
                 for (ProxiedPlayer player : players) {
-                    if (!api.isBedrockPlayer(player.getUniqueId())) {
+                    if (!api.isFloodgatePlayer(player.getUniqueId())) {
                         usernames.add(player.getName());
                     }
                 }
                 break;
             case ONLY_BEDROCK:
                 for (ProxiedPlayer player : players) {
-                    if (api.isBedrockPlayer(player.getUniqueId())) {
+                    if (api.isFloodgatePlayer(player.getUniqueId())) {
                         usernames.add(player.getName());
                     }
                 }

common/src/main/java/org/geysermc/floodgate/FloodgatePlatform.java

@@ -29,6 +29,7 @@ import com.google.inject.Inject;
 import com.google.inject.Injector;
 import com.google.inject.Module;
 import com.google.inject.name.Named;
+import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.UUID;
@@ -56,8 +57,12 @@ public class FloodgatePlatform {
     private Injector guice;
 
     @Inject
-    public FloodgatePlatform(FloodgateApi api, PlatformInjector platformInjector,
+    public FloodgatePlatform(
-                             FloodgateLogger logger, Injector guice) {
+            FloodgateApi api,
+            PlatformInjector platformInjector,
+            FloodgateLogger logger,
+            Injector guice) {
+
         this.api = api;
         this.injector = platformInjector;
         this.logger = logger;
@@ -69,15 +74,14 @@ public class FloodgatePlatform {
             @Named("dataDirectory") Path dataDirectory,
             ConfigLoader configLoader,
             FloodgateConfigHolder configHolder,
-            HandshakeHandlers handshakeHandlers
+            HandshakeHandlers handshakeHandlers) {
-    ) {
 
         if (!Files.isDirectory(dataDirectory)) {
             try {
                 Files.createDirectory(dataDirectory);
-            } catch (Exception exception) {
+            } catch (IOException exception) {
                 logger.error("Failed to create the data folder", exception);
-                throw new RuntimeException("Failed to create the data folder");
+                throw new RuntimeException("Failed to create the data folder", exception);
             }
         }
 
@@ -90,7 +94,7 @@ public class FloodgatePlatform {
         guice = guice.createChildInjector(new ConfigLoadedModule(config));
         PlayerLink link = guice.getInstance(PlayerLinkLoader.class).load();
 
-        InstanceHolder.setInstance(api, link, this.injector, handshakeHandlers, KEY);
+        InstanceHolder.set(api, link, this.injector, handshakeHandlers, KEY);
     }
 
     public boolean enable(Module... postInitializeModules) {

common/src/main/java/org/geysermc/floodgate/addon/addonmanager/AddonManagerHandler.java

@@ -31,6 +31,7 @@ import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.MessageToByteEncoder;
 import lombok.RequiredArgsConstructor;
 import org.geysermc.floodgate.inject.CommonPlatformInjector;
+import org.geysermc.floodgate.util.Constants;
 
 @RequiredArgsConstructor
 public final class AddonManagerHandler extends MessageToByteEncoder<ByteBuf> {
@@ -57,8 +58,7 @@ public final class AddonManagerHandler extends MessageToByteEncoder<ByteBuf> {
         }
 
         int index = msg.readerIndex();
-        // LoginSuccess packet = 2
+        if (readVarInt(msg) == Constants.LOGIN_SUCCESS_PACKET_ID) {
-        if (readVarInt(msg) == 2) {
             loggedIn = true;
             injector.loginSuccessCall(channel);
         }

common/src/main/java/org/geysermc/floodgate/api/SimpleFloodgateApi.java

@@ -43,7 +43,7 @@ public class SimpleFloodgateApi implements FloodgateApi {
     private final PluginMessageHandler pluginMessageHandler;
 
     @Override
-    public boolean isBedrockPlayer(UUID uuid) {
+    public boolean isFloodgatePlayer(UUID uuid) {
         return getPlayer(uuid) != null;
     }
 

common/src/main/java/org/geysermc/floodgate/command/LinkAccountCommand.java

@@ -35,6 +35,7 @@ import cloud.commandframework.context.CommandContext;
 import com.google.inject.Inject;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
+import net.kyori.adventure.text.Component;
 import org.geysermc.floodgate.api.FloodgateApi;
 import org.geysermc.floodgate.api.link.LinkRequestResult;
 import org.geysermc.floodgate.api.link.PlayerLink;
@@ -74,7 +75,7 @@ public final class LinkAccountCommand implements FloodgateCommand {
         }
 
         // when the player is a Bedrock player
-        if (api.isBedrockPlayer(sender.uuid())) {
+        if (api.isFloodgatePlayer(sender.uuid())) {
             if (!context.contains("code")) {
                 sender.sendMessage(Message.BEDROCK_USAGE);
                 return;
@@ -107,6 +108,9 @@ public final class LinkAccountCommand implements FloodgateCommand {
                             case LINK_COMPLETED:
                                 sender.disconnect(Message.LINK_REQUEST_COMPLETED, targetName);
                                 break;
+                            default:
+                                sender.disconnect(Component.text("Invalid account linking result"));
+                                break;
                         }
                     });
             return;

common/src/main/java/org/geysermc/floodgate/config/FloodgateConfig.java

@@ -47,7 +47,7 @@ public class FloodgateConfig {
     private boolean debug;
     private int configVersion;
 
-    private Key key = null;
+    private Key key;
 
     public void setKey(Key key) {
         if (this.key == null) {

common/src/main/java/org/geysermc/floodgate/config/loader/ConfigInitializer.java

@@ -43,8 +43,8 @@ public class ConfigInitializer {
     private static final Yaml YAML;
 
     static {
-        Constructor constructor = new CustomClassLoaderConstructor(
+        Constructor constructor =
-                ConfigInitializer.class.getClassLoader());
+                new CustomClassLoaderConstructor(ConfigInitializer.class.getClassLoader());
 
         constructor.setPropertyUtils(new PropertyUtils() {
             @Override
@@ -54,8 +54,11 @@ public class ConfigInitializer {
                 return properties;
             }
 
