Posts Tagged Java

Today I was amazed to discover that Unit testing JAX-RS resources with JUnit 4 and Java 6 is insanely easy.

Have a look at the example below and then read the description underneath if things are not clear enough already.

import static org.junit.Assert.*;

import java.io.*;
import java.net.*;

import javax.ws.rs.*;

import org.junit.*;

import com.sun.jersey.api.container.httpserver.HttpServerFactory;
import com.sun.net.httpserver.HttpServer;

@Path("/hellotest")
public class MyResourceTest {

    private static final String LOCALHOST = "http://localhost:9998/";

    private static HttpServer server;

    @GET
    @Produces("text/plain")
    public String testSystem(){
        return "Hello. This is a test";
    }

    @BeforeClass
    public static void setUp() throws Exception{
        System.out.println("Creating server");
        server = HttpServerFactory.create(LOCALHOST);

        System.out.println("Starting server");
        server.start();

        System.out.println("HTTP server started");
        System.out.println("Running tests...");

        testResourceAtUrl(new URL(LOCALHOST + "hellotest"));
    }

    private static String testResourceAtUrl(URL url) throws Exception {

        try {
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();

            connection.setRequestMethod("GET");
            connection.connect();

            InputStream inputStream = connection.getInputStream();

            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            String firstLineOfText = reader.readLine();//you can also read the whole thing and then test
            System.out.println("Read: " + firstLineOfText);

            System.out.println("System was initialized correctly. About to run actual tests...");

            connection.disconnect();

            return firstLineOfText;

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        throw new Exception("could not establish connection to " + url.toExternalForm());
    }

    @Test
    public void testMyMethod() throws Exception {
        String activationText = testResourceAtUrl(new URL(LOCALHOST + "myresource"));

        //TODO test here

    }

    /**
    * Destroy the server
    */
    @AfterClass
    public static void tearDown() throws IOException{
        System.out.println("Stopping server");
        server.stop(0);
        System.out.println("Server stopped");
    }

}

So here’s what the code above means:
1. @Path(”/hellotest”) The unit test itself is set up as a resource so when the tests are run we can check that the system is working by consuming the resource defined by testSystem()
2. Java 6 allows us to set up a HTTP server very easily using  HttpServerFactory.create(LOCALHOST) This way we simply go ahead and send HTTP requests without having to worry about 3rd party libs and setting up mock HTTP servers.
3. testResourceAtUrl(new URL(LOCALHOST + “hellotest”)) does the hard work: it requests the resource from the location that we specify in the method call.  
4. put your actual test data in the placeholder

Of course this is a simplified test, and it is meant just to show you how easy it is to test your RESTful webservices. How would you make this better?

Cheers…