dubbo-examples/src/main/java/com/alibaba/dubbo/examples/callback/impl/CallbackServiceImpl.java

/*
 * Copyright 1999-2012 Alibaba Group.
 *  
 * 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.alibaba.dubbo.examples.callback.impl;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import com.alibaba.dubbo.examples.callback.api.CallbackListener;
import com.alibaba.dubbo.examples.callback.api.CallbackService;

/**
 * CallbackServiceImpl
 * 
 * @author william.liangf
 */
public class CallbackServiceImpl implements CallbackService {
    
   private final Map<String, CallbackListener> listeners = new ConcurrentHashMap<String, CallbackListener>();
 
   public CallbackServiceImpl() {
       Thread t = new Thread(new Runnable() {
           public void run() {
               while(true) {
                   try {
                       for(Map.Entry<String, CallbackListener> entry : listeners.entrySet()){
                           try {
                               entry.getValue().changed(getChanged(entry.getKey()));
                           } catch (Throwable t) {
                               listeners.remove(entry.getKey());
                           }
                       }
                       Thread.sleep(5000); // 定时触发变更通知
                   } catch (Throwable t) { // 防御容错
                       t.printStackTrace();
                   }
               }
           }
       });
       t.setDaemon(true);
       t.start();
   }
 
   public void addListener(String key, CallbackListener listener) {
       listeners.put(key, listener);
       listener.changed(getChanged(key)); // 发送变更通知
   }
    
   private String getChanged(String key) {
       return "Changed: " + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
   }

}