Support multiple plugins loaded from the same JAR

annotation-processor/src/main/java/com/velocitypowered/annotationprocessor/ApiAnnotationProcessor.java

@@ -28,6 +28,7 @@ import com.velocitypowered.api.plugin.Plugin;
 import java.io.BufferedWriter;
 import java.io.IOException;
 import java.io.Writer;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 import java.util.Set;
@@ -56,9 +57,6 @@ import javax.tools.StandardLocation;
 @SupportedAnnotationTypes({PLUGIN_ANNOTATION_CLASS, SUBSCRIBE_ANNOTATION_CLASS})
 public class ApiAnnotationProcessor extends AbstractProcessor {
 
-  private @Nullable String pluginClassFound;
-  private boolean warnedAboutMultiplePlugins;
-
   @Override
   public SourceVersion getSupportedSourceVersion() {
     return SourceVersion.latestSupported();
@@ -107,6 +105,7 @@ public class ApiAnnotationProcessor extends AbstractProcessor {
     }
 
     if (ProcessorUtils.contains(annotations, Plugin.class)) {
+      List<SerializedPluginDescription> found = new ArrayList<>();
       for (Element element : roundEnv.getElementsAnnotatedWith(Plugin.class)) {
         if (element.getKind() != ElementKind.CLASS) {
           processingEnv.getMessager()
@@ -117,17 +116,6 @@ public class ApiAnnotationProcessor extends AbstractProcessor {
 
         Name qualifiedName = ((TypeElement) element).getQualifiedName();
 
-        if (Objects.equals(pluginClassFound, qualifiedName.toString())) {
-          if (!warnedAboutMultiplePlugins) {
-            processingEnv.getMessager()
-                .printMessage(Diagnostic.Kind.WARNING,
-                    "Velocity does not yet currently support multiple plugins. "
-                        + "We are using " + pluginClassFound + " for your plugin's main class.");
-            warnedAboutMultiplePlugins = true;
-          }
-          return false;
-        }
-
         Plugin plugin = element.getAnnotation(Plugin.class);
         if (!SerializedPluginDescription.ID_PATTERN.matcher(plugin.id()).matches()) {
           processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR,
@@ -137,24 +125,25 @@ public class ApiAnnotationProcessor extends AbstractProcessor {
           return false;
         }
 
-        // All good, generate the velocity-plugin.json.
+        // All good, generate the velocity-plugin-info.json.
         SerializedPluginDescription description = SerializedPluginDescription
             .from(plugin, qualifiedName.toString());
+        found.add(description);
+      }
+
       try {
         FileObject object = processingEnv.getFiler()
-              .createResource(StandardLocation.CLASS_OUTPUT, "", "velocity-plugin.json");
+            .createResource(StandardLocation.CLASS_OUTPUT, "", "velocity-plugin-info.json");
         try (Writer writer = new BufferedWriter(object.openWriter())) {
-            new Gson().toJson(description, writer);
+          new Gson().toJson(found, writer);
         }
         processingEnv.getMessager().printMessage(Diagnostic.Kind.NOTE,
-              "Wrote velocity-plugin.json to " + object.toUri().toString());
+            "Wrote velocity-plugin-info.json to " + object.toUri().toString());
-          pluginClassFound = qualifiedName.toString();
       } catch (IOException e) {
         processingEnv.getMessager()
             .printMessage(Diagnostic.Kind.ERROR, "Unable to generate plugin file");
       }
     }
-    }
 
     return false;
   }

proxy/src/main/java/com/velocitypowered/proxy/plugin/VelocityPluginManager.java

@@ -49,12 +49,10 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.IdentityHashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.checkerframework.checker.nullness.qual.Nullable;
@@ -100,7 +98,7 @@ public class VelocityPluginManager implements PluginManager {
         p -> p.toFile().isFile() && p.toString().endsWith(".jar"))) {
       for (Path path : stream) {
         try {
-          found.add(loader.loadPluginDescription(path));
+          found.addAll(loader.loadPluginCandidates(path));
         } catch (Exception e) {
           logger.error("Unable to load plugin {}", path, e);
         }
@@ -160,7 +158,7 @@ public class VelocityPluginManager implements PluginManager {
       }
 
       try {
-        PluginDescription realPlugin = loader.loadPlugin(candidate);
+        PluginDescription realPlugin = loader.materializePlugin(candidate);
         VelocityPluginContainer container = new VelocityPluginContainer(realPlugin);
         pluginContainers.put(container, loader.createModule(container));
         loadedPluginsById.put(candidate.id(), container);

proxy/src/main/java/com/velocitypowered/proxy/plugin/loader/PluginLoader.java

@@ -21,15 +21,16 @@ import com.google.inject.Module;
 import com.velocitypowered.api.plugin.PluginContainer;
 import com.velocitypowered.api.plugin.PluginDescription;
 import java.nio.file.Path;
+import java.util.Collection;
 
 /**
  * This interface is used for loading plugins.
  */
 public interface PluginLoader {
 
-  PluginDescription loadPluginDescription(Path source) throws Exception;
+  Collection<PluginDescription> loadPluginCandidates(Path source) throws Exception;
 
-  PluginDescription loadPlugin(PluginDescription source) throws Exception;
+  PluginDescription materializePlugin(PluginDescription source) throws Exception;
 
   /**
    * Creates a {@link Module} for the provided {@link PluginContainer}

proxy/src/main/java/com/velocitypowered/proxy/plugin/loader/java/JavaPluginLoader.java

