JAX-RS - Accessing WADL (Web Application Description Language)

WADL (Web Application Description Language) is an XML document, which describes what resources of an application can be accessed by a client. WADL is considered as the REST equivalent of SOAP's WSDL.

Let's see an example how to access WADL in a JAX-RS application.

Example

Let's create multiple resource methods:

@Path("/")
public class MyResource {

  @Path("/test")
  @GET
  public Response handle() {
      Response r = Response.ok("test with GET, body content")
                           .build();
      return r;
  }
    .............
  @Path("/test2")
  @GET
  public Response handle2() {
      Response r = Response.ok("test2 with GET, body content")
                           .build();
      return r;
  }
    .............
  @Path("/test3")
  @GET
  public Response handle5() {
      Response r = Response.ok("test3 with GET, body content")
                           .build();
      return r;
  }
    .............
  @Path("/test4")
  @DELETE
  public Response handle7() {
      Response r = Response.ok("test4 with DELETE, body content")
                           .build();
      return r;
  }
    .............
}

mvn tomcat7:run-war

JAX-RS client

WADL can be retrieved from URI application.wadl as shown in this example.

public class MyClient {
  public static void main(String[] args) {
      Client client = ClientBuilder.newClient();
      WebTarget target =
              client.target("http://localhost:8080/application.wadl" );
      Response response = target.request()
                                .get();
      System.out.printf("status: %s%n", response.getStatus());

      MultivaluedMap<String, Object> headers = response.getHeaders();
      System.out.println("-- response headers --");
      headers.entrySet().forEach(e-> System.out.printf("%s: %s%n", e.getKey(), e.getValue()));
      System.out.printf("-- response body --%n%s%n", response.readEntity(String.class));
  }
}

Output

status: 200
-- response headers --
Last-modified: [Thu, 08 Jun 2017 16:15:01 CDT]
Server: [Apache-Coyote/1.1]
Content-Length: [2431]
Date: [Thu, 08 Jun 2017 21:15:43 GMT]
Content-Type: [application/vnd.sun.wadl+xml]
-- response body --
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<application xmlns="http://wadl.dev.java.net/2009/02">
    <doc xmlns:jersey="http://jersey.java.net/" jersey:generatedBy="Jersey: 2.25.1 2017-01-19 16:23:50"/>
    <doc xmlns:jersey="http://jersey.java.net/" jersey:hint="This is simplified WADL with user and core resources only. To get full WADL with extended resources use the query parameter detail. Link: http://localhost:8080/application.wadl?detail=true"/>
    <grammars/>
    <resources base="http://localhost:8080/">
        <resource path="/">
            <resource path="/test">
                <method id="handle" name="GET">
                    <response>
                        <representation mediaType="*/*"/>
                    </response>
                </method>
            </resource>
            <resource path="/test3">
                <method id="handle5" name="GET">
                    <response>
                        <representation mediaType="*/*"/>
                    </response>
                </method>
                <method id="handle6" name="OPTIONS">
                    <response>
                        <representation mediaType="*/*"/>
                    </response>
                </method>
            </resource>
            <resource path="/test2">
                <method id="handle2" name="GET">
                    <response>
                        <representation mediaType="*/*"/>
                    </response>
                </method>
                <method id="handle3" name="POST">
                    <response>
                        <representation mediaType="*/*"/>
                    </response>
                </method>
                <method id="handle4" name="HEAD">
                    <response>
                        <representation mediaType="*/*"/>
                    </response>
                </method>
            </resource>
            <resource path="/test4">
                <method id="handle8" name="PUT">
                    <response>
                        <representation mediaType="*/*"/>
                    </response>
                </method>
                <method id="handle7" name="DELETE">
                    <response>
                        <representation mediaType="*/*"/>
                    </response>
                </method>
            </resource>
        </resource>
    </resources>
</application>

Since WADL can be accessed via a simple GET request, we can also access it in a web browser.

Example Project

Dependencies and Technologies Used:

• jersey-server 2.25.1: Jersey core server implementation.
• jersey-container-servlet 2.25.1: Jersey core Servlet 3.x implementation.
• JDK 1.8
• Maven 3.3.9