Exit Spring Integration when no more messages

问题

I'm using a Spring Integration (4.1) config to retrieve message from DB as a batch more than as a service. I know I'll have a dozen of messages to process daily, and therefore I need to run the batch once a day.

My jdbc:inbound-channel-adapter is configured to retrieve max-rows-per-poll="1". I'd like to be notified in some way when there are no more messages, so that I can exit the batch, but I have issues finding where to "plug". I tried with an interceptor that remembers when last message went through + a scheduled task that retrieves that timestamp and checks if it's more than a configured timeout, but it felt very cumbersome and tried with AOP instead, which feels like a better solution.

I'd like to intercept the call to AbstractPollingEndpoint.doPoll() which returns false when there's no message but I'm not able to find a way to do that : I tried subclassing AbstractRequestHandlerAdvice but that doesn't work when applied on a poller (it tells me so in the logs). Now I'm trying to implement MethodInterceptor and configure as below, and I see I can intercept the call to "call" method, but I'm not sure it's the right way

<int:poller default="true" trigger="periodicTriggerWithInitialDelay">
    <int:advice-chain>          
        <bean class="com.myBatch.NoMoreMessageNotifierAdvice" />
        <ref bean="txAdvice"/>
    </int:advice-chain>
</int:poller>

Isn't there an easier way to do this ? The main difficulty, as stated here http://forum.spring.io/forum/spring-projects/integration/127410-poller-with-advice-chain , is that at this stage, we don't have message to work on.

Thanks

Vincent

回答1:

Looks like I was very close to the answer actually.. Since I have access to the result of call method, all I need to do is throw exception if result is false, along with XML config from the question :

public class NoMoreMessageNotifierAdvice implements MethodInterceptor {

@Override
public Object invoke(MethodInvocation invocation) throws Throwable {

    Object result=invocation.proceed();

    if(result instanceof Boolean){

        boolean hasPolledAMessage=(Boolean)result;

        if(hasPolledAMessage){
            return true;
        }
        else{
            throw new StopBatchException("no message was received on latest poll -> throwing exception to exit");
        }       
    }

    return result;
}

}

回答2:

The upcoming 4.2 release (we just released the first milestone) has support for conditional pollers.

来源：https://stackoverflow.com/questions/30567742/exit-spring-integration-when-no-more-messages

标签

spring-integration