how to implement integration router in java

Question

i am trying to convert below XML snippet into Java version, appreciate any help here

<int:router input-channel="channel_in" default-output-channel="channel_default" 
  expression="payload.name" ignore-channel-name-resolution-failures="true">
    <int:mapping value="foo" channel="channel_one" />
    <int:mapping value="bar" channel="channel_two" />
</int:router>

Here is what i did for my concrete example

@Router(inputChannel = "routerChannel")
    public String route(Account message) {
        if (message.getType().equals("check")) {
            return "checkChannel";
        } else if (message.getType().equals("credit")) {
            return "creditChannel";
        } 
        return "errorChannel";
}

@Bean
public DirectChannel checkChannel() {
    return new DirectChannel();
}

when i do above i am seeing below error

org.springframework.messaging.MessageDeliveryException: Dispatcher has no subscribers for channel 'application:8090.checkChannel'.;

Artem Bilan · Accepted Answer · 2018-08-27 16:51:50Z

1

All the Spring Integration custom tag has a description like this:

<xsd:element name="router" type="routerType">
    <xsd:annotation>
        <xsd:documentation>
            Defines a Consumer Endpoint for the
            'org.springframework.integration.router.AbstractMessageProcessingRouter' implementation
            that serves as an adapter for invoking a method on any
            Spring-managed object as specified by the "ref" and "method" attributes.
        </xsd:documentation>
    </xsd:annotation>
</xsd:element>

So, it becomes pretty clear that we need some AbstractMessageProcessingRouter implementation to be present in the Java Configuration.

Also we have a paragraph in the Reference Manual like this:

With XML configuration and Spring Integration Namespace support, the XML Parsers hide how target beans are declared and wired together. For Java & Annotation Configuration, it is important to understand the Framework API for target end-user applications.

According your expression="payload.name" we need to look for the ExpressionEvaluatingRouter and then also read a chapter about @Bean configuration:

    @Bean
    @Router(inputChannel = "channel_in")
    public ExpressionEvaluatingRouter expressionRouter() {
        ExpressionEvaluatingRouter router = new ExpressionEvaluatingRouter("payload.name");
        router.setDefaultOutputChannelName("channel_default");
        router.setChannelMapping("foo", "channel_one");
        router.setChannelMapping("bar", "channel_two");
        return router;
    }

answered Aug 27, 2018 at 16:51

Artem Bilan

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5 Comments

user10270958 Over a year ago

thank you, how do i handle this router based on an attribute value of an object, i have a Account object in which based on the type of object i should be able to route it to respective channels, also how do i define DirectChannel using java

Artem Bilan Over a year ago

Well, you still continue to use the SpEL against that Account payload. The DirectChannel has to be declared as a @Bean. Please, bear in mind that Spring Integration is just a Spring Framework extension for EIP, but it is still Spring, therefore everything is a bean and you should follow existing Java & Annotation rules to declare Spring Integration components.

Artem Bilan Over a year ago

Good, but do you really have a @EnableIntegration on some @Configuration class? docs.spring.io/spring-integration/docs/current/reference/html/…

Artem Bilan Over a year ago

Good. So, you route a check message to the checkChannel, but is there anything who consumes this channel, e.g. @ServiceActivator? Maybe it's time for you to come back to documentation to understand how Spring Integration works?

user10270958 Over a year ago

yes i have that but there was a spell issue on the Service Activator channel definition, any ways thanks for guiding me

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