Use MethodHandle for faster event bus (#1865)

* Use MethodHandle for faster event bus

* Implement hashCode/equals

* Apply review comments

* Bind to the object directly

worldedit-core/src/main/java/com/sk89q/worldedit/util/eventbus/AnnotatedSubscriberFinder.java

@@ -22,6 +22,8 @@
 import com.google.common.collect.HashMultimap;
 import com.google.common.collect.Multimap;
 
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
 import java.lang.reflect.Method;
 
 /**
@@ -59,7 +61,14 @@ public Multimap<Class<?>, EventHandler> findAllSubscribers(Object listener) {
                         );
                     }
                     Class<?> eventType = parameterTypes[0];
-                    EventHandler handler = new MethodEventHandler(annotation.priority(), listener, method);
+                    MethodHandle handle;
+                    try {
+                        handle = MethodHandles.publicLookup().unreflect(method);
+                    } catch (IllegalAccessException e) {
+                        throw new IllegalArgumentException("Method " + method + " failed to unreflect.", e);
+                    }
+
+                    EventHandler handler = new MethodHandleEventHandler(annotation.priority(), listener, handle, method.getName());
                     methodsInListener.put(eventType, handler);
                 }
             }

worldedit-core/src/main/java/com/sk89q/worldedit/util/eventbus/MethodEventHandler.java

@@ -20,6 +20,7 @@
 package com.sk89q.worldedit.util.eventbus;
 
 import java.lang.reflect.Method;
+import java.util.Objects;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
@@ -72,11 +73,8 @@ public boolean equals(Object o) {
         if (!method.equals(that.method)) {
             return false;
         }
-        if (object != null ? !object.equals(that.object) : that.object != null) {
-            return false;
-        }
 
-        return true;
+        return Objects.equals(object, that.object);
     }
 
     @Override

worldedit-core/src/main/java/com/sk89q/worldedit/util/eventbus/MethodHandleEventHandler.java

@@ -0,0 +1,82 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.util.eventbus;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodType;
+import java.util.Objects;
+
+public class MethodHandleEventHandler extends EventHandler {
+
+    private final MethodHandle methodHandle;
+    private final String methodName;
+    private final Object object;
+
+    /**
+     * Create a new event handler that uses MethodHandles to dispatch.
+     *
+     * @param priority the priority
+     * @param object The object to invoke it on
+     * @param methodHandle The handle to invoke
+     * @param methodName The name of the method (for equality checks)
+     */
+    protected MethodHandleEventHandler(Priority priority, Object object, MethodHandle methodHandle, String methodName) {
+        super(priority);
+
+        this.object = object;
+        this.methodHandle = methodHandle.bindTo(object).asType(MethodType.methodType(void.class, Object.class));
+        this.methodName = methodName;
+    }
+
+    @Override
+    public void dispatch(Object event) throws Exception {
+        try {
+            this.methodHandle.invokeExact(event);
+        } catch (Exception | Error e) {
+            throw e;
+        } catch (Throwable t) {
+            // If it's not an Exception or Error, throw it wrapped.
+            throw new Exception(t);
+        }
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(methodName, object);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        MethodHandleEventHandler that = (MethodHandleEventHandler) o;
+
+        if (!methodName.equals(that.methodName)) {
+            return false;
+        }
+
+        return Objects.equals(object, that.object);
+    }
+}