-            private void getPropertiesFromClass(Class<?> type, Class<?> stopAfter,
+            private void getPropertiesFromClass(
+                    Class<?> type,
+                    Class<?> stopAfter,
                     Map<String, Property> propertyMap) {
+
                 Class<?> current = type;
                 while (!Object.class.equals(current)) {
                     for (Field field : current.getDeclaredFields()) {
@@ -98,7 +101,8 @@ public class ConfigInitializer {
         YAML = new Yaml(constructor);
     }
 
-    public static <T extends FloodgateConfig> T initializeFrom(InputStream dataStream,
+    public static <T extends FloodgateConfig> T initializeFrom(
+            InputStream dataStream,
             Class<T> configClass) {
         return YAML.loadAs(dataStream, configClass);
     }

common/src/main/java/org/geysermc/floodgate/config/loader/ConfigLoader.java

@@ -86,7 +86,8 @@ public final class ConfigLoader {
             }
         } catch (Exception exception) {
             logger.error("Error while loading config", exception);
-            throw new RuntimeException("Failed to load the config! Try to delete the config file");
+            throw new RuntimeException(
+                    "Failed to load the config! Try to delete the config file", exception);
         }
 
         Path keyPath = dataFolder.resolve(configInstance.getKeyFileName());
@@ -125,7 +126,7 @@ public final class ConfigLoader {
             configInstance.setKey(key);
         } catch (IOException exception) {
             logger.error("Error while reading the key", exception);
-            throw new RuntimeException("Failed to read the key!");
+            throw new RuntimeException("Failed to read the key!", exception);
         }
 
         return configInstance;

common/src/main/java/org/geysermc/floodgate/config/updater/ConfigFileUpdater.java

@@ -51,9 +51,13 @@ public final class ConfigFileUpdater {
      * @param defaultConfigLocation the location of the default Floodgate config
      * @throws IOException if an I/O error occurs
      */
-    public void update(Path configLocation, Map<String, Object> currentVersion,
+    public void update(
-                       Map<String, String> renames, String defaultConfigLocation)
+            Path configLocation,
+            Map<String, Object> currentVersion,
+            Map<String, String> renames,
+            String defaultConfigLocation)
             throws IOException {
+
         List<String> notFound = new ArrayList<>();
         List<String> newConfig = defaultConfigHandler.loadDefaultConfig(defaultConfigLocation);
 
@@ -64,7 +68,7 @@ public final class ConfigFileUpdater {
         for (int i = 0; i < newConfig.size(); i++) {
             line = newConfig.get(i);
             // we don't have to check comments or empty lines
-            if (line.length() == 0 || line.startsWith("#")) {
+            if (line.isEmpty() || line.charAt(0) == '#') {
                 continue;
             }
 
@@ -74,7 +78,7 @@ public final class ConfigFileUpdater {
             }
 
             // end of subcategory
-            if (spaces.length() > 0 && currentSpaces.length() < spaces.length()) {
+            if (!spaces.isEmpty() && currentSpaces.length() < spaces.length()) {
                 // we can assume this since we don't allow subcategories of subcategories
                 spaces = "";
                 map = null;
@@ -134,7 +138,7 @@ public final class ConfigFileUpdater {
         logger.info("Successfully updated the config file! " +
                 "Your old config has been moved to config-old.yml");
 
-        if (notFound.size() > 0) {
+        if (!notFound.isEmpty()) {
             StringBuilder messageBuilder = new StringBuilder(
                     "Please note that the following keys we not found in the old config and " +
                             "are now using the default Floodgate config value. Missing/new keys: ");

common/src/main/java/org/geysermc/floodgate/config/updater/ConfigUpdater.java

@@ -48,16 +48,15 @@ public final class ConfigUpdater {
     public void update(String defaultConfigLocation) {
         Path configLocation = dataFolder.resolve("config.yml");
 
-        BufferedReader configReader;
+        Map<String, Object> config;
-        try {
+
-            configReader = Files.newBufferedReader(configLocation);
+        try (BufferedReader configReader = Files.newBufferedReader(configLocation)) {
+            config = new Yaml().load(configReader);
         } catch (IOException exception) {
             logger.error("Error while opening the config file", exception);
-            throw new RuntimeException("Failed to update config");
+            throw new RuntimeException("Failed to update config", exception);
         }
 
-        Map<String, Object> config = new Yaml().load(configReader);
-
         // new name -> old name
         Map<String, String> renames = new HashMap<>();
 
@@ -93,7 +92,7 @@ public final class ConfigUpdater {
             fileUpdater.update(configLocation, config, renames, defaultConfigLocation);
         } catch (IOException exception) {
             logger.error("Error while updating the config file", exception);
-            throw new RuntimeException("Failed to update config");
+            throw new RuntimeException("Failed to update config", exception);
         }
     }
 }

common/src/main/java/org/geysermc/floodgate/link/DisabledPlayerLink.java

@@ -42,6 +42,8 @@ final class DisabledPlayerLink implements PlayerLink {
     public void load() {
     }
 
+    //todo don't return null
+
     @Override
     public CompletableFuture<LinkedPlayer> getLinkedPlayer(UUID bedrockId) {
         return null;

common/src/main/java/org/geysermc/floodgate/link/GlobalPlayerLinking.java

@@ -99,7 +99,7 @@ public class GlobalPlayerLinking extends CommonPlayerLink {
     // player linking and unlinking now goes through the global player linking server.
     // so individual servers can't register nor unlink players.
 
