过滤器[登录+编码]filter在程序中的使用

虽然很久没有写WEB程序了，但依然怀念那些写WEB和日子。看了下以前的毕业设计，从中提取说一些小例子。写在这里。

这里讲解的是其中filter中使用。主要用于两个方面。一个是编码的设置和登录的拦截验证。

众所周知，java的乱码有时是个很头疼的问题。你不是不在每个页面定义一个编码，还得在每个servlet或action中定义编码。

通常见到这样的几行代码：

request.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset=UTF-8");

这对于一个庞大的系统来说，显得有点太多余。

我们要做一就是简化开发，提高效率。

<!--配置过滤器--><filter><filter-name>LoginFilter</filter-name><filter-class>com.tudou.projectmanage.filters.LoginFilter</filter-class></filter><filter-mapping><filter-name>LoginFilter</filter-name><!--过滤处理访问/view/admin下所有资源的请求--><url-pattern>/view/admin/*</url-pattern></filter-mapping><filter><filter-name>EncodingFilter</filter-name><filter-class>com.tudou.projectmanage.filters.EncodingFilter</filter-class><init-param><param-name>encoding</param-name><param-value>UTF-8</param-value></init-param></filter><filter-mapping><filter-name>EncodingFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping>

上面定义两个过滤器，一个用于拦截登录[admin文件夹下为需要过滤的主界面，此处为管理后台页面，注：login.jsp等页面不在此列，如果你连login页面都过滤了，你还指望谁来登录你的网站呢。]

<!--过滤处理访问/view/admin下所有资源的请求--><url-pattern>/view/admin/*</url-pattern>

一个用于处理编码

<url-pattern>/*</url-pattern>

。

写一个过滤器，继承Filter即可。实现其中的doFilter方法。在其init方法初始化编码即可。这样一个编码的拦截器就实现了。

package com.tudou.projectmanage.filters;/** * 处理乱码 * @author tudou * @date  2011-06-02 */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.HttpServlet;@SuppressWarnings("serial")public class EncodingFilter extends HttpServlet implements Filter {FilterConfig config;private String encoding = null;public EncodingFilter() {}public void doFilter(ServletRequest request, ServletResponse response,FilterChain filterChain) throws IOException, ServletException {if (encoding != null) {request.setCharacterEncoding(encoding);response.setContentType("text/html;charset="+encoding);}filterChain.doFilter(request, response);}public void init(FilterConfig config) throws ServletException {this.config = config;encoding = config.getInitParameter("encoding");}@Overridepublic void destroy() {config = null;}}

同理登录拦截是一样的道理，只是处理方式略有不同。

package com.tudou.projectmanage.filters;/** * 此类用于拦截登录 * 配置于web.xml节点的filter * @author tudou * @date  2011-06-02 */import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletContext;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;import com.tudou.projectmanage.persist.Users;@SuppressWarnings("serial")public class LoginFilter extends HttpServlet implements Filter {/** *  */FilterConfig config;public LoginFilter() {}/** * 核心过滤器 防止前台非法访问！！！ 查询条件为memberTypeName是管理员并且未被禁用 3重验证 */public void doFilter(ServletRequest request, ServletResponse response,FilterChain filterChain) throws IOException, ServletException {HttpServletRequest req = (HttpServletRequest) request;HttpServletResponse res = (HttpServletResponse) response;HttpSession session = req.getSession(true);Users user = (Users) session.getAttribute("user");if (user != null) {filterChain.doFilter(req, res);//用户验证通过return;} else {req.setAttribute("title", "您还没有登录");req.setAttribute("messages", "请先登录！");// 进入后台登录页面req.setAttribute("page", "login.jsp");ServletContext ctx = config.getServletContext();ctx.getRequestDispatcher("/view/exceptions/error.jsp").forward(req,res);}}public void init(FilterConfig config) throws ServletException {this.config = config;}@Overridepublic void destroy() {config = null;}}

