Filter的基本用法一
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Filter的基本用法一
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一、當登錄了Admin用戶后，可以訪問Admin的文件夾，如下圖所示：
當不是admin用戶，或者是普通用戶登錄時
具體代碼如下：
首先是webroot下的兩個文件
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% 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%>"><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">--><link rel="stylesheet" href="bootstrap/css/bootstrap.min.css"> <script src="jquery/jquery.js"></script><script src="bootstrap/js/bootstrap.min.js"></script> <script src="jquery/jquery.json-2.3.js"></script><script>function trace(msg){try{console.log(msg);}catch(err){}}//頁面加載后的初始化工作$(document).ready(function(){});</script></head><body><div class="container"><h1>----------首頁----------</h1><%String user=(String)request.getSession().getAttribute("user");if(user!=null){out.print(user+"你好");}else{out.print("<a href='login.jsp'>請登錄</a>");}%></div></body> </html>login.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% 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%>"><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">--></head><body><form method="post" action="servlet/LoginServlet">用戶名：<input type="text" name="user"><br><br>密碼：<input type="password" name="password"><br><br><input type="submit" value="登錄"> </form></body> </html>/admin/? ?目錄下有2個文件，一個是圖片，一個是admin.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% 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%>"><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">--></head><body><h1>----------admin后臺管理界面----------</h1></body> </html>下面是一個Servlet
package my;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 LoginServlet extends HttpServlet {/*** Constructor of the object.*/public LoginServlet() {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 {response.setContentType("text/html");PrintWriter out = response.getWriter();out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");out.println("<HTML>");out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");out.println(" <BODY>");out.print(" This is ");out.print(this.getClass());out.println(", using the GET method");out.println(" </BODY>");out.println("</HTML>");out.flush();out.close();}/*** 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 {String user=request.getParameter("user");String password=request.getParameter("password");if(password.equals("123456")){HttpSession hs=request.getSession();hs.setAttribute("user", user);//mywebString contextPath=request.getContextPath();if(user.equals("admin")){response.sendRedirect(contextPath+"/admin/index.jsp");}else{response.sendRedirect(contextPath+"/index.jsp");}}else{response.sendError(400,"用戶名/密碼有誤!");}}/*** Initialization of the servlet. <br>** @throws ServletException if an error occurs*/public void init() throws ServletException {// Put your code here}}隨后是SampleFilter.java
package my;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 javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession;public class SampleFilter implements Filter{@Overridepublic void destroy() {// TODO Auto-generated method stub}@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {HttpServletRequest httpReq=(HttpServletRequest)request;HttpServletResponse httpResp=(HttpServletResponse)response;HttpSession hs=(HttpSession)httpReq.getSession();String clientIp=httpReq.getRemoteAddr();//check userString user=(String)hs.getAttribute("user");if(!"admin".equals(user)){httpResp.sendError(400,"你不是admin用戶，無權訪問！");return;}//繼續chain.doFilter(request, response);}@Overridepublic void init(FilterConfig arg0) throws ServletException {// TODO Auto-generated method stub} }此時要注意WEB-INF文件夾里面的web.xml要做如下配置：
<?xml version="1.0" encoding="UTF-8"?> <web-app version="3.0" 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_3_0.xsd"><display-name></display-name><filter><filter-name>SampleFilter</filter-name><filter-class>my.SampleFilter</filter-class></filter><filter-mapping><filter-name>SampleFilter</filter-name><url-pattern>/admin/*</url-pattern></filter-mapping><servlet><description>This is the description of my J2EE component</description><display-name>This is the display name of my J2EE component</display-name><servlet-name>LoginServlet</servlet-name><servlet-class>my.LoginServlet</servlet-class></servlet><servlet-mapping><servlet-name>LoginServlet</servlet-name><url-pattern>/servlet/LoginServlet</url-pattern></servlet-mapping> <welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list> </web-app>總結
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