servlet中session简介和使用例子

<meta name="keywords" content="keyword1,keyword2,keyword3" />
<meta name="description" content="this is my page" />
<meta name="content-type" content="text/html; charset=UTF-8" />

 <!--    <link rel="stylesheet" type="text/css" href="./styles.css">--></pre>
<form action="servlet/saveinfo" method="post">
 用户名:
 <input type="text" name="username" /> <input type="submit" />

 密码:
 <input type="password" name="userpasswd" />

 </form>
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package chap03;

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

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 saveinfo extends HttpServlet {

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

/
  Destruction of the servlet.

 /
 public void destroy() {
 super.destroy(); // Just puts "destroy" string in log
 // Put your code here
 }

/
  The doGet method of the servlet.

 
  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 ourred
  @throws IOException if an error ourred
 /
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

 //如果用户输入过了用户名 则将其放在session中
 if(request.getParameter("username")!=null);
 {
 HttpSession session = request.getSession();
 session.setAttribute("username",request.getParameter("username"));
 }
 response.setContentType("text/html;charset=GBK");
 PrintWriter out = response.getWriter();
 out.println("session已经创建");
 out.println("
");
 out.println("跳转到其他<a>页面</a>");

 }

/
  The doPost method of the servlet.

 
  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 ourred
  @throws IOException if an error ourred
 /
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

 doGet(request,response);
 }

/
  Initialization of the servlet.

 
  @throws ServletException if an error ours
 /
 public void init() throws ServletException {
 // Put your code here
 }

}</pre>
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package chap03;

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

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 getsession extends HttpServlet {

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

/
  Destruction of the servlet.

 /
 public void destroy() {
 super.destroy(); // Just puts "destroy" string in log
 // Put your code here
 }

/
  The doGet method of the servlet.

 
  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 ourred
  @throws IOException if an error ourred
 /
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

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

 String username = "";
 //此处不是创建session 而是去取已经创建的session
 HttpSession session = request.getSession();
 //如果已经取到，说明已经登录
 if(session!=null)
 {
 username = (String)session.getAttribute("username");
 out.println("获得创建的Session");
 out.println("
");
 out.println("登录名:"+username);
 }
 else
 {
 response.sendRedirect("../sessionlogin.html");
 }
 }

/
  The doPost method of the servlet.

 
  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 ourred
  @throws IOException if an error ourred
 /
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 doGet(request,response);
 }

/
  Initialization of the servlet.

 
  @throws ServletException if an error ours
 /
 public void init() throws ServletException {
 // Put your code here
 }

}</pre>
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