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【Servlet】Java Servet Filter 过滤器
Filter的设计思想
Filter是一种AOP的设计思想 : 面向切面
下面这是一个使用filter的登录案例：
我们通过一张图片理解理解filer面向切面
下面是项目的结构：
下面是jsp文件：
<%@ 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="login.do" method="POST"><span>用户名：</span><span><input type="text" name="uname" /></span><br/><span>密码：</span><span><input type="password" name="upass" /></span><br/><input type="submit" value="http://www.mamicode.com/提交"/></form></body></html>
下面是web.xml文件：
<?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" version="3.0"> <display-name>Filter_Demo</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> </welcome-file-list> <!-- 设置请求的编码格式的过滤器 --> <filter> <filter-name>request</filter-name> <filter-class>cn.userLogin.filter.RequestFilter</filter-class> </filter> <filter-mapping> <filter-name>request</filter-name> <url-pattern>*.do</url-pattern> </filter-mapping> <!-- 设置响应的编码格式的过滤器 --> <filter> <filter-name>response</filter-name> <filter-class>cn.userLogin.filter.ResponseFilter</filter-class> </filter> <filter-mapping> <filter-name>response</filter-name> <url-pattern>*.do</url-pattern> </filter-mapping> <!-- 设置检查参数的格式编码器 --> <filter> <filter-name>param</filter-name> <filter-class>cn.userLogin.filter.ParamFilter</filter-class> </filter> <filter-mapping> <filter-name>param</filter-name> <url-pattern>*.do</url-pattern> </filter-mapping> </web-app>
下面是servelet文件
package cn.user.servlet;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class UserLogin */@WebServlet("/login.do")public class UserLogin extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //进行数据判断 String userName=request.getParameter("uname"); String userPassword=request.getParameter("upass"); //从数据库中查询相应的信息... //将信息返回 response.getWriter().append("姓名："+userName+",密码："+userPassword); }}
下面是filter文件：
package cn.userLogin.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.annotation.WebFilter;/** * 这个过滤器设置请求的编码格式 */public class RequestFilter implements Filter { public void destroy() { // TODO Auto-generated method stub } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //设置请求的编码格式 request.setCharacterEncoding("utf-8"); //放行 chain.doFilter(request, response); } public void init(FilterConfig fConfig) throws ServletException { }}
package cn.userLogin.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;/** * 这个过滤器设置响应的编码格式 */public class ResponseFilter implements Filter { /** * 过滤器销毁的时候调用 */ public void destroy() { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //设置响应的编码格式 response.setContentType("text/html;charset=utf-8"); //放行 chain.doFilter(request, response); } /** * 过滤器初始化的时候调用 */ public void init(FilterConfig fConfig) throws ServletException { }}
package cn.userLogin.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.annotation.WebFilter;/** * 这个过滤器进行参数的格式检查 */public class ParamFilter implements Filter { public void destroy() { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //检查参数的格式 String uName = request.getParameter("uname"); String uPassword = request.getParameter("upass"); if(uName == null || uPassword == null || uName.length()==0 || uPassword.length()==0){ response.getWriter().append("你的参数格式不正常"); return;//退出方法 } chain.doFilter(request, response); } /** * @see Filter#init(FilterConfig) */ public void init(FilterConfig fConfig) throws ServletException { // TODO Auto-generated method stub }}
【Servlet】Java Servet Filter 过滤器
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