【Servlet】Java Servet Filter 過濾器
阿新 • • 發佈：2017-06-28
退出方法 efi rlogin file submit ati 姓名 ner lan 
Filter的設計思想
Filter是一種AOP的設計思想 : 面向切面
下面這是一個使用filter的登錄案例：
我們通過一張圖片理解理解filer面向切面
下面是項目的結構：
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>用戶名：</span><span><input type="text" name="uname" /></span><br/>
<span>密碼：</span><span><input type="password" name="upass" /></span><br/>
<input type="submit" value="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>
<!-- 設置請求的編碼格式的過濾器 -->
<filter>
<filter-name>request</filter-name>
<filter-class
web.xml
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 { //進行數據判斷 String userName=request.getParameter("uname"); String userPassword=request.getParameter("upass"); //從數據庫中查詢相應的信息... //將信息返回 response.getWriter().append("姓名："+userName+",密碼："+userPassword); } }UserLogin.java
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; /** * 這個過濾器設置請求的編碼格式 */ 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 { //設置請求的編碼格式 request.setCharacterEncoding("utf-8"); //放行 chain.doFilter(request, response); } public void init(FilterConfig fConfig) throws ServletException { } }RequestFilter.java
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; /** * 這個過濾器設置響應的編碼格式 */ public class ResponseFilter implements Filter { /** * 過濾器銷毀的時候調用 */ public void destroy() { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //設置響應的編碼格式 response.setContentType("text/html;charset=utf-8"); //放行 chain.doFilter(request, response); } /** * 過濾器初始化的時候調用 */ public void init(FilterConfig fConfig) throws ServletException { } }ResponseFilter.java
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; /** * 這個過濾器進行參數的格式檢查 */ public class ParamFilter implements Filter { public void destroy() { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //檢查參數的格式 String uName = request.getParameter("uname"); String uPassword = request.getParameter("upass"); if(uName == null || uPassword == null || uName.length()==0 || uPassword.length()==0){ response.getWriter().append("你的參數格式不正常"); 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 } }ParamFilter.java
【Servlet】Java Servet Filter 過濾器