This version is still in development and is not considered stable yet. For the latest stable version, please use Spring Integration 6.4.0!

IntegrationFlow as a Gateway

The IntegrationFlow can start from the service interface that provides a GatewayProxyFactoryBean component, as the following example shows:

public interface ControlBusGateway {

    void send(String command);
}

...

@Bean
public IntegrationFlow controlBusFlow() {
    return IntegrationFlow.from(ControlBusGateway.class)
            .controlBus()
            .get();
}

All the proxy for interface methods are supplied with the channel to send messages to the next integration component in the IntegrationFlow. You can mark the service interface with the @MessagingGateway annotation and mark the methods with the @Gateway annotations. Nevertheless, the requestChannel is ignored and overridden with that internal channel for the next component in the IntegrationFlow. Otherwise, creating such a configuration by using IntegrationFlow does not make sense.

By default, a GatewayProxyFactoryBean gets a conventional bean name, such as [FLOW_BEAN_NAME.gateway]. You can change that ID by using the @MessagingGateway.name() attribute or the overloaded IntegrationFlow.from(Class<?> serviceInterface, Consumer<GatewayProxySpec> endpointConfigurer) factory method. Also, all the attributes from the @MessagingGateway annotation on the interface are applied to the target GatewayProxyFactoryBean. When annotation configuration is not applicable, the Consumer<GatewayProxySpec> variant can be used for providing appropriate option for the target proxy. This DSL method is available starting with version 5.2.

With Java 8, you can even create an integration gateway with the java.util.function interfaces, as the following example shows:

@Bean
public IntegrationFlow errorRecovererFlow() {
    return IntegrationFlow.from(Function.class, (gateway) -> gateway.beanName("errorRecovererFunction"))
            .<Object>handle((p, h) -> {
                throw new RuntimeException("intentional");
            }, e -> e.advice(retryAdvice()))
            .get();
}

That errorRecovererFlow can be used as follows:

@Autowired
@Qualifier("errorRecovererFunction")
private Function<String, String> errorRecovererFlowGateway;