Use custom AnnotatedHandlerFinder and pretend all events are thread safe
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/*
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* Copyright (C) 2007 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.eventbus;
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import com.google.common.base.Throwables;
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import com.google.common.cache.CacheBuilder;
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import com.google.common.cache.CacheLoader;
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import com.google.common.cache.LoadingCache;
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import com.google.common.collect.HashMultimap;
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import com.google.common.collect.ImmutableList;
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import com.google.common.collect.Multimap;
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import com.google.common.reflect.TypeToken;
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import com.google.common.util.concurrent.UncheckedExecutionException;
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import java.lang.reflect.Method;
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import java.util.Set;
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/**
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* A {@link HandlerFindingStrategy} for collecting all event handler methods that are marked with
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* the {@link Subscribe} annotation.
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*
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* @author Cliff Biffle
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* @author Louis Wasserman
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*/
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class AnnotatedHandlerFinder implements HandlerFindingStrategy {
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/**
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* A thread-safe cache that contains the mapping from each class to all methods in that class and
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* all super-classes, that are annotated with {@code @Subscribe}. The cache is shared across all
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* instances of this class; this greatly improves performance if multiple EventBus instances are
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* created and objects of the same class are registered on all of them.
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*/
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private static final LoadingCache<Class<?>, ImmutableList<Method>> handlerMethodsCache =
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CacheBuilder.newBuilder()
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.weakKeys()
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.build(new CacheLoader<Class<?>, ImmutableList<Method>>() {
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@Override
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public ImmutableList<Method> load(Class<?> concreteClass) throws Exception {
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return getAnnotatedMethodsInternal(concreteClass);
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}
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});
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/**
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* {@inheritDoc}
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*
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* This implementation finds all methods marked with a {@link Subscribe} annotation.
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*/
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@Override
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public Multimap<Class<?>, EventHandler> findAllHandlers(Object listener) {
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Multimap<Class<?>, EventHandler> methodsInListener = HashMultimap.create();
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Class<?> clazz = listener.getClass();
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for (Method method : getAnnotatedMethods(clazz)) {
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Class<?>[] parameterTypes = method.getParameterTypes();
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Class<?> eventType = parameterTypes[0];
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EventHandler handler = new EventHandler(listener, method);
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methodsInListener.put(eventType, handler);
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}
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return methodsInListener;
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}
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private static ImmutableList<Method> getAnnotatedMethods(Class<?> clazz) {
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try {
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return handlerMethodsCache.getUnchecked(clazz);
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} catch (UncheckedExecutionException e) {
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throw Throwables.propagate(e.getCause());
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}
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}
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private static ImmutableList<Method> getAnnotatedMethodsInternal(Class<?> clazz) {
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Set<? extends Class<?>> supers = TypeToken.of(clazz).getTypes().rawTypes();
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ImmutableList.Builder<Method> result = ImmutableList.builder();
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for (Method method : clazz.getMethods()) {
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/*
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* Iterate over each distinct method of {@code clazz}, checking if it is annotated with
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* @Subscribe by any of the superclasses or superinterfaces that declare it.
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*/
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for (Class<?> c : supers) {
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try {
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Method m = c.getMethod(method.getName(), method.getParameterTypes());
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if (m.isAnnotationPresent(Subscribe.class)) {
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Class<?>[] parameterTypes = method.getParameterTypes();
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if (parameterTypes.length != 1) {
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throw new IllegalArgumentException("Method " + method
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+ " has @Subscribe annotation, but requires " + parameterTypes.length
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+ " arguments. Event handler methods must require a single argument.");
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}
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Class<?> eventType = parameterTypes[0];
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result.add(method);
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break;
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}
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} catch (NoSuchMethodException ignored) {
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// Move on.
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}
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}
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}
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return result.build();
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}
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}
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