TOTD #57: Jersey Client API - simple and easy to use

href="http://blogs.sun.com/arungupta/entry/totd_56_simple_restful_web">TOTD
#56 explains how to create a RESTful Web service endpoint
using Jersey
and publish the resource using JSON representation. The blog entry
showed how the endpoint can be accessed from a Web browser. This style="font-weight: bold;">Tip style="font-weight: bold;">Of style="font-weight: bold;">The style="font-weight: bold;">Day explains how to
use Jersey
Client APIs to invoke the published endpoint.



Lets get started!

1. Create a new directory
   "./src/test/java/org/glassfish/samples"
2. Add a test
1. Add a template test file "AppTest.java" as shown below:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   package org.glassfish.samples;
   
   
   
   import junit.framework.Test;
   
   import junit.framework.TestCase;
   
   import junit.framework.TestSuite;
   
   
   
   /**
   
    * Unit test for simple App.
   
    */
   
   public class AppTest
   
       extends TestCase
   
   {
   
       /**
   
        * Create the test case
   
        *
   
        * @param testName name of the
   test case
   
        */
   
       public AppTest( String testName )
   
       {
   
          
   super( testName );
   
       }
   
   
   
       /**
   
        * @return the suite of tests
   being tested
   
        */
   
       public static Test suite()
   
       {
   
          
   return new TestSuite( AppTest.class );
   
       }
   
   
   
       /**
   
        * Rigourous Test :-)
   
        */
   
       public void testApp()
   
       {
   
           assertTrue(true);
   
       }
   
   }
2. Add a new method "createResource()" as:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
       private
   WebResource createResource() {
   
          
   Client client = Client.create();
   
          
   WebResource resource =
   client.resource("http://localhost:8080/helloworld-webapp/webresources/myresource");
   
          
   return resource;
   
       }

   
   
   This code creates a default instance of Jersey Client and creates a Web
   resource from that client for the URI passed as an argument.

3. Change the implementation of "testApp()" method as:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
          
   Greeting result = createResource().get(Greeting.class);
   
          
   assertTrue(result.greeting.equals("Hi there!"));

   
   
   This invokes the
   GET method on the resource by passing specific type and compares the
   returned and expected value.
   

4. Add the following "imports":
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   import com.sun.jersey.api.client.Client;
   
   import com.sun.jersey.api.client.WebResource;
   
5. Copy "Greeting.java" from TOTD #56
   to "./src/test/java/org/glassfish/samples"
   directory.
3. Run the test
1. Deploy the endpoint as "mvn glassfish:run".
2. Run the test as "mvn test". The following output is shown:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   ~/samples/jersey/helloworld-webapp > style="font-weight: bold;">mvn test
   
   [INFO] Scanning for projects...
   
   [INFO]
   ------------------------------------------------------------------------
   
   [INFO] Building helloworld-webapp Jersey Webapp
   
   [INFO]    task-segment: [test]
   
   [INFO]
   ------------------------------------------------------------------------
   
   [INFO] [resources:resources]
   
   [INFO] Using default encoding to copy filtered resources.
   
   [INFO] [compiler:compile]
   
   [INFO] Nothing to compile - all classes are up to date
   
   [INFO] [resources:testResources]
   
   [INFO] Using default encoding to copy filtered resources.
   
   [INFO] [compiler:testCompile]
   
   [INFO] Compiling 1 source file to
   /Users/arungupta/samples/jersey/helloworld-webapp/target/test-classes
   
   [INFO] [surefire:test]
   
   [INFO] Surefire report directory:
   /Users/arungupta/samples/jersey/helloworld-webapp/target/surefire-reports
   
   
   
   -------------------------------------------------------
   
    T E S T S
   
   -------------------------------------------------------
   
   Running org.glassfish.samples.AppTest
   
   Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.587
   sec
   
   
   
   Results :
   
   
   
   Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
   
   
   
   [INFO]
   ------------------------------------------------------------------------
   
   [INFO] BUILD SUCCESSFUL
   
   [INFO]
   ------------------------------------------------------------------------
   
   [INFO] Total time: 4 seconds
   
   [INFO] Finished at: Mon Nov 24 16:50:17 PST 2008
   
   [INFO] Final Memory: 18M/43M
   
   [INFO]
   ------------------------------------------------------------------------
4. View request and response messages
1. Change the implementation of "createResource()" method as
   (changes highlighted in bold):
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
          
   Client client = Client.create();
   
          
   WebResource resource =
   client.resource("http://localhost:8080/helloworld-webapp/webresources/myresource");
   
           style="font-weight: bold;">resource.addFilter(new
   LoggingFilter());
   
          
   return resource;
2. Running the tests as "mvn test" now shows the output,
   with request and response messages, as shown below:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   Running org.glassfish.samples.AppTest
   
   1 * Out-bound request
   
   1 > GET
   http://localhost:8080/helloworld-webapp/webresources/myresource
   
   1 >
   
   1 < 200
   
   1 < X-Powered-By: Servlet/2.5
   
   1 < Transfer-Encoding: chunked
   
   1 < Content-Type: application/json
   
   1 < Server: GlassFish/v3
   
   1 < Date: Tue, 25 Nov 2008 07:07:51 GMT
   
   1 <
   
   {"greeting":"Hi there!"}
   
   1 * In-bound response
   
   Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 1.074
   sec

Really easy!



Even though the APIs are used to invoke a RESTful endpoint deployed
using Jersey but are very generic and can be used to invoke any RESTful
endpoint. href="http://blogs.sun.com/sandoz/entry/jersey_client_api">Paul's
blog explain in detail on the usage. You can also see how
these APIs can be used to href="http://blog.beuchelt.org/2008/07/18/Using+Abdera+And+The+Jersey+Client+API.aspx">consume
a service hosted using Apache Abdera.



href="https://jersey.dev.java.net/source/browse/*checkout*/jersey/tags/jersey-1.0/api/jersey/com/sun/jersey/api/client/package-frame.html">com.sun.jersey.api.client,
href="https://jersey.dev.java.net/source/browse/*checkout*/jersey/tags/jersey-1.0/api/jersey/com/sun/jersey/api/client/config/package-frame.html">com.sun.jersey.api.client.config,
and href="https://jersey.dev.java.net/source/browse/*checkout*/jersey/tags/jersey-1.0/api/jersey/com/sun/jersey/api/client/filter/package-frame.html">com.sun.jersey.api.client.filter
packages documents all the classes that provide support for client-side
communication with HTTP-based RESTful Web services.



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