-    //todo probably return a failed future instead of returning null?
+    //todo don't return null
 
     @Override
     public CompletableFuture<Void> linkPlayer(UUID bedrockId, UUID javaId, String username) {

common/src/main/java/org/geysermc/floodgate/link/LinkRequestImpl.java

@@ -47,6 +47,7 @@ public final class LinkRequestImpl implements LinkRequest {
         requestTime = Instant.now().getEpochSecond();
     }
 
+    @Override
     public boolean isExpired(long linkTimeout) {
         long timePassed = Instant.now().getEpochSecond() - requestTime;
         return timePassed > linkTimeout;

common/src/main/java/org/geysermc/floodgate/link/PlayerLinkLoader.java

@@ -40,6 +40,7 @@ import java.net.URLClassLoader;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;
+import java.util.Locale;
 import java.util.stream.Collectors;
 import javax.inject.Named;
 import org.geysermc.floodgate.api.link.PlayerLink;
@@ -61,13 +62,13 @@ public final class PlayerLinkLoader {
             throw new IllegalStateException("Config cannot be null!");
         }
 
-        FloodgateConfig.PlayerLinkConfig linkConfig = config.getPlayerLink();
+        FloodgateConfig.PlayerLinkConfig linkingConfig = config.getPlayerLink();
-        if (!linkConfig.isEnabled()) {
+        if (!linkingConfig.isEnabled()) {
             return new DisabledPlayerLink();
         }
 
         // we use our own internal PlayerLinking when global linking is enabled
-        if (linkConfig.isUseGlobalLinking()) {
+        if (linkingConfig.isUseGlobalLinking()) {
             return injector.getInstance(GlobalPlayerLinking.class);
         }
 
@@ -81,7 +82,7 @@ public final class PlayerLinkLoader {
             return null;
         }
 
-        if (files.size() == 0) {
+        if (files.isEmpty()) {
             logger.error("Failed to find a database implementation");
             return null;
         }
@@ -89,17 +90,20 @@ public final class PlayerLinkLoader {
         Path implementationPath = files.get(0);
 
         // We only want to load one database implementation
-        String type = linkConfig.getType().toLowerCase();
         if (files.size() > 1) {
-            implementationPath = null;
+            boolean found = false;
+
+            String type = linkingConfig.getType().toLowerCase(Locale.ROOT);
             for (Path path : files) {
-                if (path.getFileName().toString().toLowerCase().contains(type)) {
+                if (path.getFileName().toString().toLowerCase(Locale.ROOT).contains(type)) {
                     implementationPath = path;
+                    found = true;
                 }
             }
-            if (implementationPath == null) {
+
+            if (!found) {
                 logger.error("Failed to find an implementation for type: {}",
-                        linkConfig.getType());
+                        linkingConfig.getType());
                 return null;
             }
         }
@@ -107,23 +111,29 @@ public final class PlayerLinkLoader {
         Class<? extends PlayerLink> mainClass;
         try {
             URL pluginUrl = implementationPath.toUri().toURL();
-            URLClassLoader classLoader = new URLClassLoader(
+
-                    new URL[]{pluginUrl},
+            try (URLClassLoader classLoader = new URLClassLoader(
-                    PlayerLinkLoader.class.getClassLoader()
+                    new URL[]{pluginUrl}, PlayerLinkLoader.class.getClassLoader())) {
+
+                String mainClassName;
+
+                try (InputStream linkConfigStream =
+                             classLoader.getResourceAsStream("config.json")) {
+
+                    requireNonNull(linkConfigStream, "Implementation should have a config");
+
+                    JsonObject linkConfig = new Gson().fromJson(
+                            new InputStreamReader(linkConfigStream), JsonObject.class
                     );
 
-            InputStream linkImplConfigStream = classLoader.getResourceAsStream("config.json");
+                    mainClassName = linkConfig.get("mainClass").getAsString();
-            requireNonNull(linkImplConfigStream, "Database implementation should contain a config");
+                }
 
-            JsonObject linkImplConfig = new Gson().fromJson(
-                    new InputStreamReader(linkImplConfigStream), JsonObject.class
-            );
-
-            String mainClassName = linkImplConfig.get("mainClass").getAsString();
                 mainClass = (Class<? extends PlayerLink>) classLoader.loadClass(mainClassName);
+            }
         } catch (ClassCastException exception) {
             logger.error("The database implementation ({}) doesn't extend the PlayerLink class!",
-                    implementationPath.getFileName().toString());
+                    implementationPath.getFileName().toString(), exception);
             return null;
         } catch (Exception exception) {
             logger.error("Error while loading database jar", exception);

common/src/main/java/org/geysermc/floodgate/logger/JavaUtilFloodgateLogger.java

@@ -37,7 +37,7 @@ import org.geysermc.floodgate.util.LanguageManager;
 public final class JavaUtilFloodgateLogger implements FloodgateLogger {
     private final Logger logger;
     private final LanguageManager languageManager;
-    private Level originLevel = null;
+    private Level originLevel;
 
     @Override
     public void error(String message, Object... args) {

common/src/main/java/org/geysermc/floodgate/platform/command/CommandMessage.java

@@ -51,7 +51,7 @@ public interface CommandMessage {
         StringBuilder builder = new StringBuilder();
         for (int i = 0; i < translateParts.length; i++) {
             builder.append(manager.getString(translateParts[i], locale, args));
-            if (++i != translateParts.length) {
+            if (translateParts.length != i + 1) {
                 builder.append(" ");
             }
         }

common/src/main/java/org/geysermc/floodgate/platform/pluginmessage/PluginMessageHandler.java

@@ -53,7 +53,7 @@ public abstract class PluginMessageHandler {
     }
 
     public void sendSkinResponse(UUID player, boolean failed, String response) {
-        return; // Proxy implementations don't send responses
+        // Proxy implementations don't send responses
     }
 
     protected byte[] createFormData(Form form) {

common/src/main/java/org/geysermc/floodgate/player/FloodgatePlayerImpl.java

@@ -154,10 +154,12 @@ public final class FloodgatePlayerImpl implements FloodgatePlayer {
                 CompletableFuture.completedFuture(null);
     }
 
