How to call subflows after aggregate() method in scatter-gather pattern in Spring Integration

Question

Here I'm using scatter gather pattern. If I want to call another IntegrationFlow after aggregate() and before to(), how do I do that? can I use recipientFlow here so that I can make that flow conditional as well?

     @Bean
          public IntegrationFlow flow() {
            return flow ->
                flow.handle(validatorService, "validateRequest")
                    .split()
                    .channel(c -> c.executor(Executors.newCachedThreadPool()))
                    .scatterGather(
                        scatterer ->
                            scatterer
                                .applySequence(true)
                                .recipientFlow(flow1())
                                .recipientFlow(flow2())
                                .recipientFlow(flow3()),
                        gatherer ->
                            gatherer
                                .releaseLockBeforeSend(true)
                                .releaseStrategy(group -> group.size() == 2))
                    .aggregate(lionService.someMethod())
    // here I want to call other Integration flows
                    .gateway(someFlow())
                    .to(someFlow2());
          }

 @Bean
  public IntegrationFlow flow1() {
    return flow ->
        flow.channel(c -> c.executor(Executors.newCachedThreadPool()))
            .enrichHeaders(h -> h.errorChannel("flow1ErrorChannel", true))
            .handle(cdRequestService, "prepareCDRequestFromLoanRequest");
  }
//same way I have flow2 and flow3, and I have set an custom error channel header for all the flows
 @Bean
  public IntegrationFlow someFlow() {
    return flow ->
        flow.filter("headers.sourceSystemCode.equals("001")").channel(c -> c.executor(Executors.newCachedThreadPool()))
            .enrichHeaders(h -> h.errorChannel("someFlow1ErrorChannel", true))
            .handle( Http.outboundGateway("http://localhost:4444/test2")
                .httpMethod(HttpMethod.POST)
                .expectedResponseType(String.class)).bridge();
  }

Till now whenever any error occurred in any of the flow it goes through the custom error channels that have been assigned to them then I process the error but when I have used someFlow1() in .gateway(someFlow()) then the error occurring in that flow is not going to the assigned error channel. How to resolve that?

Inside errorhandler class I'm doing something like below --

//errorhandlerclass

 @ServiceActivator(inputChannel = "flow1ErrorChannel")
  public Message<?> processDBError(MessagingException payload) {
    logger.atSevere().withStackTrace(StackSize.FULL).withCause(payload).log(
        Objects.requireNonNull(payload.getFailedMessage()).toString());
    MessageHeaders messageHeaders = Objects.requireNonNull(payload.getFailedMessage()).getHeaders();
    return MessageBuilder.withPayload(
            new LionException(ErrorCode.DATABASE_ERROR.getErrorData()))
        .setHeader(MessageHeaders.REPLY_CHANNEL, messageHeaders.get("originalErrorChannel"))
        .build();
  }

 @ServiceActivator(inputChannel = "someFlow1ErrorChannel")
  public Message<?> processDBError(MessagingException payload) {
    logger.atSevere().withStackTrace(StackSize.FULL).withCause(payload).log(
        Objects.requireNonNull(payload.getFailedMessage()).toString());
    MessageHeaders messageHeaders = Objects.requireNonNull(payload.getFailedMessage()).getHeaders();
    return MessageBuilder.withPayload(
            new LionException(ErrorCode.CUSTOM_ERROR.getErrorData()))
        .setHeader(MessageHeaders.REPLY_CHANNEL, messageHeaders.get("originalErrorChannel"))
        .build();
  }

Again, if there's any error in someFlow() then error is shown but I want it to go to that method where I'm processing the error as per my requirement.

Also, you can see I've used filter in someFlow() so when the filter expression evaluates true then no problem but when it become false then it's throwing error but I want it to escape and go to next i.e.,.to(someFlow2()). I've used .bridge() by thinking that it'll return to previous context but that's not happening. I know there's some gap in my understanding. Kindly help with the above two problems.

score 0 · Accepted Answer · answered Aug 13 '22 at 00:43

0

To call another flow and come back to the main one you can use a gateway(). But that flow has to return in the end. There is no something like conditional flow: you may send to the channel (next endpoint in the flow) or not via filter() endpoint (or operator if you wish). The to() operator is terminal in the current flow, but you continue your logic in that destination flow whatever you want. Looks like you need to dedicate some of your time to understand what is a message channel and how it connects endpoints in Spring Integration. The IntegrationFlow is just logical container to express a business task - at runtime it is all endpoints and channels between them.

answered Aug 13 '22 at 00:43

Artem Bilan

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Actually in recipient flow we can write expressions which will farther determine whether to execute that flow or not so was curious to know if we have something in to() or gateway() or not. But by your suggestion I understood that I should use filter() for those two. – Somnath Mukherjee Aug 13 '22 at 17:00
Hi @Artem, I've used gateway() as u suggested. And updated the question as I'm getting two issues. Could you pls shine some light on those two issues ? – Somnath Mukherjee Aug 13 '22 at 17:33
Well, the scatter-gather is not related to the question and a bit misleading . The error handling is also out if scope. That’s not how StackOverflow works . I suggested to you in other place to read the doc about the filter: it does not throw an exception by default. You can use `bridge()` in the `rejectFlow()` if you want to bring context back to the main flow. – Artem Bilan Aug 13 '22 at 21:55
.gateway(someFlow(), f -> f.errorChannel("someFlowErrorChannel")) - This worked. – Somnath Mukherjee Aug 14 '22 at 07:31
flow.filter( conditionToCallThisService, f -> f.discardFlow(BaseIntegrationFlowDefinition::bridge)) - This worked. – Somnath Mukherjee Aug 14 '22 at 07:32
Are these fine? – Somnath Mukherjee Aug 14 '22 at 07:32
1

Yep! That looks like what you have asked – Artem Bilan Aug 14 '22 at 11:45

How to call subflows after aggregate() method in scatter-gather pattern in Spring Integration

1 Answers1