java--过滤器
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CharacterFilter
package cn.hncu.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;
/*
* 过滤器开发:
* 1.写一个类实现Filter接口
* 2.配置web.xml (配置<filter>和<filter-mapping>两个元素)
*
*/
public class CharacterFilter implements Filter
private String charset;
//过滤器的init在服务器一启动时就会执行。
//servlet如果配置了load-on-startup选项则也会在服务器启动
//时就执行初始化，否则只有在第一次访问该servlet时才会执行。
@Override
public void init(FilterConfig filterConfig) throws ServletException
System.out.println("CharacterFilter-init...");
this.charset=filterConfig.getInitParameter("charset");
@Override//该方法在拦截到相应请求或响应时才会执行
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException
System.out.println("CharacterFilter-doFilter...拦截请求");//拦截请求
//request.setCharacterEncoding("utf-8");//编码写死了
request.setCharacterEncoding(charset);
//编码写活，让用户可配置(在web.xml中修改参数)
chain.doFilter(request, response);//放行
System.out.println("CharacterFilter-doFilter...拦截响应");//拦截响应
response.setContentType("text/html;charset="+charset);
@Override
public void destroy()
System.out.println("CharacterFilter-destory...");
LoginSecureFilter
package cn.hncu.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;
public class LoginSecureFilter implements Filter
@Override
public void init(FilterConfig filterConfig) throws ServletException
System.out.println("LoginSecureFilter-init...");
@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException
System.out.println("LoginSecureFilter-doFilter...拦截请求");//拦截请求
HttpServletRequest req=(HttpServletRequest) request;
String name=(String) req.getSession().getAttribute("name");
if(name==null||name.trim().equals(""))
//踢到登录页面
//注意，重定向时路径中的第一个"/"是指Tomcat的根目录，因此这里必须加一个项目名。
((HttpServletResponse)response).sendRedirect(req.getContextPath()+"/index.jsp");
chain.doFilter(request, response);//放行
System.out.println("LoginSecureFilter-doFilter...拦截响应");//拦截响应
@Override
public void destroy()
web.xml–配置Filter和Servlet
<?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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
<display-name></display-name>
<!-- 过滤器链中，这一段的配置顺序决定init的执行顺序 -->
<filter>
<filter-name>login</filter-name>
<filter-class>cn.hncu.filter.LoginSecureFilter</filter-class>
</filter>
<filter>
<filter-name>three</filter-name>
<filter-class>cn.hncu.filter.CharacterFilter</filter-class>
<init-param>
<param-name>charset</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<!-- 拦截路径设置说明:
1. “/*” 表示拦截所有资源
2. “*.jsp” 表示拦截所有jsp页面的请求与响应
3. “/jsps/*.jsp” ※不能这样写，格式错误※
4. “/jsps/*” 表示拦截jsps目录下的所有资源
5. “/LoginServlet” 表示只拦截映射路径为“/LoginServlet”的这一个servlet
6. “login” 表示只拦截名“login”的servlet(可以把jsp页面配置成serlvet)
-->
<!-- 过滤器链中，这一段的配置顺序决定拦截顺序(过滤器的过滤顺序) -->
<filter-mapping>
<filter-name>three</filter-name>
<!-- 指定拦截访问后台的哪些资源(servlet,jsp,jpg文件等), '/*'代表所有资源 -->
<url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>cn.hncu.servlet.LoginServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>BuyServlet1</servlet-name>
<servlet-class>cn.hncu.servlet.BuyServlet1</servlet-class>
</servlet>
<servlet>
<servlet-name>BuyServlet2</servlet-name>
<servlet-class>cn.hncu.servlet.BuyServlet2</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>BuyServlet1</servlet-name>
<url-pattern>/buy/buy1</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>BuyServlet2</servlet-name>
<url-pattern>/buy/buy2</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>初始化顺序
主页面index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<body>
<h2>这是主页...OKOK</h2>
<c:url value="/login"/>
<form action='<c:url value="/login"/>' method="post">
姓名:<input type="text" name="name"/><br/>
<input type="submit" value="提交">
</form>
<a href='<c:url value="/buy/buy1"/>'>商品1</a>
<a href='<c:url value="/buy/buy2"/>'>商品2</a>
<a href='<c:url value="/jsps/a.jsp"/>'>欢迎</a>
</body>
</html>
/jsps/wel.jsp–登录成功页面
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<body>
<h2>这是欢迎页面</h2>
欢迎你,$name!
</body>
</html>
/jsps/a.jsp–欢迎页面
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<body>
<h2>很多贵宾才能看到的商品</h2>
欢迎你,$name! <br/>
<img src="<c:url value='/imgs/1.png'/>" />
</body>
</html>
LoginServlet–登录，未被LoginSecureFilter拦截
package cn.hncu.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
doPost(request, response);
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
String name=request.getParameter("name");
//....//省略若干行代码(调用service及dao层，到数据库中验证身份)
request.getSession().setAttribute("name", name);//这里假设验证成功
System.out.println(request.getContextPath()+"/jsps/wel.jsp");
response.sendRedirect(request.getContextPath()+"/jsps/wel.jsp");
// response.sendRedirect(request.getContextPath()+"/index.jsp");
BuyServlet1–BuyServlet2同（映射路径为”/buy/buy1”和“/buy/buy2”）
package cn.hncu.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;
public class BuyServlet1 extends HttpServlet
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
doPost(request, response);
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
String name = request.getParameter("name");
PrintWriter p=response.getWriter();
p.print(name+"访问了buy1");
p.print("进行购物---调用service层的相应逻辑");//要求必须登录过后才能访问该模块
第一次访问主页的filter拦截
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