+    @Override
     public UUID getCorrectUniqueId() {
         return linkedPlayer != null ? linkedPlayer.getJavaUniqueId() : javaUniqueId;
     }
 
+    @Override
     public String getCorrectUsername() {
         return linkedPlayer != null ? linkedPlayer.getJavaUsername() : javaUsername;
     }

common/src/main/java/org/geysermc/floodgate/player/HandshakeHandler.java

@@ -64,9 +64,8 @@ public final class HandshakeHandler {
     private final AttributeKey<FloodgatePlayer> playerAttribute;
     private final FloodgateLogger logger;
 
-    public HandshakeResult handle(Channel channel, @NonNull String hostname) {
+    public HandshakeResult handle(Channel channel, @NonNull String originalHostname) {
-        try {
+        String[] split = originalHostname.split("\0");
-            String[] split = hostname.split("\0");
         String data = null;
 
         StringBuilder hostnameBuilder = new StringBuilder();
@@ -78,7 +77,7 @@ public final class HandshakeHandler {
             hostnameBuilder.append(value);
         }
         // hostname now doesn't have Floodgate data anymore if it had
-            hostname = hostnameBuilder.toString();
+        String hostname = hostnameBuilder.toString();
 
         if (data == null) {
             return callHandlerAndReturnResult(
@@ -91,6 +90,7 @@ public final class HandshakeHandler {
                 Base64Utils.getEncodedLength(AesCipher.IV_LENGTH);
         int lastSplitIndex = data.lastIndexOf(0x21);
 
+        try {
             byte[] floodgateData;
             byte[] rawSkinData = null;
 
@@ -181,8 +181,8 @@ public final class HandshakeHandler {
             ResultType resultType,
             Channel channel,
             BedrockData bedrockData,
-            String hostname
+            String hostname) {
-    ) {
+
         HandshakeData handshakeData = new HandshakeDataImpl(channel, bedrockData != null,
                 bedrockData, null, null, hostname, null);
         handshakeHandlers.callHandshakeHandlers(handshakeData);

common/src/main/java/org/geysermc/floodgate/player/UserAudience.java

@@ -46,6 +46,7 @@ public interface UserAudience extends Identified, Identity, Audience {
 
     boolean hasPermission(@NonNull final String permission);
 
+    @Override
     void sendMessage(final @NonNull Identity source,
                      final @NonNull Component message,
                      final @NonNull MessageType type);

common/src/main/java/org/geysermc/floodgate/player/UserAudienceArgument.java

@@ -31,6 +31,7 @@ import cloud.commandframework.arguments.parser.ArgumentParser;
 import cloud.commandframework.context.CommandContext;
 import com.google.common.collect.ImmutableList;
 import java.util.List;
+import java.util.Locale;
 import java.util.Queue;
 import java.util.UUID;
 import lombok.RequiredArgsConstructor;
@@ -154,13 +155,18 @@ public final class UserAudienceArgument extends CommandArgument<UserAudience, Us
                 final @NonNull CommandContext<UserAudience> commandContext,
                 final @NonNull String input
         ) {
-            CommandUtil commandUtil = commandContext.get("CommandUtil");
+            final CommandUtil commandUtil = commandContext.get("CommandUtil");
+            final String trimmedInput = input.trim();
 
-            final String lowercaseInput = input.toLowerCase().trim();
+            if (trimmedInput.isEmpty()) {
+                return ImmutableList.copyOf(commandUtil.getOnlineUsernames(limitTo));
+            }
+
+            final String lowercaseInput = input.toLowerCase(Locale.ROOT);
             final ImmutableList.Builder<String> builder = ImmutableList.builder();
 
             for (final String player : commandUtil.getOnlineUsernames(limitTo)) {
-                if (lowercaseInput.isEmpty() || player.toLowerCase().startsWith(lowercaseInput)) {
+                if (player.toLowerCase(Locale.ROOT).startsWith(lowercaseInput)) {
                     builder.add(player);
                 }
             }
@@ -182,7 +188,7 @@ public final class UserAudienceArgument extends CommandArgument<UserAudience, Us
         }
 
         @Override
-        public synchronized @NonNull Throwable fillInStackTrace() {
+        public @NonNull Throwable fillInStackTrace() {
             return this;
         }
     }

common/src/main/java/org/geysermc/floodgate/skin/SkinUploader.java

@@ -27,6 +27,7 @@ package org.geysermc.floodgate.skin;
 
 import com.google.gson.JsonObject;
 import java.awt.image.BufferedImage;
+import java.util.Locale;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
@@ -43,7 +44,7 @@ public final class SkinUploader {
     private static final int MAX_TRIES = 3;
 
     private final Executor requestExecutor = Executors.newSingleThreadExecutor();
-    private long nextResult = 0;
+    private long nextResult;
 
     public CompletableFuture<UploadResult> uploadSkin(@Nonnull RawSkin rawSkin) {
         return CompletableFuture.supplyAsync(() -> uploadSkinInner(rawSkin, 0), requestExecutor);
@@ -65,12 +66,11 @@ public final class SkinUploader {
 
         try {
             UploadResult result = parseAndHandleResponse(HttpUtils.post(url, image));
-            if (result.httpCode == 429) {
+            if (result.getHttpCode() == 429) {
-                times += 1;
+                if (times + 1 >= MAX_TRIES) {
-                if (times >= MAX_TRIES) {
                     return result;
                 }
-                uploadSkinInner(rawSkin, times);
+                uploadSkinInner(rawSkin, times + 1);
             }
             return result;
         } catch (RuntimeException exception) {
@@ -79,7 +79,7 @@ public final class SkinUploader {
     }
 
     private String getUploadUrlParameters(SkinModel model) {
-        return "?visibility=1&model=" + model.name;
+        return "?visibility=1&model=" + model.getName();
     }
 
