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

参数回调实现了在客户端调用服务时，将回调方法做为参数传递给服务端。当服务端提供服务时会调用执行客户回调方法，从而执行客户端自定义的一些操作

 

 

 

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);

    }

});

 

 

 执行结果

callback1:Changed: 2016-06-17 14:15:05
callback2:Changed: 2016-06-17 14:15:05
callback2:Changed: 2016-06-17 14:15:06
callback1:Changed: 2016-06-17 14:15:06
callback2:Changed: 2016-06-17 14:15:11