Before calling, after calling, and when an exception occurs, three events oninvoke, onreturn, and onthrow will be triggered. You can configure which method of which class to notify when an event occurs.
https://github.com/apache/dubbo-samples/tree/master/dubbo-samples-notify
Before calling the service method, we can record the start time, and after the call ends, we can count the entire call cost. When an exception occurs, we can warn or print error logs, or record request logs and response logs before and after calling the service.
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="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"/>
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);
}
}
There are the following combinations of the two:
async=true onreturn="xxx"async=false onreturn="xxx"async=trueasync=falsecallback and async function are decomposed orthogonally, async=true indicates whether the result is returned immediately, async=false is the default, onreturn indicates whether a callback is required.
<bean id="demoCallback" class = "org.apache.dubbo.callback.implicit.NotifyImpl" />
<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>
IDemoService demoService = (IDemoService) context. getBean("demoService");
NotifyImpl notify = (NotifyImpl) context. getBean("demoCallback");
int requestId = 2;
Person ret = demoService. get(requestId);
Assert.assertEquals(null, ret);
//for Test: It is only used to illustrate that the callback is called normally, and the specific implementation of the business is determined by itself.
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());