dubbo高级应用回调

dubbo高级应用回调

dubbo的回调和本地的回调机制一致，在服务提供端配置回调的方法时为了dubbo能把消费端的回调对像传到提供端

参数回调方式与调用本地callback或listener相同，只需要在Spring的配置文件中声明哪个参数是callback类型即可，Dubbo将基于长连接生成反向代理，这样就可以从服务器端调用客户端逻辑。

2.0.6及其以上版本支持

代码参见：https://github.com/alibaba/dubbo/tree/master/dubbo-test/dubbo-test-examples/src/main/java/com/alibaba/dubbo/examples/callback

(1) 共享服务接口：

服务接口示例：

CallbackService.java

package com.callback;   public interface CallbackService {      void addListener(String key, CallbackListener listener); }

CallbackListener.java

package com.callback;   public interface CallbackListener {      void changed(String msg); }

(2) 服务提供者：

服务提供者接口实现示例：

CallbackServiceImpl.java

package com.callback.impl;   import java.text.SimpleDateFormat; import java.util.Date; import java.util.Map; import java.util.concurrent.ConcurrentHashMap;   import com.callback.CallbackListener; import com.callback.CallbackService;   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（不用定时方式）      }            private String getChanged(String key) {          return "Changed: " + new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss" ).format( new Date());      }   }

服务提供者配置示例：

< bean id = "callbackService" class = "com.callback.impl.CallbackServiceImpl" /> < dubbo:service interface = "com.callback.CallbackService" ref = "callbackService" connections = "1" callbacks = "1000" >      < dubbo:method name = "addListener" >          < dubbo:argument index = "1" callback = "true" />          <!--也可以通过指定类型的方式-->          <!--<dubbo:argument type="com.demo.CallbackListener" callback="true" />-->      </ dubbo:method > </ dubbo:service >

(2) 服务消费者：

服务消费者配置示例：

consumer.xml

< dubbo:reference id = "callbackService" interface = "com.callback.CallbackService" />

服务消费者调用示例：

CallbackServiceTest.java

ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext( "classpath:consumer.xml" ); context.start();   CallbackService callbackService = (CallbackService) context.getBean( "callbackService" );   callbackService.addListener( "http://10.20.160.198/wiki/display/dubbo/foo.bar" , new CallbackListener(){      public void changed(String msg) {          System.out.println( "callback1:" + msg);      } });