如何中断或取消Spring Integration Java DSL流？

Question

Contemplating implementation of a feature wherein a JdbcRepositoryHandler (implemnting MessageHandler ) might listen for an outside event (eg, CancelRunEvent ).

I think I'd use Spring' ApplicationEvent support to publish an event via a REST controller endpoint. And I would guess I'd have the aforementioned handler implement ApplicationListener to listen for a particular event?

The question is: if the handler is saturated with messages it needs to process, how would I signal termination of all subsequent messages that may have emanated upstream eg, from a FileSplitter ?

While I could easily construct a condition to be checked before calling a method responsible eg, for a persistence operation (based on some state received from the CancelRunEvent ), how could I interrupt the flow entirely ?

For illustrative purposes, imagine a flow like:

@Bean
protected IntegrationFlow s3ChannelFlow() {
    // @see http://docs.spring.io/spring-integration/reference/html/files.html#file-reading
    // @formatter:off
    return IntegrationFlows
        .from(s3Channel())
        .enrichHeaders(h -> h.headerFunction(RunStats.FILE_TOKEN, f -> UUID.randomUUID().toString()))
        .channel(runStatsChannel())
        .transform(new FileToInputStreamTransformer())
        .split(new FileSplitter())
        .transform(new JsonToObjectViaTypeHeaderTransformer(new Jackson2JsonObjectMapper(objectMapper), typeSupport))
        .publishSubscribeChannel(p -> p.subscribe(persistenceSubFlow()))
        .get();
    // @formatter:on
}

@Bean
protected IntegrationFlow persistenceSubFlow() {
    // @formatter:off
    return f -> f
            // @see http://docs.spring.io/spring-integration/reference/html/messaging-routing-chapter.html#agg-and-group-to
            .aggregate(a -> a
                    .correlationStrategy(new HeaderAttributeCorrelationStrategy(RunStats.FILE_TOKEN))
                    .releaseStrategy(new MessageCountReleaseStrategy(persistenceBatchSize))
                    .sendPartialResultOnExpiry(true)
                    .expireGroupsUponCompletion(true)
                    .groupTimeoutExpression(persistenceBatchReleaseTimeoutMillis)
            )
            .handle(new JdbcRepositoryHandler(typeSupport, metricRegistry, runStatsRepository));
    // @formatter:on
}

Answer 1

It's not entirely clear what you mean or why you would need the JdbcRepositoryHandler to manage this rather than some other ApplicationListener .

Your flow is running on some thread upstream of s3Channel() . Depending on what that is, you could stop() the message source and no new messages will be emitted after the current one (or ones if it's multi-threaded).

However, you may (likely will) end up with a partial aggregation sitting in memory until the group times out.