@@ -31,16 +31,23 @@ import com.velocitypowered.proxy.plugin.PluginClassLoader;
 import com.velocitypowered.proxy.plugin.loader.PluginLoader;
 import com.velocitypowered.proxy.plugin.loader.VelocityPluginContainer;
 import com.velocitypowered.proxy.plugin.loader.VelocityPluginDescription;
+import io.leangen.geantyref.TypeToken;
 import java.io.BufferedInputStream;
 import java.io.InputStreamReader;
 import java.io.Reader;
+import java.net.URI;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
 import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.jar.JarEntry;
 import java.util.jar.JarInputStream;
@@ -49,27 +56,28 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 public class JavaPluginLoader implements PluginLoader {
 
   private final Path baseDirectory;
+  private final Map<URI, PluginClassLoader> classLoaders = new HashMap<>();
 
   public JavaPluginLoader(ProxyServer server, Path baseDirectory) {
     this.baseDirectory = baseDirectory;
   }
 
   @Override
-  public PluginDescription loadPluginDescription(Path source) throws Exception {
+  public Collection<PluginDescription> loadPluginCandidates(Path source) throws Exception {
-    SerializedPluginDescription serialized = getSerializedPluginInfo(source);
+    List<SerializedPluginDescription> serialized = getSerializedPluginInfo(source);
-    if (serialized == null) {
+    if (serialized.isEmpty()) {
-      throw new InvalidPluginException("Did not find a valid velocity-plugin.json.");
+      throw new InvalidPluginException("Did not find a valid velocity-plugin-info.json.");
     }
 
-    if (!SerializedPluginDescription.ID_PATTERN.matcher(serialized.getId()).matches()) {
+    List<PluginDescription> candidates = new ArrayList<>();
-      throw new InvalidPluginException("Plugin ID '" + serialized.getId() + "' is invalid.");
+    for (SerializedPluginDescription description : serialized) {
+      candidates.add(createCandidateDescription(description, source));
     }
-
+    return candidates;
-    return createCandidateDescription(serialized, source);
   }
 
   @Override
-  public PluginDescription loadPlugin(PluginDescription source) throws Exception {
+  public PluginDescription materializePlugin(PluginDescription source) throws Exception {
     if (!(source instanceof JavaVelocityPluginDescriptionCandidate)) {
       throw new IllegalArgumentException("Description provided isn't of the Java plugin loader");
     }
@@ -79,11 +87,15 @@ public class JavaPluginLoader implements PluginLoader {
       throw new IllegalStateException("JAR path not provided.");
     }
 
-    URL pluginJarUrl = jarFilePath.toUri().toURL();
+    URI pluginJarUri = jarFilePath.toUri();
-    PluginClassLoader loader = AccessController.doPrivileged(
+    URL pluginJarUrl = pluginJarUri.toURL();
+    PluginClassLoader loader = this.classLoaders.computeIfAbsent(pluginJarUri, (uri) -> {
+      PluginClassLoader classLoader = AccessController.doPrivileged(
           (PrivilegedAction<PluginClassLoader>) () -> new PluginClassLoader(new URL[]{pluginJarUrl},
               source));
-    loader.addToClassloaders();
+      classLoader.addToClassloaders();
+      return classLoader;
+    });
 
     JavaVelocityPluginDescriptionCandidate candidate =
         (JavaVelocityPluginDescriptionCandidate) source;
@@ -130,32 +142,43 @@ public class JavaPluginLoader implements PluginLoader {
     ((VelocityPluginContainer) container).setInstance(instance);
   }
 
-  private @Nullable SerializedPluginDescription getSerializedPluginInfo(Path source)
+  private List<SerializedPluginDescription> getSerializedPluginInfo(Path source)
       throws Exception {
+    boolean foundOldVelocityPlugin = false;
     boolean foundBungeeBukkitPluginFile = false;
     try (JarInputStream in = new JarInputStream(
         new BufferedInputStream(Files.newInputStream(source)))) {
       JarEntry entry;
       while ((entry = in.getNextJarEntry()) != null) {
-        if (entry.getName().equals("velocity-plugin.json")) {
+        if (entry.getName().equals("velocity-plugin-info.json")) {
           try (Reader pluginInfoReader = new InputStreamReader(in, StandardCharsets.UTF_8)) {
             return VelocityServer.GENERAL_GSON.fromJson(pluginInfoReader,
-                SerializedPluginDescription.class);
+                new TypeToken<List<SerializedPluginDescription>>() {}.getType());
           }
         }
 
+        if (entry.getName().equals("velocity-plugin.json")) {
+          foundOldVelocityPlugin = true;
+        }
+
         if (entry.getName().equals("plugin.yml") || entry.getName().equals("bungee.yml")) {
           foundBungeeBukkitPluginFile = true;
         }
       }
 
+      if (foundOldVelocityPlugin) {
+        throw new InvalidPluginException("The plugin file " + source.getFileName() + " appears to "
+            + "be developed for an older version of Velocity. Please obtain a newer version of the "
+            + "plugin.");
+      }
+
       if (foundBungeeBukkitPluginFile) {
         throw new InvalidPluginException("The plugin file " + source.getFileName() + " appears to "
             + "be a Bukkit or BungeeCord plugin. Velocity does not support Bukkit or BungeeCord "
             + "plugins.");
       }
 
-      return null;
+      return List.of();
     }
   }