404 error code .. help plz

Question

Hi all,
how can I catch the 404 errors in my jsp page to throw these excptions to My errorPage ??
I write in My home Page (index.jsp) to catch this error :
try {
// My code
} catch(FileNotFoundException ex) {
throw new FileNotFoundException("page not found");
and I write in the web.xml Page :
<web-app>
<display-name>Orange Whip Studios</display-name>
<description>JRun Web Application Construction Kit Demo</description>
<context-param>
<param-name>CompanyName</param-name>
<param-value>Orange Whip Studios</param-value>
</context-param>
<context-param>
<param-name>Datasource</param-name>
<param-value>ows</param-value>
</context-param>
<error-page>
<error-code>404</error-code>
<location>/errorPage.jsp</location>
</error-page>
<error-page>
<error-code>500</error-code>
<location>/errorPage.jsp</location>
</error-page>
<error-page>
<exception>java.sql.Exception</exception>
<location>/errorPage.jsp</location>
</error-page>
</web-app>
the 500 error code and the java.sql.Exception work finally .. but the 404 error code didn't ??? can anyone tell me why????

Answer 1

You aren't forwarding the request to a JSP at any way. Use RequestDispatcher#forward() for that.
I also recommend to separate your logic. Use DAO class for the database logic. Use servlet class for the business logic and use JSP for the view logic. E.g.
// Process request parameters.
String username = request.getParameter("username");
String password = request.getParameter("password");
// Get User from DAO.
User user = yourUserDAO.loadUser(username, password);
// Check User.
if (user != null) {
    // User exist.
    request.getSession().setAttribute("user", user);
    request.setAttribute("isLoggedIn", Boolean.TRUE);
} else {
    // User doesn't exist.
    request.setAttribute("isLoggedIn", Boolean.FALSE);
// Forward request back to login JSP file.
request.getRequestDispatcher("login.jsp").forward(request, response);login.jsp:<p>Login ${isLoggedIn ? 'succesful' : 'failed'}</p>or use JSTL c:if / c:choose.
Besides, why don't you trust the database? You're querying the database for a single row matching the username and password. If it returns a row, then you're comparing the username and password once again in Java. Why?