basic REST service in Apache CXF vs. Camel-CXF

This article demonstrates how to create/test a basic REST service in CXF vs. Camel-CXF. Given the range of configuration and deployment options, I'm focusing on building a basic OSGi bundle that can be deployed in Fuse 4.2 (ServiceMix)...basic knowledge of Maven, ServiceMix and Camel are assumed.

Apache CXF

For more details, see http://cxf.apache.org/docs/jax-rs.html.

Here is an overview of the steps to get a basic example running...

1. add dependencies to your pom.xml

   <dependency>
      <groupId>org.apache.cxf</groupId>
      <artifactId>cxf-rt-frontend-jaxrs</artifactId>
      <version>2.3.0</version>
   </dependency>

2. setup the bundle-context.xml file

    <import resource="classpath:META-INF/cxf/cxf.xml" />
    <import resource="classpath:META-INF/cxf/cxf-extension-jaxrs-binding.xml" />
    <import resource="classpath:META-INF/cxf/cxf-extension-http.xml" />
    <import resource="classpath:META-INF/cxf/cxf-extension-http-jetty.xml" />

    <bean id="exampleBean" class="com.example.ExampleBean" />

    <jaxrs:server id="exampleService" address="http://localhost:9000/">
        <jaxrs:serviceBeans>
            <ref bean="exampleBean" />
        </jaxrs:serviceBeans>
    </jaxrs:server>

3. create a service bean class

@Path("/example")
public class ExampleBean {

    @GET
    @Path("/")
    public String ping() throws Exception {
        return "SUCCESS";
    }
}

4. deploy and test

  build the bundle using "mvn install"
  start servicemix
  deploy the bundle
  open a browser to "http://localhost:9000/example" (should see "SUCCESS")

Camel-CXF

For details, see http://camel.apache.org/cxfrs.html. 

Here is an overview of the steps to get a basic example running...

1. add dependencies to your pom.xml

        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-core</artifactId>
            <version>${camel.version}</version>
        </dependency>

        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-cxf</artifactId>
            <version>${camel.version}</version>
        </dependency>  

2. setup the bundle-context.xml file

    <camelContext trace="true" id="camelContext" xmlns="http://camel.apache.org/schema/spring">
        <package>com.example</package>
    </camelContext>

3. create a RouteBuilder class

public class ExampleRouter extends RouteBuilder {

    @Override
    public void configure() throws Exception {

        from("cxfrs://http://localhost:9000?resourceClasses=" + ExampleResource.class.getName())
            .process(new Processor() {
                public void process(Exchange exchange) throws Exception {
                    //custom processing here
                }
            })
            .setBody(constant("SUCCESS"));
        }
    }

4. create a REST Resource class

@Path("/example")
public class ExampleResource {

    @GET
    public void ping() {
        //strangely, this method is not called, only serves to configure the endpoint
    }
}

5.  deploy and test

  build bundle using "mvn install"
  start servicemix
  deploy the bundle
  open a browser to "http://localhost:9000/example" (should see "SUCCESS")

Unit Testing

To perform basic unit testing for either of these approaches, use the Apache HttpClient APIs by first adding this dependency to your pom.xml...

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>

            <artifactId>httpclient</artifactId>
            <version>4.0.1</version>
        </dependency>

Then, you can use these APIs to create a basic test to validate the REST services created above...

        String url = "http://localhost:9000/example";
        HttpGet httpGet = new HttpGet(url);
        HttpClient httpclient = new DefaultHttpClient();
        HttpResponse response = httpclient.execute(httpGet);
        String responseMessage = EntityUtils.toString(response.getEntity());

        assertEquals("SUCCESS", responseMessage);
        assertEquals(200, response.getStatusLine().getStatusCode());

Summary

Overall, the approaches are very similar, but you can use various combinations of Spring XML and Java APIs to set this up.  I focused on a common approach to demonstrate the basics of each approach side-by-side.

That being said, if you have requirements for complex REST services (security, interceptors, filters, etc), I recommend grabbing a copy of Apache CXF Web Service Development and following some of the more complex examples on the Apache CXF, Camel-CXFRS pages.

In practice, I've generally used Camel-CXF because it gives you the flexibility of integrating with other Camel components and allows you to leverage the rich routing features of Camel.  I hope to cover more complex scenarios in future posts...