loginservlet.java

EJB实践的服务器是用SUN的服务器

package examples;

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

/**
 * This is the very first servlet the client deals with.
 * It's a Login authentication servlet. It asks the user
 * for his name and password, and pass it to the UserManager
 * stateless session bean for verificatiion. 
 * If the user authenticates properly, reference to a new
 * Cart is saved in his HttpSession object, and the user can
 * begin to add items to his cart and shop around.
 */
public class LoginServlet 
    extends HttpServlet 
{

    /*
     * UserManager home object for authenticating user
     */
    private UserManagerHome userManagerHome;

    /*
     * Cart home object for creating a new cart when
     * the user logs in.
     */
    private CartHome cartHome;

    /**
     * The servlet engine calls this method once to
     * initialize a servlet instance.
     *
     * In the body of this method, we acquire all the
     * EJB home objects we'll need later.
     */
    public void init(ServletConfig config) 
        throws ServletException 
    {
        super.init(config);

        try 
        {
            /*
             * Get the initial JNDI context using the above
             * startup params.
             */
            Context ctx = new InitialContext();

            /*
             * Look up the UserManager and Cart Home Objects
             * we need via JNDI
             */
            userManagerHome = 
                (UserManagerHome)ctx.lookup("ejb/UserManagerHome");

            cartHome = 
                (CartHome)ctx.lookup("ejb/CartHome");
        }
        catch (Exception e) 
        {
            log(e);
            throw new ServletException(e.toString());
        }
    }

    /**
     * The servlet engine calls this method when the user's
     * desktop browser sends an HTTP request.
     */
    public void service(HttpServletRequest request,
                        HttpServletResponse response)
        throws ServletException, IOException 
    {
        /*
         * Set up the user's HttpSession
         */
        HttpSession session = request.getSession(true);

        /*
         * Retrieve the login name / password from the
         * URL string.
         */
        String loginName = request.getParameter("Login");
        String password = request.getParameter("Password");
        boolean isLogin = false;
  
        /*
         * If user has not tried to log in yet, present
         * him with the login screen.
         */
        if ((loginName == null) || (password == null)) 
        {
            writeForm(request, response, false);
            return;
        }
        else 
        {
            /*
             * Otherwise, the user has been to this screen
             * already, and has entered some information.
             * Verify that information.
             */
            try 
            {
                /*
                 * Uses the UserManager Stateless Session bean to
                 * autenticate the user credentials.
                 */
                UserManager userManager = userManagerHome.create();
                isLogin = userManager.validateUser(loginName,password);
            }
            catch (Exception e) {
                writeForm(request, response, true);
                e.printStackTrace();
                return;
            }
            /*
             * If the passwords match, make a new Cart Session
             * Bean, and add it to the user's HttpSession
             * object.  When the user navigates to other
             * servlets, the other servlets can access the
             * HttpSession to get the user's Cart.
             */
            if (isLogin) 
            {
                try 
                {
                    Cart cart = cartHome.create(loginName);
                    session.setAttribute("cart", cart);
     
                    /*
                     * Call the main page
                     */
                    RequestDispatcher disp =
                        this.getServletContext().getRequestDispatcher("/wsf.jsp");
                    disp.forward(request, response);
     
                    return;
                }
                catch (Exception e) {
                    log(e);
                    throw new ServletException(e.toString());
                }
            }
        }
  
        /*
         * If there was no match, the user is
         * not authenticated.  Present another
         * login screen to him, with an error
         * message indicating that he is not
         * authenticated.
         */
        writeForm(request, response, true);
    }

    /**
     * Writes the Login Screen (private use only)
     *
     * @param showError true means show an error b/c client
     *        was not authenticated last time.
     */
    private void writeForm(HttpServletRequest request,
                           HttpServletResponse response,
                           boolean showError)
        throws ServletException, IOException {

        /*
         * Set a variable indicating whether or not we failed to
         * log-in.  The JSP will read this variable.
         */
        request.setAttribute("loginFailed", new Boolean(showError));
    
        /*
         * Forward the request to the login JSP
         */
        RequestDispatcher disp =
            this.getServletContext().getRequestDispatcher("/login.jsp");
        disp.forward(request, response);
    }

    private void log(Exception e) {
        e.printStackTrace();
    }

    public String getServletInfo() {
        return "The Login servlet verifies a user.";
    }
}