服务器回调客户端

通过参数回调从服务器端调用客户端逻辑

功能描述

参数回调方法与调用本地回调或监听器相同，您只需要在 Spring 配置文件中声明哪个参数是回调类型。Dubbo 将基于持久连接生成一个反向代理，以便可以从服务器端调用客户端逻辑。您可以参考 dubbo 项目中的示例代码.

使用场景

回调函数通知客户端执行结果，或发送通知。当方法执行时间较长时，类似于异步调用，在审批流程中回调客户端审批结果。

如何使用

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);
}

服务提供者接口实现示例

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); // Timely trigger change notification
                    } catch (Throwable t) { // defensive fault tolerance
                        t. printStackTrace();
                    }
                }
            }
        });
        t. setDaemon(true);
        t. start();
    }
  
    public void addListener(String key, CallbackListener listener) {
        listeners. put(key, listener);
        listener.changed(getChanged(key)); // send change notification
    }
     
    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" />
        <!--You can also specify the type -->
        <!--<dubbo:argument type="com.demo.CallbackListener" callback="true" />-->
    </dubbo:method>
</dubbo:service>

服务消费者配置示例

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

服务消费者调用示例

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

上次修改时间：2023 年 1 月 2 日：增强 en 文档 (#1798) (95a9f4f6c1c)