CODEWITHSUNDEEP
javajspservlets
Tom
Tom

Reputation: 2349

JSP - javabean returns null, but why?

When an user presses the login button on a JSP, the request is submitted to my servlet which gets the entered username and password from the login form by getParameter().

The username and password are stored in a javabean. If I put a println() statement which shows the values of bean.getUsername() and bean.getPassword(), then it prints the username and password in the log.

But the following code snippet on my master page

<jsp:useBean id="bean" class="package.Bean" scope="session" />
<jsp:getProperty name="bean" property="username" />

shows null instead of the username. What am I doing wrong?

protected void doPost(HttpServletRequest request, HttpServletResponse response)
                        throws ServletException, IOException
{
    String username = request.getParameter("username");
    String password = request.getParameter("password");

    // Store username and password in bean from login.jsp
    Bean bean = new bean();
    bean.setUsername(username);
    bean.setPassword(password);

    // check login details with database

       if (login success)
    {   
        HttpSession session = request.getSession();
        session.setAttribute("username", username);

        // redirect user to welcome page
    }
    else
        // login failed
}

Upvotes: 1

Views: 4032

Answers (1)

BalusC
BalusC

Reputation: 1109542

Likely you haven't let the servlet store the bean in the session scope. But since you're using servlets anyway, forget the <jsp:useBean> thing. It's technically worthless. It also tight-couples the model with the view.

Just let the servlet put the bean in session scope:

User user = userDAO.find(username, password);
if (user != null) {
    request.getSession().setAttribute("user", user); // Store logged-in user in session.
    response.sendRedirect("home"); // Redirect to login home page or whatever.
} else {
    request.setAttribute("message", "Unknown login, please try again"); // Store error message for redisplay in login page.
    request.getRequestDispatcher("/WEB-INF/login.jsp").forward(request, response); // Forward to login page.
}

Then in the user home page, just use EL (Expression Language) to access the User bean.

<p>Welcome, <c:out value="${user.username}" /></p>

The ${foo} basically searches for an attribute which is stored with the name foo in page, request, session and application scopes and returns the first non-null value. In this case, the ${user} will refer to your User bean which you've stored in the session scope. The ${user.username} will basically display the return value of user.getUsername().

The <c:out> is by the way not necessary, but it prevents your page from potential XSS attacks.

See also:

Unrelated to the concrete problem, package is a keyword and thus an illegal package name. Please take care when posting oversimplified code examples ;) Rather use com.example or something if you'd like to obfuscate package names.

Update: as per your update, you're setting the username in the session scope, not the bean itself. Even though you would be able to display it by ${username}, in order to be able to use ${bean.username}, you need to fix it accordingly as described in above answer.

Upvotes: 2

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