This version is still in development and is not considered stable yet. For the latest stable version, please use Spring Integration 6.3.2! |
Operator gateway()
The gateway()
operator in an IntegrationFlow
definition is a special service activator implementation, to call some other endpoint or integration flow via its input channel and wait for reply.
Technically it plays the same role as a nested <gateway>
component in a <chain>
definition (see Calling a Chain from within a Chain) and allows a flow to be cleaner and more straightforward.
Logically, and from business perspective, it is a messaging gateway to allow the distribution and reuse of functionality between different parts of the target integration solution (see Messaging Gateways).
This operator has several overloads for different goals:
-
gateway(String requestChannel)
to send a message to some endpoint’s input channel by its name; -
gateway(MessageChannel requestChannel)
to send a message to some endpoint’s input channel by its direct injection; -
gateway(IntegrationFlow flow)
to send a message to the input channel of the providedIntegrationFlow
.
All of these have a variant with the second Consumer<GatewayEndpointSpec>
argument to configure the target GatewayMessageHandler
and respective AbstractEndpoint
.
Also, the IntegrationFlow
-based methods allows calling existing IntegrationFlow
bean or declare the flow as a sub-flow via an in-place lambda for an IntegrationFlow
functional interface or have it extracted in a private
method cleaner code style:
@Bean
IntegrationFlow someFlow() {
return IntegrationFlow
.from(...)
.gateway(subFlow())
.handle(...)
.get();
}
private static IntegrationFlow subFlow() {
return f -> f
.scatterGather(s -> s.recipientFlow(...),
g -> g.outputProcessor(MessageGroup::getOne))
}
If the downstream flow does not always return a reply, you should set the requestTimeout to 0 to prevent hanging the calling thread indefinitely.
In that case, the flow will end at that point and the thread released for further work.
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