Message Routers

Spring Integration natively provides specialized router types, including:

  • HeaderValueRouter

  • PayloadTypeRouter

  • ExceptionTypeRouter

  • RecipientListRouter

  • XPathRouter

As with many other DSL IntegrationFlowBuilder EIP methods, the route() method can apply any AbstractMessageRouter implementation or, for convenience, a String as a SpEL expression or a ref-method pair. In addition, you can configure route() with a lambda and use a lambda for a Consumer<RouterSpec<MethodInvokingRouter>>. The fluent API also provides AbstractMappingMessageRouter options such as channelMapping(String key, String channelName) pairs, as the following example shows:

@Bean
public IntegrationFlow routeFlowByLambda() {
    return IntegrationFlow.from("routerInput")
            .<Integer, Boolean>route(p -> p % 2 == 0,
                    m -> m.suffix("Channel")
                            .channelMapping(true, "even")
                            .channelMapping(false, "odd")
            )
            .get();
}

The following example shows a simple expression-based router:

@Bean
public IntegrationFlow routeFlowByExpression() {
    return IntegrationFlow.from("routerInput")
            .route("headers['destChannel']")
            .get();
}

The routeToRecipients() method takes a Consumer<RecipientListRouterSpec>, as the following example shows:

@Bean
public IntegrationFlow recipientListFlow() {
    return IntegrationFlow.from("recipientListInput")
            .<String, String>transform(p -> p.replaceFirst("Payload", ""))
            .routeToRecipients(r -> r
                    .recipient("thing1-channel", "'thing1' == payload")
                    .recipientMessageSelector("thing2-channel", m ->
                            m.getHeaders().containsKey("recipient")
                                    && (boolean) m.getHeaders().get("recipient"))
                    .recipientFlow("'thing1' == payload or 'thing2' == payload or 'thing3' == payload",
                            f -> f.<String, String>transform(String::toUpperCase)
                                    .channel(c -> c.queue("recipientListSubFlow1Result")))
                    .recipientFlow((String p) -> p.startsWith("thing3"),
                            f -> f.transform("Hello "::concat)
                                    .channel(c -> c.queue("recipientListSubFlow2Result")))
                    .recipientFlow(new FunctionExpression<Message<?>>(m ->
                                    "thing3".equals(m.getPayload())),
                            f -> f.channel(c -> c.queue("recipientListSubFlow3Result")))
                    .defaultOutputToParentFlow())
            .get();
}

The .defaultOutputToParentFlow() of the .routeToRecipients() definition lets you set the router’s defaultOutput as a gateway to continue a process for the unmatched messages in the main flow.

Also see Lambdas And Message<?> Arguments.