     private UploadResult parseAndHandleResponse(HttpResponse response) {
@@ -103,14 +103,15 @@ public final class SkinUploader {
         STEVE, ALEX;
 
         public static final SkinModel[] VALUES = values();
-        private final String name = name().toLowerCase();
+
+        @Getter private final String name = name().toLowerCase(Locale.ROOT);
 
         public static SkinModel getByOrdinal(int ordinal) {
             return VALUES.length > ordinal ? VALUES[ordinal] : STEVE;
         }
 
         public static SkinModel getByName(String name) {
-            return name == null || !name.equalsIgnoreCase("alex") ? STEVE : ALEX;
+            return "alex".equalsIgnoreCase(name) ? ALEX : STEVE;
         }
     }
 

common/src/main/java/org/geysermc/floodgate/util/Constants.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2019-2021 GeyserMC. http://geysermc.org
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @author GeyserMC
+ * @link https://github.com/GeyserMC/Floodgate
+ */
+
+package org.geysermc.floodgate.util;
+
+public final class Constants {
+    public static final int LOGIN_SUCCESS_PACKET_ID = 2;
+}

common/src/main/java/org/geysermc/floodgate/util/LanguageManager.java

@@ -28,6 +28,7 @@ package org.geysermc.floodgate.util;
 import com.google.common.base.Joiner;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.io.Reader;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
 import java.text.MessageFormat;
@@ -63,8 +64,8 @@ public final class LanguageManager {
      */
     private static String formatLocale(String locale) {
         try {
-            String[] parts = locale.toLowerCase().split("_");
+            String[] parts = locale.toLowerCase(Locale.ROOT).split("_");
-            return parts[0] + "_" + parts[1].toUpperCase();
+            return parts[0] + "_" + parts[1].toUpperCase(Locale.ROOT);
         } catch (Exception e) {
             return locale;
         }
@@ -117,31 +118,32 @@ public final class LanguageManager {
      * @return true if the locale has been found
      */
     public boolean loadLocale(String locale) {
-        locale = formatLocale(locale);
+        String formatLocale = formatLocale(locale);
 
         // just return if the locale has been loaded already
-        if (localeMappings.containsKey(locale)) {
+        if (localeMappings.containsKey(formatLocale)) {
             return true;
         }
 
         InputStream localeStream = LanguageManager.class.getClassLoader().getResourceAsStream(
-                "languages/texts/" + locale + ".properties");
+                "languages/texts/" + formatLocale + ".properties");
 
         // load the locale
         if (localeStream != null) {
             Properties localeProp = new Properties();
-            try {
+
-                localeProp.load(new InputStreamReader(localeStream, StandardCharsets.UTF_8));
+            try (Reader reader = new InputStreamReader(localeStream, StandardCharsets.UTF_8)) {
+                localeProp.load(reader);
             } catch (Exception e) {
                 throw new AssertionError("Failed to load Floodgate locale", e);
             }
 
             // insert the locale into the mappings
-            localeMappings.put(locale, localeProp);
+            localeMappings.put(formatLocale, localeProp);
             return true;
         }
 
-        logger.warn("Missing locale file: " + locale);
+        logger.warn("Missing locale file: " + formatLocale);
         return false;
     }
 

common/src/main/java/org/geysermc/floodgate/util/MessageFormatter.java

@@ -42,9 +42,8 @@ public final class MessageFormatter {
 
         int previousIndex = -1;
         int currentIndex;
-        StringBuilder stringBuilder = new StringBuilder(
+        StringBuilder stringBuilder =
-                message.length() + getArgsContentLength(args)
+                new StringBuilder(message.length() + getArgsContentLength(args));
-        );
 
         for (String argument : args) {
             currentIndex = message.indexOf(DELIM_STR, previousIndex);

common/src/main/java/org/geysermc/floodgate/util/ReflectionUtils.java

@@ -48,7 +48,7 @@ public final class ReflectionUtils {
      */
     @Getter
     @Setter
-    private static String prefix = null;
+    private static String prefix;
 
     static {
         Field modifiersField = null;
@@ -59,12 +59,12 @@ public final class ReflectionUtils {
             try {
                 Method declaredFields = getMethod(Class.class, "getDeclaredFields0", boolean.class);
                 if (declaredFields == null) {
-                    throw new NoSuchMethodException();
+                    throw new NoSuchMethodException("Cannot find method getDeclaredFields0");
                 }
 
                 Field[] fields = castedInvoke(Field.class, declaredFields, false);
                 if (fields == null) {
-                    throw new Exception();
+                    throw new RuntimeException("The Field class cannot have null fields");
                 }
 
                 for (Field field : fields) {
@@ -79,7 +79,7 @@ public final class ReflectionUtils {
                         System.getProperty("java.version"),
                         System.getProperty("java.vendor"),
                         System.getProperty("java.vendor.url")
-                ));
+                ), exception);
             }
         }
 
@@ -382,6 +382,9 @@ public final class ReflectionUtils {
      */
     @Nullable
     public static Object invoke(Object instance, Method method, Object... arguments) {
+        if (method == null) {
+            return null;
+        }
         makeAccessible(method);
         try {
             return method.invoke(instance, arguments);
@@ -410,11 +413,7 @@ public final class ReflectionUtils {
     @SuppressWarnings("unchecked")
     @Nullable
     public static <T> T castedInvoke(Object instance, Method method, Object... arguments) {
-        try {
         return (T) invoke(instance, method, arguments);
-        } catch (NullPointerException exception) {
-            return null;
-        }
     }
 
     /**
@@ -438,12 +437,7 @@ public final class ReflectionUtils {
      */
     @Nullable
     public static Object invokeStatic(Class<?> clazz, String method) {
-        try {
         return invoke(null, getMethod(clazz, method));
-        } catch (NullPointerException exception) {
-            exception.printStackTrace();
-            return null;
-        }
     }
 
