javaweb设计中filter粗粒度权限控制代码示例

1 说明

我们给出三个页面：index.jsp、user.jsp、admin.jsp。

index.jsp：谁都可以访问，没有限制；

user.jsp：只有登录用户才能访问；

admin.jsp：只有管理员才能访问。

2 分析

设计User类：username、password、grade，其中grade表示用户等级，1表示普通用户，2表示管理员用户。

当用户登录成功后，把user保存到session中。

创建LoginFilter，它有两种过滤方式：

如果访问的是user.jsp，查看session中是否存在user；
如果访问的是admin.jsp，查看session中是否存在user，并且user的grade等于2。

3 代码

<?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", "用户名或者密码错误");
			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("用户还没有登陆");
			request.getRequestDispatcher("/login.jsp").forward(req, resp);
		}
		if(user.getGrade() < 2){
			resp.getWriter().print("您的等级不够");
			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" >首页</a><br/>
 <a href="<c:url value='/user/user.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >用户页</a><br/>
 <a href="<c:url value='/admin/admin.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >系统管理员</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" >首页</a><br>
 <a href="<c:url value='/user/user.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >用户登陆界面</a><br>
 <a href="<c:url value='/admin/admin.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >管理员登陆界面</a><br>
 </body>
</html> 

用户登录

<%@ 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">
  用户名：<input type="text" name="username"/><br/>
  密码：<input type="password" name="password"/><br/>
  <input type="submit" value="登陆"/>
 </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" >首页</a><br>
 <a href="<c:url value='/user/user.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >用户登陆界面</a><br>
 <a href="<c:url value='/admin/admin.jsp'/>" rel="external nofollow" rel="external nofollow" rel="external nofollow" >管理员登陆界面</a><br>
 </body>
</html> 

总结

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