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事件通知

在调用之前、调用之后、出现异常时,会触发 oninvokeonreturnonthrow 三个事件,可以配置当事件发生时,通知哪个类的哪个方法 [1]

服务提供者与消费者共享服务接口

interface IDemoService {
    public Person get(int id);
}

服务提供者实现

class NormalDemoService implements IDemoService {
    public Person get(int id) {
        return new Person(id, "charles`son", 4);
    }
}

服务提供者配置

<dubbo:application name="rpc-callback-demo" />
<dubbo:registry address="zookeeper://127.0.0.1:2181"/>
<bean id="demoService" class="org.apache.dubbo.callback.implicit.NormalDemoService" />
<dubbo:service interface="org.apache.dubbo.callback.implicit.IDemoService" ref="demoService" version="1.0.0" group="cn"/>

服务消费者 Callback 接口

interface Notify {
    public void onreturn(Person msg, Integer id);
    public void onthrow(Throwable ex, Integer id);
}

服务消费者 Callback 实现

class NotifyImpl implements Notify {
    public Map<Integer, Person>    ret    = new HashMap<Integer, Person>();
    public Map<Integer, Throwable> errors = new HashMap<Integer, Throwable>();
    
    public void onreturn(Person msg, Integer id) {
        System.out.println("onreturn:" + msg);
        ret.put(id, msg);
    }
    
    public void onthrow(Throwable ex, Integer id) {
        errors.put(id, ex);
    }
}

服务消费者 Callback 配置

<bean id ="demoCallback" class = "org.apache.dubbo.callback.implicit.NofifyImpl" />
<dubbo:reference id="demoService" interface="org.apache.dubbo.callback.implicit.IDemoService" version="1.0.0" group="cn" >
      <dubbo:method name="get" async="true" onreturn = "demoCallback.onreturn" onthrow="demoCallback.onthrow" />
</dubbo:reference>

callbackasync 功能正交分解,async=true 表示结果是否马上返回,onreturn 表示是否需要回调。

两者叠加存在以下几种组合情况 [2]

  • 异步回调模式:async=true onreturn="xxx"
  • 同步回调模式:async=false onreturn="xxx"
  • 异步无回调 :async=true
  • 同步无回调 :async=false

测试代码

IDemoService demoService = (IDemoService) context.getBean("demoService");
NofifyImpl notify = (NofifyImpl) context.getBean("demoCallback");
int requestId = 2;
Person ret = demoService.get(requestId);
Assert.assertEquals(null, ret);
//for Test:只是用来说明callback正常被调用,业务具体实现自行决定.
for (int i = 0; i < 10; i++) {
    if (!notify.ret.containsKey(requestId)) {
        Thread.sleep(200);
    } else {
        break;
    }
}
Assert.assertEquals(requestId, notify.ret.get(requestId).getId());

  1. 支持版本:2.0.7 之后 ↩︎

  2. async=false 默认 ↩︎