Example ex09_1: Conneg with JAX-RS

This example is a slight modification from ex06_1 and shows two different concepts. First, the same JAX-RS resource method can process two different media types. Chapter 9 gives the example of a method that returns a JAXB annotated class instance that can be returned as either JSON or XML. We’ve implemented this in ex09_1 by slightly changing the CustomerResource.getCustomer() method:

@Path("/customers")
public class CustomerResource {
...
   @GET
   @Path("{id}")
   @Produces({"application/xml", "application/json"})
   public Customer getCustomer(@PathParam("id") int id)
   {
      ...
   }

The JAXB provider that comes with RESTEasy can convert JAXB objects to JSON or XML. In this example, we have added the media type application/json to getCustomer()’s @Produces annotation. The JAX-RS runtime will process the Accept header and pick the appropriate media type of the response for getCustomer(). If the Accept header is application/xml, XML will be produced. If the Accept header is JSON, the Customer object will be outputted as JSON.

The second concept being highlighted here is that you can use the @Produces annotation to dispatch to different Java methods. To illustrate this, we’ve added the getCustomerString() method, which processes the same URL as getCustomer() but for a different media type:

   @GET
   @Path("{id}")
   @Produces("text/plain")
   public Customer getCustomerString(@PathParam("id") int id)
   {
      return getCustomer(id).toString();
   }

The Client Code

The client code for this example executes various HTTP GET requests to retrieve different representations of a Customer. Each request sets the Accept header a little differently so that it can obtain a different representation. For example:

public class CustomerResourceTest
{
   @Test
   public void testCustomerResource() throws Exception
   {
      ... initialization code ...

      System.out.println("*** GET XML Created Customer **");
      String xml = client.target(location).request()
                                .accept(MediaType.APPLICATION_XML_TYPE)
                                .get(String.class);
      System.out.println(xml);

      System.out.println("*** GET JSON Created Customer **");
      String json = client.target(location).request()
              .accept(MediaType.APPLICATION_JSON_TYPE)
              .get(String.class);
      System.out.println(json);
   }
}

The SyncInvoker.accept() method is used to initialize the Accept header. The client extracts a String from the HTTP response so it can show you the request XML or JSON.

Build and Run the Example Program

Perform the following steps:

1. Open a command prompt or shell terminal and change to the ex09_1 directory of the workbook example code.
2. Make sure your PATH is set up to include both the JDK and Maven, as described in Chapter 17.
3. Perform the build and run the example by typing maven install.