com.google.common.eventbus.AnnotatedHandlerFinder Maven / Gradle / Ivy
/*
* Copyright (C) 2007 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.eventbus;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.Multimap;
import com.google.common.reflect.TypeToken;
import java.lang.reflect.Method;
import java.util.Set;
/**
* A {@link HandlerFindingStrategy} for collecting all event handler methods that are marked with
* the {@link Subscribe} annotation.
*
* @author Cliff Biffle
* @author Louis Wasserman
*/
class AnnotatedHandlerFinder implements HandlerFindingStrategy {
/**
* {@inheritDoc}
*
* This implementation finds all methods marked with a {@link Subscribe} annotation.
*/
@Override
public Multimap, EventHandler> findAllHandlers(Object listener) {
Multimap, EventHandler> methodsInListener = HashMultimap.create();
Class clazz = listener.getClass();
Set> supers = TypeToken.of(clazz).getTypes().rawTypes();
for (Method method : clazz.getMethods()) {
/*
* Iterate over each distinct method of {@code clazz}, checking if it is annotated with
* @Subscribe by any of the superclasses or superinterfaces that declare it.
*/
for (Class c : supers) {
try {
Method m = c.getMethod(method.getName(), method.getParameterTypes());
if (m.isAnnotationPresent(Subscribe.class)) {
Class[] parameterTypes = method.getParameterTypes();
if (parameterTypes.length != 1) {
throw new IllegalArgumentException("Method " + method
+ " has @Subscribe annotation, but requires " + parameterTypes.length
+ " arguments. Event handler methods must require a single argument.");
}
Class eventType = parameterTypes[0];
EventHandler handler = makeHandler(listener, method);
methodsInListener.put(eventType, handler);
break;
}
} catch (NoSuchMethodException ignored) {
// Move on.
}
}
}
return methodsInListener;
}
/**
* Creates an {@code EventHandler} for subsequently calling {@code method} on
* {@code listener}.
* Selects an EventHandler implementation based on the annotations on
* {@code method}.
*
* @param listener object bearing the event handler method.
* @param method the event handler method to wrap in an EventHandler.
* @return an EventHandler that will call {@code method} on {@code listener}
* when invoked.
*/
private static EventHandler makeHandler(Object listener, Method method) {
EventHandler wrapper;
if (methodIsDeclaredThreadSafe(method)) {
wrapper = new EventHandler(listener, method);
} else {
wrapper = new SynchronizedEventHandler(listener, method);
}
return wrapper;
}
/**
* Checks whether {@code method} is thread-safe, as indicated by the
* {@link AllowConcurrentEvents} annotation.
*
* @param method handler method to check.
* @return {@code true} if {@code handler} is marked as thread-safe,
* {@code false} otherwise.
*/
private static boolean methodIsDeclaredThreadSafe(Method method) {
return method.getAnnotation(AllowConcurrentEvents.class) != null;
}
}