     /**

database/sqlite/src/main/java/org/geysermc/floodgate/database/SqliteDatabase.java

@@ -39,6 +39,7 @@ import java.util.Map;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.geysermc.floodgate.api.link.LinkRequest;
 import org.geysermc.floodgate.api.link.LinkRequestResult;
 import org.geysermc.floodgate.link.CommonPlayerLink;
@@ -59,11 +60,12 @@ public class SqliteDatabase extends CommonPlayerLink {
         try {
             Class.forName("org.sqlite.JDBC");
             connection = DriverManager.getConnection("jdbc:sqlite:" + databasePath.toString());
-            Statement statement = connection.createStatement();
+            try (Statement statement = connection.createStatement()) {
                 statement.setQueryTimeout(30);  // set timeout to 30 sec.
                 statement.executeUpdate(
                         "create table if not exists LinkedPlayers (bedrockId string, javaUniqueId string, javaUsername string)"
                 );
+            }
         } catch (ClassNotFoundException exception) {
             getLogger().error("The required class to load the SQLite database wasn't found");
         } catch (SQLException exception) {
@@ -82,12 +84,12 @@ public class SqliteDatabase extends CommonPlayerLink {
     }
 
     @Override
-    public CompletableFuture<LinkedPlayer> getLinkedPlayer(UUID bedrockId) {
+    @NonNull
+    public CompletableFuture<LinkedPlayer> getLinkedPlayer(@NonNull UUID bedrockId) {
         return CompletableFuture.supplyAsync(() -> {
-            try {
+            try (PreparedStatement query = connection.prepareStatement(
-                PreparedStatement query = connection.prepareStatement(
+                    "select * from LinkedPlayers where bedrockId = ?")) {
-                        "select * from LinkedPlayers where bedrockId = ?"
+
-                );
                 query.setString(1, bedrockId.toString());
                 ResultSet result = query.executeQuery();
                 if (!result.next()) {
@@ -97,7 +99,7 @@ public class SqliteDatabase extends CommonPlayerLink {
                 String javaUsername = result.getString("javaUsername");
                 UUID javaUniqueId = UUID.fromString(result.getString("javaUniqueId"));
                 return LinkedPlayer.of(javaUsername, javaUniqueId, bedrockId);
-            } catch (SQLException | NullPointerException exception) {
+            } catch (SQLException exception) {
                 getLogger().error("Error while getting LinkedPlayer", exception);
                 throw new CompletionException("Error while getting LinkedPlayer", exception);
             }
@@ -105,17 +107,17 @@ public class SqliteDatabase extends CommonPlayerLink {
     }
 
     @Override
-    public CompletableFuture<Boolean> isLinkedPlayer(UUID playerId) {
+    @NonNull
+    public CompletableFuture<Boolean> isLinkedPlayer(@NonNull UUID playerId) {
         return CompletableFuture.supplyAsync(() -> {
-            try {
+            try (PreparedStatement query = connection.prepareStatement(
-                PreparedStatement query = connection.prepareStatement(
+                    "select javaUniqueId from LinkedPlayers where bedrockId = ? or javaUniqueId = ?")) {
-                        "select javaUniqueId from LinkedPlayers where bedrockId = ? or javaUniqueId = ?"
+
-                );
                 query.setString(1, playerId.toString());
                 query.setString(2, playerId.toString());
                 ResultSet result = query.executeQuery();
                 return result.next();
-            } catch (SQLException | NullPointerException exception) {
+            } catch (SQLException exception) {
                 getLogger().error("Error while checking if player is a LinkedPlayer", exception);
                 throw new CompletionException(
                         "Error while checking if player is a LinkedPlayer", exception
@@ -125,38 +127,41 @@ public class SqliteDatabase extends CommonPlayerLink {
     }
 
     @Override
-    public CompletableFuture<Void> linkPlayer(UUID bedrockId, UUID javaId, String username) {
+    @NonNull
+    public CompletableFuture<Void> linkPlayer(
+            @NonNull UUID bedrockId,
+            @NonNull UUID javaId,
+            @NonNull String username) {
         return CompletableFuture.runAsync(
                 () -> linkPlayer0(bedrockId, javaId, username),
                 getExecutorService());
     }
 
     private void linkPlayer0(UUID bedrockId, UUID javaId, String username) {
-        try {
+        try (PreparedStatement query =
-            PreparedStatement query = connection.prepareStatement(
+                     connection.prepareStatement("insert into LinkedPlayers values(?, ?, ?)")) {
-                    "insert into LinkedPlayers values(?, ?, ?)"
+
-            );
             query.setString(1, bedrockId.toString());
             query.setString(2, javaId.toString());
             query.setString(3, username);
             query.executeUpdate();
-        } catch (SQLException | NullPointerException exception) {
+        } catch (SQLException exception) {
             getLogger().error("Error while linking player", exception);
             throw new CompletionException("Error while linking player", exception);
         }
     }
 
     @Override
-    public CompletableFuture<Void> unlinkPlayer(UUID javaId) {
+    @NonNull
+    public CompletableFuture<Void> unlinkPlayer(@NonNull UUID javaId) {
         return CompletableFuture.runAsync(() -> {
-            try {
+            try (PreparedStatement query = connection.prepareStatement(
-                PreparedStatement query = connection.prepareStatement(
+                    "delete from LinkedPlayers where javaUniqueId = ? or bedrockId = ?")) {
-                        "delete from LinkedPlayers where javaUniqueId = ? or bedrockId = ?"
+
-                );
                 query.setString(1, javaId.toString());
                 query.setString(2, javaId.toString());
                 query.executeUpdate();
-            } catch (SQLException | NullPointerException exception) {
+            } catch (SQLException exception) {
                 getLogger().error("Error while unlinking player", exception);
                 throw new CompletionException("Error while unlinking player", exception);
             }
@@ -164,10 +169,11 @@ public class SqliteDatabase extends CommonPlayerLink {
     }
 
