camel dynamic router EIP

Camel With Dynamic Router EIP with simple steps.


In this tutorial we learn about dynamic router EIP in camel.In dynamic router EIP , route is defined dynamically.Difference between routing slip and dynamic router is in routing slip we compute the slip up front while in dynamic router we compute route on the fly.Dynamic router can understand more with an example.So let us start

Example

In our example we will send a message to queue and will call a bean where based on logic we will decide route where message will undergo..From test case we will validate our output.So let us start

  • In eclipse go to MyFirstCamelProject that we created in earlier page and right click on src/main/java to create package.New -> package



  • Give any name for example com.preparationforinterview and click on Finish



  • Right click on package and create a java class for example MyRoute.



  • Add following dependency in pom.xml file.you can use any latest version.

  •  	
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    	<modelVersion>4.0.0</modelVersion>
    	<groupId>MyFirstCamelProject</groupId>
    	<artifactId>MyFirstCamelProject</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    	<dependencies>
    		<dependency>
    			<groupId>org.apache.camel</groupId>
    			<artifactId>camel-test</artifactId>
    			<version>2.5.0</version>
    			<scope>test</scope>
    		</dependency>
    		<dependency>
    			<groupId>junit</groupId>
    			<artifactId>junit</artifactId>
    			<version>4.8.1</version>
    			<scope>test</scope>
    		</dependency>
    	</dependencies>
    </project>
    
  • Run mvn:install from command prompt or if you are using Eclipse right click on pom.xml and run mvn install.It will download camel jars

  • Copy below code in MyRoute.

  •  	
    package com.preparationforinterview;
    
    import org.apache.camel.builder.RouteBuilder;
    
    public class MyRoute extends RouteBuilder {
    
    	@Override
    	public void configure() throws Exception {
    		from("direct:start").log("Sending ")
    				.dynamicRouter(bean(MyDynamicRouterBean.class, "route"))
    				.to("mock:result");
    
    	}
    
    }
    

    Explain

    To create a route in camel we need to extend RouteBuilder class and override configure method.In configure method we define our route.In above route we are accepting message from in memory route and logging it to see the content of the message.After that we are calling dynamicRouter where we have passed a bean MyDynamicRouterBean .When bean route method is invoked then camel invokes this method until it gets end of route .End of route it gets by null.

  • Right click on package and create one more java class for example MyDynamicRouterBean.



  • Copy below code in MyDynamicRouterBean.

  •  	
    package com.preparationforinterview;
    
    import org.apache.camel.Exchange;
    import org.apache.camel.Header;
    
    public class MyDynamicRouterBean {
    	public String route(String body,
    			@Header(Exchange.SLIP_ENDPOINT) String previousRouter) {
    		return nextRoute(body, previousRouter);
    	}
    
    	private String nextRoute(String body, String previousRouter) {
    		String message = "I have prepared from preparationforinterview.com"; 
    		if (previousRouter == null) {
    			return "mock://a";
    		} else if ("mock://b".equals(previousRouter)) {
    			return "language://simple:" + message;
    		} else if ("mock://a".equals(previousRouter)) {
    			return "mock://b";
    		} else {
    			return null;
    		}
    	}
    }
    

    Explain

    In above bean we have route method which will be invoked by camel and will continue invoke it until camel gets end of route.

    To test above dynamic route we will create one class DynamicRouteTest.java.



  • At the end we will have following structure


  • Copy below code in DynamicRouteTest.java.

  •  	
    package com.preparationforinterview;
    
    import org.apache.camel.builder.RouteBuilder;
    import org.apache.camel.test.junit4.CamelTestSupport;
    import org.junit.Test;
    
    public class DynamicRouteTest extends CamelTestSupport {
    	@Override
    	protected RouteBuilder createRouteBuilder() throws Exception {
    		return new MyRoute();
    	}
    
    	@Test
    	public void testSplitterEIP() throws Exception {
    		
    	 String output = "Hello, I am preparaing from PreparationforInterview.com";
    	 String message = "I have prepared from preparationforinterview.com"; 
    
    		getMockEndpoint("mock:result").expectedMessageCount(1);
    		
    		getMockEndpoint("mock:result").expectedBodiesReceived(message);
    
    		template.sendBody("direct:start",output);
    		assertMockEndpointsSatisfied();
    
    	}
    }
    

    Explain

    To get camel test kit advantage we need to extend CamelTestSupport.CamelTestSupport class is wrapped on Junit.When we extend CamelTestSupport then we need to override one method createRouteBuilder.In that method create an object of route class.In our case we have done MyRoute.To test router we created method annotated with @Test. In that method we are getting mock endpoint and we have set expectation for example Expected expectedBodiesReceived and expectedMessageCount.After expectation has been set,we are sending message to direct:start queue.To Test execution with our result we fire assertion.template, we get from CamelTestSupport.

    To check the output right click on DynamicRouteTest.java and run it.It will pass test case and we will get following output.


    To run the program from command prompt,open command prompt and go to project location and run below command.
    mvn compile exec:java -Dexec.mainClass=com.preparationforinterview.DynamicRouteTest

Download source code

Camel With Dynamic Route EIP



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