过滤器是什么玩意？
所谓过滤器，其实就是一个服务端组件，用来截取用户端的请求与响应信息。
过滤器的应用场景：
1.对用户请求进行统一认证，保证不会出现用户账户安全性问题
2.编码转换，可在服务端的过滤器中设置统一的编码格式，避免出现乱码
3.对用户发送的数据进行过滤替换
4.转换图像格式
5.对响应的内容进行压缩
其中，第1,2场景经常涉及。
login.jsp
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<%@ page language="java" import="java.util.*" contenttype="text/html; charset=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 action="<%=path %>/servlet/loginservlet" method="post" > 用户名:<input type="text" name="username" /> 密码:<input type="password" name="password" /> <input type="submit" value="登录" /> </form> </body></html> |
success.jsp
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<%@ page language="java" import="java.util.*" pageencoding="utf-8" contenttype="text/html; charset=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> </body></html> |
failure.jsp
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<%@ page language="java" import="java.util.*" contenttype="text/html; charset=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> 登录失败，请检查用户名或密码！ </body></html> |
loginfilter.java
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package com.cityhuntshou.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 javax.servlet.http.httpservletresponse;import javax.servlet.http.httpsession;public class loginfilter implements filter { private filterconfig config; public void destroy() { } public void dofilter(servletrequest arg0, servletresponse arg1, filterchain arg2) throws ioexception, servletexception { httpservletrequest request = (httpservletrequest) arg0; httpservletresponse response = (httpservletresponse) arg1; httpsession session = request.getsession(); //过滤器实际应用场景之二-----编码转换 string charset = config.getinitparameter("charset"); if(charset == null) { charset = "utf-8"; } request.setcharacterencoding(charset); string nologinpaths = config.getinitparameter("nologinpaths"); if(nologinpaths != null) { string[] strarray = nologinpaths.split(";"); for(int i = 0; i < strarray.length; i++) { //空元素，放行 if(strarray[i] == null || "".equals(strarray[i])) continue; if(request.getrequesturi().indexof(strarray[i]) != -1) { arg2.dofilter(arg0, arg1); return; } } } if(request.getrequesturi().indexof("login.jsp") != -1 || request.getrequesturi().indexof("loginservlet") != -1) { arg2.dofilter(arg0, arg1); return; } if(session.getattribute("username") != null) { arg2.dofilter(arg0, arg1); } else { response.sendredirect("login.jsp"); } } public void init(filterconfig arg0) throws servletexception { config = arg0; }} |
loginservlet.java
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package com.cityhuntshou.servlet;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 { } /** * 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 username = request.getparameter("username"); string password = request.getparameter("password"); //new string(username.getbytes("iso-8859-1"),"utf-8") system.out.println(username); if("admin".equals(username) && "admin".equals(password)) { //校验通过 httpsession session = request.getsession(); session.setattribute("username", username); response.sendredirect(request.getcontextpath()+"/success.jsp"); } else { //校验失败 response.sendredirect(request.getcontextpath()+"/failure.jsp"); } } /** * initialization of the servlet. <br> * * @throws servletexception if an error occurs */ public void init() throws servletexception { // put your code here }} |
web.xml
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<?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"> <display-name></display-name> <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>com.cityhuntshou.servlet.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> <filter> <filter-name>loginfilter</filter-name> <filter-class>com.cityhuntshou.filter.loginfilter</filter-class> <init-param> <param-name>nologinpaths</param-name> <param-value>login.jsp;failure.jsp;loginservlet</param-value> </init-param> <init-param> <param-name>charset</param-name> <param-value>utf-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>loginfilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping></web-app> |
运行效果：
访问结果：
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：http://www.cnblogs.com/cityhuntshou/p/7443688.html