     @Override
+    @NonNull
     public CompletableFuture<String> createLinkRequest(
-            UUID javaId,
+            @NonNull UUID javaId,
-            String javaUsername,
+            @NonNull String javaUsername,
-            String bedrockUsername
+            @NonNull String bedrockUsername
     ) {
         return CompletableFuture.supplyAsync(() -> {
             LinkRequest request =
@@ -180,11 +186,12 @@ public class SqliteDatabase extends CommonPlayerLink {
     }
 
     @Override
+    @NonNull
     public CompletableFuture<LinkRequestResult> verifyLinkRequest(
-            UUID bedrockId,
+            @NonNull UUID bedrockId,
-            String javaUsername,
+            @NonNull String javaUsername,
-            String bedrockUsername,
+            @NonNull String bedrockUsername,
-            String code
+            @NonNull String code
     ) {
         return CompletableFuture.supplyAsync(() -> {
             LinkRequest request = activeLinkRequests.get(javaUsername);

pom.xml

@@ -84,4 +84,47 @@
   <repositories>
 
   </repositories>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-pmd-plugin</artifactId>
+        <version>3.14.0</version>
+        <configuration>
+          <rulesets>
+            <ruleset>${session.executionRootDirectory}/ruleset.xml</ruleset>
+          </rulesets>
+          <printFailingErrors>true</printFailingErrors>
+        </configuration>
+        <executions>
+          <execution>
+            <goals>
+              <goal>check</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+
+  <reporting>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-pmd-plugin</artifactId>
+        <version>3.14.0</version>
+        <configuration>
+          <rulesets>
+            <ruleset>${session.executionRootDirectory}/ruleset.xml</ruleset>
+          </rulesets>
+        </configuration>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-jxr-plugin</artifactId>
+        <version>2.3</version>
+      </plugin>
+    </plugins>
+  </reporting>
 </project>

ruleset.xml

@@ -0,0 +1,44 @@
+<?xml version="1.0"?>
+<ruleset name="Floodgate Rules"
+  xmlns="http://pmd.sourceforge.net/ruleset/2.0.0"
+  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 https://pmd.sourceforge.io/ruleset_2_0_0.xsd">
+
+  <description>
+    Floodgate Code ruleset
+  </description>
+
+  <exclude-pattern>.*/ReflectionUtils.*</exclude-pattern>
+  <exclude-pattern>.*/CommonPlayerLink.*</exclude-pattern><!-- UnusedPrivateMethod -->
+  <exclude-pattern>.*/DefaultConfigHandler.*</exclude-pattern><!-- NullAssignment -->
+  <exclude-pattern>.*/ConfigFileUpdater.*</exclude-pattern><!-- NullAssignment -->
+  <exclude-pattern>.*/FloodgateConfig.*</exclude-pattern><!-- RedundantFieldInitializer -->
+
+  <rule ref="category/java/bestpractices.xml/MissingOverride" />
+  <rule ref="category/java/bestpractices.xml/UseCollectionIsEmpty" />
+  <rule ref="category/java/bestpractices.xml/UseTryWithResources" />
+
+  <rule ref="category/java/errorprone.xml/CloseResource" />
+  <rule ref="category/java/errorprone.xml/UseLocaleWithCaseConversions" />
+
+  <!-- got a bit lazy, just added whole sections and excluded some unnecessary ones -->
+  <rule ref="category/java/bestpractices.xml">
+    <!-- maybe add these ones back later on -->
+    <exclude name="AvoidPrintStackTrace" />
+    <exclude name="GuardLogStatement" />
+  </rule>
+  <rule ref="category/java/errorprone.xml">
+    <exclude name="AvoidDuplicateLiterals" />
+    <exclude name="AvoidLiteralsInIfCondition" /><!-- Some things just don't change :shrug: -->
+    <exclude name="AvoidFieldNameMatchingMethodName" />
+    <exclude name="BeanMembersShouldSerialize" />
+    <exclude name="UseProperClassLoader" />
+  </rule>
+  <rule ref="category/java/performance.xml">
+    <exclude name="AvoidUsingShortType" />
+    <exclude name="AvoidInstantiatingObjectsInLoops" /><!-- this is ok to some extend -->
+    <exclude name="InefficientStringBuffering" />
+  </rule>
+  <rule ref="category/java/security.xml" />
+
+</ruleset>

spigot/src/main/java/org/geysermc/floodgate/addon/data/SpigotDataHandler.java

@@ -126,7 +126,7 @@ public final class SpigotDataHandler extends SimpleChannelInboundHandler<Object>
         Enum<?>[] protocolStates = (Enum<?>[]) PROTOCOL_STATE.getType().getEnumConstants();
         Object readyToAcceptState = null;
         for (Enum<?> protocolState : protocolStates) {
-            if (protocolState.name().equals("READY_TO_ACCEPT")) {
+            if ("READY_TO_ACCEPT".equals(protocolState.name())) {
                 readyToAcceptState = protocolState;
             }
         }

spigot/src/main/java/org/geysermc/floodgate/inject/spigot/SpigotInjector.java

@@ -50,7 +50,7 @@ public final class SpigotInjector extends CommonPlatformInjector {
     private Object serverConnection;
     private String injectedFieldName;
 
-    @Getter private boolean injected = false;
+    @Getter private boolean injected;
 
     @Override
     @SuppressWarnings("SynchronizationOnLocalVariableOrMethodParameter")
@@ -148,7 +148,6 @@ public final class SpigotInjector extends CommonPlatformInjector {
             }
         }
 
-        injectedFieldName = null;
         injected = false;
         return true;
     }
@@ -162,7 +161,7 @@ public final class SpigotInjector extends CommonPlatformInjector {
 
