在调用之前、调用之后、出现异常时,会触发 oninvoke
、onreturn
、onthrow
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]。
interface IDemoService { public Person get(int id); }
class NormalDemoService implements IDemoService { public Person get(int id) { return new Person(id, "charles`son", 4); } }
<dubbo:application name="rpc-callback-demo" /> <dubbo:registry address="http://10.20.160.198/wiki/display/dubbo/10.20.153.186" /> <bean id="demoService" class="com.alibaba.dubbo.callback.implicit.NormalDemoService" /> <dubbo:service interface="com.alibaba.dubbo.callback.implicit.IDemoService" ref="demoService" version="1.0.0" group="cn"/>
interface Notify { public void onreturn(Person msg, Integer id); public void onthrow(Throwable ex, Integer id); }
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); } }
<bean id ="demoCallback" class = "com.alibaba.dubbo.callback.implicit.NofifyImpl" /> <dubbo:reference id="demoService" interface="com.alibaba.dubbo.callback.implicit.IDemoService" version="1.0.0" group="cn" > <dubbo:method name="get" async="true" onreturn = "demoCallback.onreturn" onthrow="demoCallback.onthrow" /> </dubbo:reference>
callback
与 async
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]:
async=true onreturn="xxx"
async=false onreturn="xxx"
async=true
async=false
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