filter过滤器登录验证

1.新建一个FirstFilter类代码如下:

package com.ask.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.HttpServletResponse;

/*自定义一个java类实现filter接口*/

public class FirstFilter implements Filter {

//通过file配置文件中修改编码方式;

private FilterConfig config;

public FirstFilter(){

System.out.println("FirstFilter: "+this.hashCode());

}

public void init(FilterConfig arg0) throws ServletException {

config=arg0;

System.out.println("init: "+this.hashCode());

}

public void doFilter(ServletRequest req, ServletResponse res,

FilterChain chain) throws IOException, ServletException {

String utf8=config.getInitParameter("utf-8");

HttpServletResponse resp=(HttpServletResponse) res;

//resp.setContentType("text/html;charset=utf-8");

resp.setContentType("text/html;charset="+utf8);

//调用下一个filter或者是web资源

chain.doFilter(req, res);

}

public void destroy() {

System.out.println("destroy: "+this.hashCode());

}

}

2.新建一个LoginFilter类代码如下：

packagecom.ask.filter;

importjava.io.IOException;

importjavax.servlet.Filter;

importjavax.servlet.FilterChain;

importjavax.servlet.FilterConfig;

importjavax.servlet.ServletException;

importjavax.servlet.ServletRequest;

importjavax.servlet.ServletResponse;

importjavax.servlet.http.HttpServletRequest;

importjavax.servlet.http.HttpServletResponse;

importjavax.servlet.http.HttpSession;

publicclassLoginFilterimplementsFilter {

publicvoiddoFilter(ServletRequest arg0, ServletResponse arg1,

FilterChain chain)throwsIOException, ServletException {

HttpServletRequest req=(HttpServletRequest) arg0;

HttpServletResponse res=(HttpServletResponse) arg1;

//获取资源路径;

String uri=req.getRequestURI();

//获得jsp文件名;

String action=uri.substring(uri.lastIndexOf("/")+1, uri.indexOf("."));

System.out.println(action);

if("login".equals(action)&&uri.endsWith(".jsp")) {//判断是否是longin.jsp请求

chain.doFilter(req, res);

}else{//main.jsp longin.do

if("login".equals(action)) {//如果是login.do请求

HttpSession session=req.getSession();

if(session.getAttribute("name")==null) {

String name=req.getParameter("username");

String pwd=req.getParameter("password");

if("tom".equals(name)&&"123".equals(pwd)) {

session.setAttribute("name", name);

chain.doFilter(req, res);

}else{

res.sendRedirect(req.getContextPath()+"/login.jsp");

}

}

}else{

HttpSession session=req.getSession(false);

if(session.getAttribute("name")==null) {

res.sendRedirect(req.getContextPath()+"/login.jsp");

}else{

chain.doFilter(req, res);

}

}

}

}

publicvoidinit(FilterConfig arg0)throwsServletException {

//TODOAuto-generated method stub

}

publicvoiddestroy() {

//TODOAuto-generated method stub

}

}

3.新建一个SecFilter类，代码如下：

package com.ask.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;

public class SecFilter implements Filter {

public void destroy() {

System.out.println("sec---destroy");

}

public void doFilter(ServletRequest req, ServletResponse res,

FilterChain chain) throws IOException, ServletException {

chain.doFilter(req, res);

}

public void init(FilterConfig arg0) throws ServletException {

System.out.println("sec---init");

}

}

4.新建一个showServlet类代码如下:

package com.ask.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 javax.servlet.http.HttpSession;

public class showServlet extends HttpServlet {

@Override

protected void service(HttpServletRequest req, HttpServletResponse res)

throws ServletException, IOException {

String name=req.getParameter("username");

System.out.println("service");

res.getWriter().write("演示servlet中的filter过滤器");

HttpSession session=req.getSession();

session.setAttribute("name", name);

System.out.println("登录成功");

res.sendRedirect(req.getContextPath()+"/main.jsp");

}

}

5.在WebRoot目录下新建两个jsp文件，分别是login.jsp和main.jsp文件

Login.jsp如下

<%@ page language="java"contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type"content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

<form action="${pageContext.request.contextPath }/login.do"method="post">

username:<input type="text"name="username">

password:<input type="password"name="password">

<input type="submit"value="longing">

</form>

</body>

</html>

Main.jsp如下:

<%@ page language="java"contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type"content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

欢迎 ${name}进入主页面

</body>

</html>

6.在web.xml配置文件中配置如下:

<?xml version="1.0"encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns="http://java.sun.com/xml/ns/javaee"xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"id="WebApp_ID"version="3.0">

<display-name>firstServlet</display-name>

<welcome-file-list>

<welcome-file>index.html</welcome-file>

<welcome-file>index.htm</welcome-file>

<welcome-file>index.jsp</welcome-file>

<welcome-file>default.html</welcome-file>

<welcome-file>default.htm</welcome-file>

<welcome-file>default.jsp</welcome-file>

</welcome-file-list>

<!-- 测试LoginFilter -->

<filter>

<filter-name>first</filter-name>

<filter-class>com.ask.filter.LoginFilter</filter-class>

</filter>

<filter-mapping>

<filter-name>first</filter-name>

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

</filter-mapping>

<servlet>

<servlet-name>show</servlet-name>

<servlet-class>com.ask.servlet.showServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>show</servlet-name>

<url-pattern>*.do</url-pattern>

</servlet-mapping>

</web-app>