1 說明
我們給出三個頁面：index.jsp、user.jsp、admin.jsp。
index.jsp：誰都可以訪問，沒有限制；
user.jsp：只有登錄用戶才能訪問；
admin.jsp：只有管理員才能訪問。
2 分析
設計User類：username、password、grade，其中grade表示用戶等級，1表示普通用戶，2表示管理員用戶。
當用戶登錄成功后，把user保存到session中。
創建LoginFilter，它有兩種過濾方式：
如果訪問的是user.jsp，查看session中是否存在user；
如果訪問的是admin.jsp，查看session中是否存在user，并且user的grade等于2。
3 代碼
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <servlet> <servlet-name>LoginServlet</servlet-name> <servlet-class>com.cug.web.servlet.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/LoginServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <filter> <filter-name>UserFilter</filter-name> <filter-class>com.cug.filter.UserFilter</filter-class> </filter> <filter-mapping> <filter-name>UserFilter</filter-name> <url-pattern>/user/*</url-pattern> </filter-mapping> <filter> <filter-name>AdminFilter</filter-name> <filter-class>com.cug.filter.AdminFilter</filter-class> </filter> <filter-mapping> <filter-name>AdminFilter</filter-name> <url-pattern>/admin/*</url-pattern> </filter-mapping> </web-app>
LoginServlet.java
package com.cug.web.servlet;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.cug.domain.User;import com.cug.web.service.UserService;public class LoginServlet extends HttpServlet{ @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setCharacterEncoding("utf-8"); resp.setContentType("text/html;charset=utf-8"); String username = req.getParameter("username"); String password = req.getParameter("password"); User user = UserService.login(username, password); if(user == null){ req.setAttribute("msg", "用戶名或者密碼錯誤"); req.getRequestDispatcher("/login.jsp").forward(req, resp); } else{ req.getSession().setAttribute("user", user); req.getRequestDispatcher("index.jsp").forward(req,resp); } }}UserService
package com.cug.web.service;import java.util.HashMap;import java.util.Map;import com.cug.domain.User;public class UserService { private static Map<String, User> users = new HashMap<String, User>(); static{ users.put("zhu", new User("zhu", "123", 2)); users.put("xiao", new User("xiao", "123", 1)); } public static User login(String username, String password){ User user = users.get(username); if(user == null) return null; if(!user.getPassword().equals(password)) return null; return user; }}AdminFilter
package com.cug.filter;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import com.cug.domain.User;public class AdminFilter implements Filter{ @Override public void destroy() { } @Override public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException { req.setCharacterEncoding("utf-8"); resp.setContentType("text/html;charset=utf-8"); HttpServletRequest request = (HttpServletRequest)req; User user = (User)request.getSession().getAttribute("user"); if(user == null){ resp.getWriter().print("用戶還沒有登陸"); request.getRequestDispatcher("/login.jsp").forward(req, resp); } if(user.getGrade() < 2){ resp.getWriter().print("您的等級不夠"); return; } chain.doFilter(req, resp); } @Override public void init(FilterConfig arg0) throws ServletException { }}UserFilter
package com.cug.filter;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import com.cug.domain.User;public class UserFilter implements Filter{ @Override public void destroy() { } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { request.setCharacterEncoding("utf-8"); response.setContentType("text/html;charset=utf-8"); HttpServletRequest httpReq = (HttpServletRequest)request; User user = (User)httpReq.getSession().getAttribute("user"); if(user == null){ request.getRequestDispatcher("/login.jsp").forward(request, response); } chain.doFilter(request, response); } @Override public void init(FilterConfig filterConfig) throws ServletException { }}User
package com.cug.domain;public class User { private String username; private String password; private int grade; public User() { super(); } public User(String username, String password, int grade) { super(); this.username = username; this.password = password; this.grade = grade; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public int getGrade() { return grade; } public void setGrade(int grade) { this.grade = grade; } @Override public String toString() { return "User [username=" + username + ", password=" + password + ", grade=" + grade + "]"; }}html
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > <title>My JSP 'admin.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > --> </head> <body> <h1>admin.jsp</h1> <h3>${user.username }</h3> <a href="<c:url value='/index.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >首頁</a><br/> <a href="<c:url value='/user/user.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >用戶頁</a><br/> <a href="<c:url value='/admin/admin.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >系統管理員</a><br/> </body> </html>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > <title>My JSP 'user.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > --> </head> <body> <h1>user.jsp</h1> <h3>${user.username }</h3> <a href="<c:url value='/index.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >首頁</a><br> <a href="<c:url value='/user/user.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >用戶登陸界面</a><br> <a href="<c:url value='/admin/admin.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >管理員登陸界面</a><br> </body> </html> 用戶登錄
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > <title>My JSP 'login.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > --> </head> <body> ${msg } <form action="<c:url value='/LoginServlet'/>" method="post"> 用戶名：<input type="text" name="username"/><br/> 密碼：<input type="password" name="password"/><br/> <input type="submit" value="登陸"/> </form> </body> </html>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > --> </head> <body> <h1>index.jsp</h1> <h3>${user.username }</h3> <a href="<c:url value='/index.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >首頁</a><br> <a href="<c:url value='/user/user.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >用戶登陸界面</a><br> <a href="<c:url value='/admin/admin.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >管理員登陸界面</a><br> </body> </html>
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