I need a component that:
Receives a message, enacts a transformation on both the payload and header of the message (so far it acts like a transformer).
Then, based on the values passed in on the header route to an appropriate channel (acting like a header-router).
I'd like to configure this purely using annotations in java rather than XML, but I'll absolutely take what I can get in that regard. If someone knows the XML solution please pass it along.
If it helps, my use case is that I want the transformation that the transformer enacts on a message payload to be dependent on a custom loaded header value. I also want the channel that is used to sent the message from the transformer to be dependent on the header value.
I am aware of the solution that involves multiple transformers, one per transformation type as defined in the header value, and then a router. I'm trying to avoid this solution and only use at most a single router and single transformer.
Thank you for your help.
In Spring Integration channels act as any other beans. You could use a service activator to invoke a method on any bean. That bean could have the required channels injected. You could use the @Qualifier annotation to select, which channel should be injected, or just autowire a Map<String, MessageChannel> wich would get indexed by the bean name of the channel. It could pass transformed messages to those channels.
A Spring Boot app:
package demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ImportResource;
import org.springframework.integration.config.EnableIntegration;
@SpringBootApplication
@EnableIntegration
@ImportResource("classpath:int.xml")
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
The gateway interface:
package demo;
public interface MyGateway {
public void send(Object o);
}
The service to be invoked:
package demo;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.integration.support.MessageBuilder;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.stereotype.Service;
@Service
public class MyService {
private final Map<String, MessageChannel> channels;
@Autowired
public MyService(Map<String, MessageChannel> channels) {
super();
this.channels = channels;
}
public void transformAndRoute(Message<?> in) {
// do your business logic here
Message<?> out = MessageBuilder.fromMessage(in).build();
// if(something)...
channels.get("fooChannel").send(out);
}
}
Integration config:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:int="http://www.springframework.org/schema/integration"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/spring-integration.xsd">
<int:gateway id="myGateway" service-interface="demo.MyGateway"
default-request-channel="inChannel" />
<int:service-activator input-channel="inChannel"
ref="myService" method="transformAndRoute" />
<int:channel id="inChannel" />
<int:logging-channel-adapter id="fooChannel" level="INFO" log-full-message="true"/>
</beans>
And finally a simple integration test:
package demo;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=DemoApplication.class)
public class MyGatewayIT {
@Autowired
MyGateway myGateway;
@Test
public void test() {
myGateway.send(new Object());
// do your assertions here
}
}
Output:
14:17:19.733 [main] DEBUG o.s.i.handler.LoggingHandler - org.springframework.integration.handler.LoggingHandler#0 received message: GenericMessage [payload=java.lang.Object@6f2cfcc2, headers={id=6791344c-07b4-d420-0d17-e2344f4bf15b, timestamp=1437826639733}]
BUT
The main benefit of developing message based systems is that you create your application out of small, loosely coupled components that are easy to test, reuse and change. Creating a component that plays two roles in a process brakes that rule. Additionally your code is realy tied to Spring Integration if you create it as above. What you could do instead is create a couple of components that each have a single responsibility, and then configure them to act in a chain.
What you could do is create a transformer that modifies the payload and headers of the message. That transformer would encapsulate your business logic and would set a header (say, myRoutingHeader) that can be later used in routing. It would probably be even better to have a transformer for business logic, and a header enricher for adding the header. But let's assume that you are doing it in a single class. Define that class as a bean (say myTransformer). Then in your config :
<int:channel id="inChannel/>
<!-- if performance is important consider using a SpEL expression to
invoke your method instead as they can be configured to be compiled -->
<int:transformer ref="myTransformer" input-channel="inChannel"
method="transform" output-channel="routingChannel"/>
<int:channel id="routingChannel/>
<int:header-value-router input-channel="routingChannel" header-name="myRoutingHeader">
<int:mapping value="foo" channel="fooChannel" />
<int:mapping value="bar" channel="barChannel" />
</int:header-value-router>