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");
	}

	@Override
	public 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;
	}

	@Override
	public 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>
					<TR
						style="BACKGROUND-IMAGE: url(images/common/bg_header.gif); BACKGROUND-REPEAT: repeat-x"
						height=47>
						<TD width=10>
							<SPAN
								style="FLOAT: left; BACKGROUND-IMAGE: url(images/common/main_hl.gif); WIDTH: 15px; BACKGROUND-REPEAT: no-repeat; HEIGHT: 47px"></SPAN>
						</TD>
						<TD>
							<SPAN
								style="FLOAT: left; BACKGROUND-IMAGE: url(images/common/main_hl2.gif); WIDTH: 15px; BACKGROUND-REPEAT: no-repeat; HEIGHT: 47px"></SPAN><SPAN
								style="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>
							<SPAN
								style="FLOAT: left; BACKGROUND-IMAGE: url(images/common/main_hr.gif); WIDTH: 60px; BACKGROUND-REPEAT: no-repeat; HEIGHT: 47px"></SPAN>
						</TD>
						<TD
							style="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;"> <label
											id="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>
					<TR
						style="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>