         Object minecraftServerInstance = ReflectionUtils.invokeStatic(minecraftServer, "getServer");
         for (Method method : minecraftServer.getDeclaredMethods()) {
-            if (method.getReturnType().getSimpleName().equals("ServerConnection")) {
+            if ("ServerConnection".equals(method.getReturnType().getSimpleName())) {
                 if (method.getParameterTypes().length == 0) {
                     serverConnection = method.invoke(minecraftServerInstance);
                 }

spigot/src/main/java/org/geysermc/floodgate/pluginmessage/SpigotSkinApplier.java

@@ -57,8 +57,7 @@ public final class SpigotSkinApplier implements SkinApplier {
     public SpigotSkinApplier(
             SpigotVersionSpecificMethods versionSpecificMethods,
             SpigotPlugin plugin,
-            FloodgateConfigHolder configHolder
+            FloodgateConfigHolder configHolder) {
-    ) {
         this.versionSpecificMethods = versionSpecificMethods;
         this.plugin = plugin;
         this.configHolder = configHolder;
@@ -89,7 +88,7 @@ public final class SpigotSkinApplier implements SkinApplier {
             // By running as a task, we don't run into async issues
             plugin.getServer().getScheduler().runTask(plugin, () -> {
                 for (Player p : Bukkit.getOnlinePlayers()) {
-                    if (p != player && p.canSee(player)) {
+                    if (!p.equals(player) && p.canSee(player)) {
                         versionSpecificMethods.hidePlayer(p, player);
                         versionSpecificMethods.showPlayer(p, player);
                     }

spigot/src/main/java/org/geysermc/floodgate/util/SpigotCommandUtil.java

@@ -60,6 +60,7 @@ public final class SpigotCommandUtil implements CommandUtil {
     private final FloodgateLogger logger;
     private final LanguageManager manager;
 
+    @Override
     public @NonNull UserAudience getAudience(final @NonNull Object sourceObj) {
         if (!(sourceObj instanceof CommandSender)) {
             throw new IllegalArgumentException("Source has to be a CommandSender!");
@@ -116,14 +117,14 @@ public final class SpigotCommandUtil implements CommandUtil {
                 break;
             case ONLY_JAVA:
                 for (Player player : players) {
-                    if (!api.isBedrockPlayer(player.getUniqueId())) {
+                    if (!api.isFloodgatePlayer(player.getUniqueId())) {
                         usernames.add(player.getName());
                     }
                 }
                 break;
             case ONLY_BEDROCK:
                 for (Player player : players) {
-                    if (api.isBedrockPlayer(player.getUniqueId())) {
+                    if (api.isFloodgatePlayer(player.getUniqueId())) {
                         usernames.add(player.getName());
                     }
                 }

velocity/src/main/java/org/geysermc/floodgate/addon/data/VelocityProxyDataHandler.java

@@ -106,6 +106,7 @@ public final class VelocityProxyDataHandler extends SimpleChannelInboundHandler<
                 break;
             case EXCEPTION:
                 ctx.channel().attr(kickMessageAttribute).set(config.getDisconnect().getInvalidKey());
+                return;
             case INVALID_DATA_LENGTH:
                 ctx.channel().attr(kickMessageAttribute)
                         .set(config.getDisconnect().getInvalidArgumentsLength());

velocity/src/main/java/org/geysermc/floodgate/addon/data/VelocityServerDataHandler.java

@@ -110,7 +110,7 @@ public final class VelocityServerDataHandler extends MessageToMessageEncoder<Obj
         checkArgument(encryptedData != null, "Encrypted data cannot be null");
 
         // use the same system that we use on bungee, our data goes before all the other data
-        int addressFinished = address.indexOf("\0");
+        int addressFinished = address.indexOf('\0');
         String originalAddress = address.substring(0, addressFinished);
         String remaining = address.substring(addressFinished);
 

velocity/src/main/java/org/geysermc/floodgate/inject/velocity/VelocityInjector.java

@@ -44,8 +44,9 @@ public final class VelocityInjector extends CommonPlatformInjector {
     private final ProxyServer server;
     private final FloodgateLogger logger;
 
-    @Getter private boolean injected = false;
+    @Getter private boolean injected;
 
+    @Override
     @SuppressWarnings("rawtypes")
     public boolean inject() {
         if (isInjected()) {

velocity/src/main/java/org/geysermc/floodgate/listener/VelocityPluginMessageHandler.java

@@ -25,7 +25,9 @@
 
 package org.geysermc.floodgate.listener;
 
+import com.google.gson.JsonIOException;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonSyntaxException;
 import com.google.inject.Inject;
 import com.google.inject.name.Named;
 import com.velocitypowered.api.event.Subscribe;
@@ -165,7 +167,7 @@ public class VelocityPluginMessageHandler extends PluginMessageHandler {
                 try {
                     Reader reader = new InputStreamReader(new ByteArrayInputStream(responseData));
                     response = GSON.fromJson(reader, JsonObject.class);
-                } catch (Throwable throwable) {
+                } catch (JsonIOException | JsonSyntaxException throwable) {
                     logger.error("Failed to read Skin response", throwable);
                     return;
                 }

velocity/src/main/java/org/geysermc/floodgate/util/VelocityCommandUtil.java

@@ -115,14 +115,14 @@ public final class VelocityCommandUtil implements CommandUtil {
                 break;
             case ONLY_JAVA:
                 for (Player player : players) {
-                    if (!api.isBedrockPlayer(player.getUniqueId())) {
+                    if (!api.isFloodgatePlayer(player.getUniqueId())) {
                         usernames.add(player.getUsername());
                     }
                 }
                 break;
             case ONLY_BEDROCK:
                 for (Player player : players) {
-                    if (api.isBedrockPlayer(player.getUniqueId())) {
+                    if (api.isFloodgatePlayer(player.getUniqueId())) {
                         usernames.add(player.getUsername());
                     }
                 }