如此一个登录拦截就完成了。

注：

此登录只过滤了../amdin文件夹下的资源。如果有人通过.do/.action/servlet的方式直接进行后台操作是拦截不到的。

此时，必须借助于拦截器进行URL拦截才能达到真正的完全拦截。一般用于权限控制。防止非法后台操作。

附上

error.jsp:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri="/struts-tags" prefix="s"%><%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>提示</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="css/common.css"><style type="text/css">body {text-align: center;}#content {font-size: 15px;}</style><script language="javascript">var index = 5;var t;function timeStart() {document.getElementById("second").innerHTML = index;if (index <= 1) {var page = document.getElementById("page").value;if (page) {if (page == "login.jsp") {window.parent.location.href = "/projectManageSystem/login";} else if (page == "index.jsp") {window.parent.location.href = "/projectManageSystem/index.jsp";} else {if (page == "left.jsp") {parent.frames.leftFrame.location.reload();window.location.href = "showmenu!showMenus.action?todo=0";return;}window.location.href = page;}} else {history.go(-1);}clearTimeout(t);return;}index--;t = setTimeout("timeStart()", 1000);}function goTo() {var page = document.getElementById("page").value;if (page) {if (page == "login.jsp") {window.parent.location.href = "/projectManageSystem/login";} else if (page == "index.jsp") {window.parent.location.href = "/projectManageSystem/index.jsp";} else {if (page == "left.jsp") {parent.frames.leftFrame.location.reload();window.location.href = "showmenu!showMenus.action?todo=0";return;}window.location.href = page;}} else {history.go(-1);}}</script></head><body onload="timeStart()"><script>history.go(1);</script><DIV><TABLE height="97%" cellSpacing=0 cellPadding=0 width="99%" border=0><TBODY><TRstyle="BACKGROUND-IMAGE: url(images/common/bg_header.gif); BACKGROUND-REPEAT: repeat-x"height=47><TD width=10><SPANstyle="FLOAT: left; BACKGROUND-IMAGE: url(images/common/main_hl.gif); WIDTH: 15px; BACKGROUND-REPEAT: no-repeat; HEIGHT: 47px"></SPAN></TD><TD><SPANstyle="FLOAT: left; BACKGROUND-IMAGE: url(images/common/main_hl2.gif); WIDTH: 15px; BACKGROUND-REPEAT: no-repeat; HEIGHT: 47px"></SPAN><SPANstyle="PADDING-RIGHT: 10px; PADDING-LEFT: 10px; FLOAT: left; BACKGROUND-IMAGE: url(images/common/main_hb.gif); PADDING-BOTTOM: 10px; COLOR: white; PADDING-TOP: 10px; BACKGROUND-REPEAT: repeat-x; HEIGHT: 47px; TEXT-ALIGN: center; 0 px: ">提示界面 </SPAN><SPANstyle="FLOAT: left; BACKGROUND-IMAGE: url(images/common/main_hr.gif); WIDTH: 60px; BACKGROUND-REPEAT: no-repeat; HEIGHT: 47px"></SPAN></TD><TDstyle="BACKGROUND-POSITION: 50% bottom; BACKGROUND-IMAGE: url(images/common/main_rc.gif)"width=10></TD></TR><TR><TD style="BACKGROUND-IMAGE: url(images/common/main_ls.gif)"> </TD><TD style="COLOR: #566984; BACKGROUND-COLOR: white;"vAlign="middle" align="center"><div id="content"><div style="text-align: center; height: 12px;">${title}</div><hr color="lightblue" size="1" /><div align="center" style="height: 50px;"><br />${messages}<span style="font-size: 15px; color: red;"><s:actionerror /></span><input type="hidden" id="page" value="${page}" /><br /><br /><span style="font-size: 12px; color: gray;"> <labelid="second" style="color: red;"></label> 秒后自动跳转,如果浏览器不支持跳转,请<a href="javascript:void(0);" onclick="goTo();">点击这里</a> </span></div></div></TD><TD style="BACKGROUND-IMAGE: url(images/common/main_rs.gif)"></TD></TR><TRstyle="BACKGROUND-IMAGE: url(images/common/main_fs.gif); BACKGROUND-REPEAT: repeat-x"height=10><TD style="BACKGROUND-IMAGE: url(images/common/main_lf.gif)"></TD><TD style="BACKGROUND-IMAGE: url(images/common/main_fs.gif)"></TD><TD style="BACKGROUND-IMAGE: url(images/common/main_rf.gif)"></TD></TR></TBODY></TABLE></DIV></body></html>