过滤器
Posted 滥好人
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了过滤器相关的知识，希望对你有一定的参考价值。
做过滤器：
一、做类
建一个实现javax.servlet.Filter接口的类
在doFilter()方法中编写过滤逻辑
二、做配置
在web.xml中配置<filter>和<filter-mapping>元素
例一：
验证页面是否登录，没登录跳转到登录页面。
1.建一个实现javax.servlet.Filter接口的类
2.在doFilter()方法中编写过滤逻辑
package com.itnba.maya.filter; import java.io.IOException; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public class StateFilter implements Filter { private ArrayList<String> list =new ArrayList<String>();//建一个集合，放可以不用验证身份的页面 @Override public void destroy() { // TODO 自动生成的方法存根 } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //转换类型 HttpServletRequest req=(HttpServletRequest) request; HttpServletResponse res=(HttpServletResponse) response;
req.setCharacterEncoding("utf-8");
res.setCharacterEncoding("utf-8");
HttpSession session=req.getSession(); //获取请求界面的路径 String a=req.getRequestURI();//长的路径 String b=req.getContextPath();//短的路径 String c=a.substring(b.length());//截取路径 if(list.contains(c)==false){ //要请求的不是登录页面，需要验证session; if(session.getAttribute("user")==null){//判断session是否有值，没有就转到登录页面 res.sendRedirect("cs1.jsp"); } else{ chain.doFilter(req, res); } } else{ chain.doFilter(req, res); } } @Override public void init(FilterConfig arg0) throws ServletException { String val=arg0.getInitParameter("allowpage");//读web.xml配置中的init-param的value //劈开放到数组中 String[]arr =val.split(","); //把数组全部放到集合里 list.addAll(Arrays.asList(arr)); } }
3.在web.xml中配置<filter>和<filter-mapping>元素
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1"> <filter> <filter-name>statefilter</filter-name><!--自己取的名字，跟下面的要一样--> <filter-class>com.itnba.maya.filter.StateFilter</filter-class><!--过滤器类的包名和类名--!> <init-param> <param-name>allowpage</param-name><!--在过滤器类中的 init(FilterConfig arg0)方法调用，获取下面的value值--!> <param-value>/cs1.jsp,/Cs1</param-value> </init-param> </filter> <filter-mapping> <filter-name>statefilter</filter-name><!--自己取的名字，跟上面的要一样--> <url-pattern>/*</url-pattern><!--要过滤的页面/*代表全部--> </filter-mapping> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
这样运行没有登录的页面，就会跳转到登录页面。
例二：
过滤敏感词，替换成***
1.建一个实现javax.servlet.Filter接口的类
2.在doFilter()方法中编写过滤逻辑，需要用内部类自己定义一request
package com.itnba.maya.filter; import java.io.IOException; import java.util.ArrayList; import java.util.Arrays; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletRequestWrapper; import javax.servlet.http.HttpServletResponse; public class Filter implements javax.servlet.Filter { private ArrayList<String> list =new ArrayList<>(); @Override public void destroy() { // TODO 自动生成的方法存根 } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { HttpServletRequest req=(HttpServletRequest) request; HttpServletResponse res=(HttpServletResponse) response; HttpServletRequest mreq=new MyRequest(req); //向下一个链条放行,不能用原来的request; chain.doFilter(mreq, res); } @Override public void init(FilterConfig arg0) throws ServletException { //把敏感词放到集合里 String val=arg0.getInitParameter("minganci"); String[] ss = val.split(","); list.addAll(Arrays.asList(ss)); } //内部类，自己定义request class MyRequest extends HttpServletRequestWrapper{ private HttpServletRequest request; public MyRequest(HttpServletRequest request) { super(request); this.request=request; } @Override //重写getParameter public String getParameter(String name) { //获取提交内容 String txt=this.request.getParameter("txt"); //改集合里的敏感词 for(String s:list){ txt=txt.replaceAll(s, "***"); } return txt; } } }
3.在web.xml中配置<filter>和<filter-mapping>元素
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1"> <filter> <filter-name>Filter</filter-name> <filter-class>com.itnba.maya.filter.Filter</filter-class><!--过滤器类的包名和类名--!> <init-param> <param-name>minganci</param-name><!--在过滤器类中的 init(FilterConfig arg0)方法调用，获取下面的value值--!> <param-value>sb,cnm,tmd</param-value> </init-param> </filter> <filter-mapping> <filter-name>Filter</filter-name> <url-pattern>/*</url-pattern><!--要过滤的页面/*代表全部--> </filter-mapping> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
jsp页面
<%@ 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="test.jsp" method="post"> <textarea name="txt" rows="5" cols="10"> sbdfdsfscnmdfdsfsdtmdfdsfsdfcnmsbtmd </textarea> <input type="submit" value="提交"> </form> </body> </html>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!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=ISO-8859-1"> <title>Insert title here</title> </head> <body> ${param.txt } </body> </html>
敏感词汇都变成了***
以上是关于过滤器的主要内容，如果未能解决你的问题，请参考以下文章