jsp

package com.hbsi.csdn.SessionTest;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class ShoppingLogin extends HttpServlet {

 /**
  * Constructor of the object.
  */
 public ShoppingLogin() {
  super();
 }

 /**
  * Destruction of the servlet. <br>
  */
 public void destroy() {
  super.destroy(); // Just puts "destroy" string in log
  // Put your code here
 }

 /**
  * The doGet method of the servlet. <br>
  *
  * This method is called when a form has its tag value method equals to get.
  *
  * @param request
  *            the request send by the client to the server
  * @param response
  *            the response send by the server to the client
  * @throws ServletException
  *             if an error occurred
  * @throws IOException
  *             if an error occurred
  */
 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  this.doPost(request, response);
 }

 /**
  * The doPost method of the servlet. <br>
  *
  * This method is called when a form has its tag value method equals to
  * post.
  *
  * @param request
  *            the request send by the client to the server
  * @param response
  *            the response send by the server to the client
  * @throws ServletException
  *             if an error occurred
  * @throws IOException
  *             if an error occurred
  */
 public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  response.setContentType("text/html;charset=GB2312");
  PrintWriter out = response.getWriter();

  String username = request.getParameter("username");

  HttpSession session = request.getSession();
  
  String sessionName = (String) session.getAttribute("name");
  if (sessionName != null) {  //判斷session中是否爲空，不爲空則直接跳轉到處理購物的servlet中
   RequestDispatcher rd = request
     .getRequestDispatcher("CoursesServlet");
   rd.forward(request, response);
  }

  if (username == null || username.trim().equals("")) {// 判斷用戶名是否爲空，不爲空則轉發到處理購物的servlet中，否則跳轉到原來登錄的頁面
   out.println("請輸入用戶名!");
   RequestDispatcher rd = request
     .getRequestDispatcher("ShoppingLogin.html");
   rd.include(request, response);
  } else {
   session.setAttribute("name", username);
   RequestDispatcher rd = request
     .getRequestDispatcher("CoursesServlet");
   rd.forward(request, response);
  }
 }

 /**
  * Initialization of the servlet. <br>
  *
  * @throws ServletException
  *             if an error occurs
  */
 public void init() throws ServletException {
  // Put your code here
 }

}