1 /* 2 * Copyright (C) 2007 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.eventbus; 18 19 import com.google.common.collect.HashMultimap; 20 import com.google.common.collect.Multimap; 21 import java.lang.reflect.Method; 22 23 /** 24 * A {@link HandlerFindingStrategy} for collecting all event handler methods 25 * that are marked with the {@link Subscribe} annotation. 26 * 27 * @author Cliff Biffle 28 */ 29 class AnnotatedHandlerFinder implements HandlerFindingStrategy { 30 31 /** 32 * {@inheritDoc} 33 * 34 * This implementation finds all methods marked with a {@link Subscribe} 35 * annotation. 36 */ 37 @Override findAllHandlers(Object listener)38 public Multimap<Class<?>, EventHandler> findAllHandlers(Object listener) { 39 Multimap<Class<?>, EventHandler> methodsInListener = 40 HashMultimap.create(); 41 Class clazz = listener.getClass(); 42 while (clazz != null) { 43 for (Method method : clazz.getMethods()) { 44 Subscribe annotation = method.getAnnotation(Subscribe.class); 45 46 if (annotation != null) { 47 Class<?>[] parameterTypes = method.getParameterTypes(); 48 if (parameterTypes.length != 1) { 49 throw new IllegalArgumentException( 50 "Method " + method + " has @Subscribe annotation, but requires " + 51 parameterTypes.length + " arguments. Event handler methods " + 52 "must require a single argument."); 53 } 54 Class<?> eventType = parameterTypes[0]; 55 EventHandler handler = makeHandler(listener, method); 56 57 methodsInListener.put(eventType, handler); 58 } 59 } 60 clazz = clazz.getSuperclass(); 61 } 62 return methodsInListener; 63 } 64 65 /** 66 * Creates an {@code EventHandler} for subsequently calling {@code method} on 67 * {@code listener}. 68 * Selects an EventHandler implementation based on the annotations on 69 * {@code method}. 70 * 71 * @param listener object bearing the event handler method. 72 * @param method the event handler method to wrap in an EventHandler. 73 * @return an EventHandler that will call {@code method} on {@code listener} 74 * when invoked. 75 */ makeHandler(Object listener, Method method)76 private static EventHandler makeHandler(Object listener, Method method) { 77 EventHandler wrapper; 78 if (methodIsDeclaredThreadSafe(method)) { 79 wrapper = new EventHandler(listener, method); 80 } else { 81 wrapper = new SynchronizedEventHandler(listener, method); 82 } 83 return wrapper; 84 } 85 86 /** 87 * Checks whether {@code method} is thread-safe, as indicated by the 88 * {@link AllowConcurrentEvents} annotation. 89 * 90 * @param method handler method to check. 91 * @return {@code true} if {@code handler} is marked as thread-safe, 92 * {@code false} otherwise. 93 */ methodIsDeclaredThreadSafe(Method method)94 private static boolean methodIsDeclaredThreadSafe(Method method) { 95 return method.getAnnotation(AllowConcurrentEvents.class) != null; 96 } 97 } 98