Servlet Sample


	Servlet Sample Application

J2EEUnit provides a sample application that shows how to write test cases for unit testing servlet methods. You should have a look at this sample application as it gives thorough example. However, this section only focuses on explaining the principle by showing a very simple example.

For the sake of simplicity let's imagine we have a servlet called SimpleServlet which has a single method :

registerUser() : Gets the user name from a HTTP request parameter, save it in the HTTP Session and send a Cookie back to the client with the user name in it. The returned HTML prints the name that was retrieved from the HTTP request's parameter.


	Step 1 : The SimpleServlet's code

Here is the code to unit test :

package sample;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class SimpleServlet extends HttpServlet
{
    public void doGet(HttpServletRequest theRequest, HttpServletResponse theResponse) throws IOException
    {
        PrintWriter pw = theResponse.getWriter();

        theResponse.setContentType("text/html");

        pw.print("<html><head/><body>");
        pw.print("<h1>Your name is " + registerUser(theRequest, theResponse) + "</h1>");
        pw.print("</body></html>");
    }

    public String registerUser(HttpServletRequest theRequest, HttpServletResponse theResponse)
    {
        // Get the user name from the HTTP request's parameter
        String name = theRequest.getParameter("USER_NAME");

        // Save it in the session
        HttpSession session = theRequest.getSession();
        session.putValue("NAME", name);

        // And return a cookie
        Cookie cookie = new Cookie("ID", name);
        theResponse.addCookie(cookie);

        return name;
    }
}


	Step 2 : Unit testing strategy

Notice that we mentionned we were going to test the registerUser() method but nothing was said about the doGet() method ... Indeed, unit testing the doGet() (or doPost()) is not completely relevant. This kind of test is actually more a functional test (you can use a framework such as HttpUnit for doing this). However, for some simple cases it is not always easy to differentiate between unit test and functional test, you might want the test to be part of your unit test suite or it is a simple case that do not need to set up a functional test framework. For these cases, J2EEUnit support asserting the output stream returned from your servlet, so it is possible to unit test the doGet() type methods, as demonstrated below.

However, you should try to not put any logic in your doGet and doPost() methods. You should rather delegate any code logic to other methods (such as the registerUser() method is the sample below). It is called the facade pattern. If you do it this way, you can easily unit test your logic code methods one by one.


	Step 3 : The test code

public class TestSimpleServlet extends ServletTestCase
{
[standard JUnit code. See the using section]

    /**
     * Sets the HTTP request parameter that will be available in the test
     * method.
     */
    public void beginRegisterUser(ServletTestRequest theRequest)
    {
        theRequest.addParameter("USER_NAME", "Vincent");
    }

    /**
     * Unit test the registerUSer method.
     */
    public void testRegisterUser()
    {
        // Instantiate the class to test
        SimpleServlet servlet = new SimpleServlet();

        // Call the method to test
        String name = servlet.registerUser(request, response);

        // Verify that it returns the correct name
        assertEquals("Vincent", name);

        // Verify that the name has been put in the session
        assertEquals("Vincent", (String)session.getValue("NAME"));
    }

    /**
     * Verify that a cookie has been returned
     */
    public void endRegisterUser(HttpURLConnection theConnection)
    {
        Hashtable cookies = AssertUtils.getCookies(theConnection);

        Vector list = (Vector)cookies.get("ID");
        assert(list.size() == 1);

        ClientCookie cookie = (ClientCookie)list.elementAt(0);
        assertEquals("ID", cookie.getName());
        assertEquals("Vincent", cookie.getValue());
    }

    /**
     * Test the output stream returned by the <code>doGet()</code> method.
     */
    public void testDoGet()
    {
        SimpleServlet servlet = new SimpleServlet();
        servlet.doGet(request, response);
    }

    /**
     * Test the output stream returned by the <code>doGet()</code> method.
     */
    public void endDoGet(HttpURLConnection theConnection)
    {
        assertEquals("<html><head/><body><h1>Your name is Vincent</h1></body></html>",
            AssertUtils.getResponseAsString(theConnection));
    }
}

Notice that in the endRegisterUser() and endDoGet() test methods we use methods from a helper class provided by J2EEUnit to help retrieve cookies sent back from the servlet and to help assert the returned servlet output stream.

For unanswered questions, see the section on using J2EEUnit and the FAQ.