现在要进行一个实验：实验二 Servlet进阶和
JSP基础
一、实验目的
（1）掌握Servlet处理session以及Cookie的方法。
（2）掌握
JSP的编写方法。
（3）掌握
JSP中变量、表达式的使用。
二、 实验环境和要求
（1）使用Eclipse、Tomcat以及
浏览器等作为实验环境。
（2）实验前应做好设计规划，充分准备，对各个问题预先编制程序。
（3）在实验中遇到困难时运用多种手段解决问题。
三、 实验内容
（1） 使用表单提交的方式交给Servlet处理，完成用户登录以及退出操作，并利用会话和Cookie实现自动登录功能。我创建了一个login
.jsp，代码为：<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String username = "";
String password = "";
Cookie[] cookies = request
.getCookies();
if(cookies!= null){
String userinfo = null;
for(int i=0;i<cookies
.length;i++){
if(cookies[i]
.getName( )
.equals("userinfo")){
userinfo= cookies[i]
.getValue();
break;
}
}
if(userinfo!=null){
String[ ] information = userinfo
. split("\\|" );
username=information[0];
password= information[1];
}
}
%>
<form action = "LoginServlet" method="post">
用户名：<input type = "text" name = "username" value = <%= username %>>
<br>
密 码:
<input type = "password" name = "password" value = <%= password %>><br>
<input type = "submit" value = "登录"><input type = "reset" value = "重置">
</form>
</body>
</html>，又创建了一个LoginServlet，代码为：package com
.test
.servlet;
import java
.io
.IOException;
import javax
.servlet
.ServletException;
import javax
.servlet
.annotation
.WebServlet;
import javax
.servlet
.http
.Cookie;
import javax
.servlet
.http
.HttpServlet;
import javax
.servlet
.http
.HttpServletRequest;
import javax
.servlet
.http
.HttpServlet
Response;
import javax
.servlet
.http
.HttpSession;
/**
* Servlet implementation class LoginServlet
*/
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServlet
Response response)
*/
protected void doGet(HttpServletRequest request, HttpServlet
Response response) throws ServletException, IOException {
// TODO Auto-generated method stub
request
.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
response.setHeader("Content-type","text/plain;charset = UTF -8" );
String username = request
.getParameter("username");
String password= request
.getParameter("password" );
if(username!=null&&password!= null) {
if(username
.equals(password)) {
HttpSession session = request
.getSession();
session
.setAttribute("username", username);
Cookie userinfocookie = new Cookie("userinfo" ,username + "|"+ password);
userinfocookie
.setMaxAge(60*5);
response.addCookie(userinfocookie);
response.sendRedirect("welcome
. jsp" );
}else {
//跳转到欢迎页面
response.getWriter()
.append("用户名密码错误,请重新登录5 秒后回到登录页面……");
response.setHeader("Refresh","5;URL= login
.jsp");
}
}else {
response.getWriter()
.append("禁止直接访问,5秒后回到登录页面……");
response.setHeader("Refresh","5;URL = login
.jsp");
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServlet
Response response)
*/
protected void doPost(HttpServletRequest request, HttpServlet
Response response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request,
response);
}
}
，接着创建了一个welcome
.jsp，代码为：<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
response.setHeader("Pragma" ,"No - Cache" );
response.setHeader( "Cache - Control" , "No - Cache" );
response.setDateHeader("Expires",0);
if(session!= null){
String username =(String)session
.getAttribute("username");
if(username!=null)
{out
.print("欢迎您,"+ username + "<a href ='LogoutServlet'>安全退出</a>");
}
else {
out
.print("你还没有登录,5秒后跳转到登录页面……");
response.setHeader("Refresh","5;URL=login
.jsp");
}
}else{
out
.print("禁止直接访问,5秒后跳转到登录页面……");
response.setHeader("Refresh","5;URL=login
.jsp");
}
%>
</body>
</html>，最后创建了一个LogoutServlet，代码为：package com
.test
.servlet;
import java
.io
.IOException;
import javax
.servlet
.ServletException;
import javax
.servlet
.annotation
.WebServlet;
import javax
.servlet
.http
.Cookie;
import javax
.servlet
.http
.HttpServlet;
import javax
.servlet
.http
.HttpServletRequest;
import javax
.servlet
.http
.HttpServlet
Response;
import javax
.servlet
.http
.HttpSession;
/**
* Servlet implementation class LogoutServlet
*/
@WebServlet("/LogoutServlet")
public class LogoutServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LogoutServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServlet
Response response)
*/
protected void doGet(HttpServletRequest request, HttpServlet
Response response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setCharacterEncoding("UTF-8");
response.setHeader("Content- type" ,"text/plain;charset = UTF - 8" );//判断当前请求是否存在对象
HttpSession session =request
.getSession(false);
if(session!= null) {
session
.invalidate();
Cookie usernameinfo = new Cookie("userinfo" , "" );
usernameinfo
.setMaxAge(0);
response.addCookie(usernameinfo);
response.getWriter()
.append("注销成功,5秒后跳转到登录页面……");
response. setHeader("Refresh", "5;URL, = login
. jsp" );
}else{
response.getWriter()
.append("你还未登录，无须注销5秒后跳转到登录页面……");
response. setHeader(" Refresh", "5 ;URL = login
. jsp" );
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServlet
Response response)
*/
protected void doPost(HttpServletRequest request, HttpServlet
Response response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request,
response);
}
}
，请问能完成这个实验的要求吗，如果不能请在我的代码上改动
本文探讨了通过使用response.sendRedirect(response.encodeURL(url))来保证不同页面间Session对象的一致性，这种方法尤其适用于当浏览器不支持或禁用了COOKIE的情况，有效地避免了session跟踪失败的问题。
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