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 listeners = new ConcurrentHashMap();

    public CallbackServiceImpl() {
        Thread t = new Thread( new Runnable() {
            public void run() {
                while ( true ) {
                    try {
                        for (Map.Entry 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" />


    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 Java代码   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