| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.ahc.util; |
| |
| import java.util.List; |
| import java.util.concurrent.CopyOnWriteArrayList; |
| import java.util.concurrent.ExecutorService; |
| import java.util.concurrent.Executors; |
| |
| /** |
| * This is an event dispatcher to dispatch monitoring events on separate threads |
| * from the main thread. |
| */ |
| public class EventDispatcher { |
| /** shared thread pool for dispatching events */ |
| private static ExecutorService dispatchThreadPool; |
| |
| /** list of listeners for monitoring events */ |
| private final List<MonitoringListener> listeners = |
| new CopyOnWriteArrayList<MonitoringListener>(); |
| |
| /** |
| * Creates a new EventDispatcher, including starting the new thread. |
| */ |
| public EventDispatcher() { |
| // initialize the thread pool if it is not initialized yet |
| synchronized (EventDispatcher.class) { |
| if (dispatchThreadPool == null) { |
| dispatchThreadPool = Executors.newSingleThreadExecutor(new DaemonThreadFactory()); |
| } |
| } |
| } |
| |
| /** |
| * Add a listener for the dispatched events. |
| * |
| * @param listener The new listener. |
| */ |
| public void addListener(MonitoringListener listener) { |
| listeners.add(listener); |
| } |
| |
| /** |
| * Remove a listener from the dispatch queue. |
| * |
| * @param listener The listener to remove. |
| */ |
| public void removeListener(MonitoringListener listener) { |
| listeners.remove(listener); |
| } |
| |
| /** |
| * Dispatch an event. |
| * |
| * @param event The event to dispatch. |
| */ |
| public void dispatchEvent(final MonitoringEvent event) { |
| // if there's no active listeners, no point in dispatching this |
| if (listeners.isEmpty()) { |
| return; |
| } |
| |
| Runnable job = new Runnable() { |
| public void run() { |
| // iterate through the listeners list calling the handlers. |
| for (MonitoringListener listener : listeners) { |
| try { |
| event.dispatch(listener); |
| } catch (Throwable e) { |
| // just eat these |
| } |
| } |
| } |
| }; |
| dispatchThreadPool.execute(job); |
| } |
| } |