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文章目录
1.基本介绍1.为什么需要过滤器？2.基本介绍3.过滤器的基本原理 2.快速入门1.文件目录2.环境配置创建maven项目，导入依赖 3.代码实现1.login.jsp2.LoginCheck.java3.ManagerFilter.java编写过滤规则4.配置web.xml告诉tomcat5.admin.jsp 3.Filter的执行流程1.服务器启动2.请求匹配3.细节说明 4.url-pattern5.Filter生命周期6.FilterConfig1.基本介绍2.代码演示1.FilterConfig.java2.web.xml5.结果 3.课后练习1.FilterConfig.java2.结果 7.FilterChain1.基本原理2. 代码实例1.AFilter.java2.BFilter.java3.web.xml4.结果 3.注意事项 8.作业练习1.homeworkFilter.java2.web.xml3.topic.jsp4.showTopic.jsp5.演示结果
1.基本介绍
1.为什么需要过滤器？
2.基本介绍
3.过滤器的基本原理
2.快速入门
1.文件目录
2.环境配置
创建maven项目，导入依赖
<dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> <dependency> <groupId>javax.servlet.jsp</groupId> <artifactId>jsp-api</artifactId> <version>2.2</version> <scope>provided</scope> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.1.0</version> </dependency> <dependency> <groupId>org.apache.taglibs</groupId> <artifactId>taglibs-standard-impl</artifactId> <version>1.2.5</version> <scope>runtime</scope> </dependency> <dependency> <groupId>org.apache.taglibs</groupId> <artifactId>taglibs-standard-spec</artifactId> <version>1.2.5</version> </dependency> </dependencies>
3.代码实现
1.login.jsp
<%-- Date: 2024/1/31 Time: 13:34 User: 孙显圣 Version:1.0--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head> <title>Title</title></head><body><form action="<%=request.getContextPath()%>/loginCheck" method="post"> username:<input type="text" name="username"><br> password:<input type="password" name="password"><br> <input type="submit" value="提交"></form></body></html>
2.LoginCheck.java
package servlet;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;import java.io.IOException;/** * @author 孙显圣 * @version 1.0 * 验证信息是否正确，如果正确则设置session */@WebServlet(urlPatterns = "/loginCheck")public class LoginCheck extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String username = req.getParameter("username"); String password = req.getParameter("password"); if ("666666".equals(password)) { //设置session HttpSession session = req.getSession(); session.setAttribute("name", username); req.getRequestDispatcher("manager/admin.jsp").forward(req, resp); } else { //不合法直接返回登录界面 req.getRequestDispatcher("login.jsp").forward(req, resp); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); }}
3.ManagerFilter.java编写过滤规则
package filter;import javax.servlet.*;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpSession;import java.io.IOException;/** * @author 孙显圣 * @version 1.0 */public class ManagerFilter implements Filter { public void init(FilterConfig filterConfig) throws ServletException { //当filter创建后会调用这个方法初始化 System.out.println("初始化"); } public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { //每次调用该filter时该方法就会被调用 //检查是否有session,将servletRequest向下转型为httpServletRequest HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest; HttpSession session = httpServletRequest.getSession(); //获取session中的name Object name = session.getAttribute("name"); if (name != null) { //继续访问目标资源 filterChain.doFilter(servletRequest,servletResponse); } else { httpServletRequest.getRequestDispatcher("/login.jsp").forward(servletRequest,servletResponse); } } public void destroy() { //filter被销毁时会调用 System.out.println("destroy"); }}
4.配置web.xml告诉tomcat
<?xml version="1.0" encoding="UTF-8"?><web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaeehttp://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <display-name>Archetype Created Web Application</display-name><!-- filter一般写在最前面 --><!-- url-pattern就是当请求的url与之匹配的时候tomcat就会调用filter--><!-- /manager/*指的就是manager下面所有的资源--><filter> <filter-name>ManagerFilter</filter-name> <filter-class>filter.ManagerFilter</filter-class></filter><filter-mapping> <filter-name>ManagerFilter</filter-name> <url-pattern>/manager/*</url-pattern></filter-mapping></web-app>
5.admin.jsp
<%-- Date: 2024/1/31 Time: 13:37 User: 孙显圣 Version:1.0--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head> <title>Title</title> <base href="<%=request.getContextPath()%>/manager/"></head><body><h1 align="center"> 管理员界面</h1><img src="1.png" height="600" border="1"></body></html>
3.Filter的执行流程
1.服务器启动
读取web.xml
根据全类名反射创建过滤器的实例，将其放在name - 实例的容器中，并将url - name容器也填充一共有两个容器 url - namename - 实例 创建FilterConfig对象，调用 init(FilterConfig filterConfi g)方法初始化过滤器
2.请求匹配
遍历a容器，匹配url如果匹配到，则找到里面的name，并且遍历b容器，根据name找到filter实例调用doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)方法
3.细节说明
过滤器起到一个浏览器请求拦截的作用，请求转发不经过过滤器过滤器实例只有一个一旦匹配到过滤器，过滤器只要不做任何操作，就会卡在这个页面，并不会继续匹配servlet除非过滤器调用filterChain.doFilter(servletRequest, servletResponse)才会放行过滤器里面的servletRequest和servletResponse是httpServletRequest和httpServletResponse的父类，可以向下转型
4.url-pattern
5.Filter生命周期
6.FilterConfig
1.基本介绍
2.代码演示
1.FilterConfig.java
package filter;import javax.servlet.*;import java.io.IOException;import java.util.Enumeration;/** * @author 孙显圣 * @version 1.0 */public class FilterConfig implements Filter { public void init(javax.servlet.FilterConfig filterConfig) throws ServletException { //通过filterConfig获取相关的参数 //1.获取filter的名字 String filterName = filterConfig.getFilterName(); System.out.println("filterName: " + filterName); //2.获取filter配置参数 String ip = filterConfig.getInitParameter("ip"); System.out.println("ip: " + ip); //3.获取filter的所有配置参数的名字 Enumeration<String> initParameterNames = filterConfig.getInitParameterNames(); while (initParameterNames.hasMoreElements()){ System.out.println("filterNames: " + initParameterNames.nextElement()); } //4.获取servletContext ServletContext servletContext = filterConfig.getServletContext(); System.out.println("servletContext: " + servletContext); } public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { } public void destroy() { }}
2.web.xml
<filter> <filter-name>filterConfig</filter-name> <filter-class>filter.FilterConfig</filter-class> <!--配置参数--> <init-param> <param-name>ip</param-name> <param-value>12.344.123.12</param-value> </init-param> <init-param> <param-name>qq</param-name> <param-value>1721469477@qq.com</param-value> </init-param> </filter> <filter-mapping> <filter-name>filterConfig</filter-name> <url-pattern>/abc/*</url-pattern> </filter-mapping>
5.结果
3.课后练习
1.FilterConfig.java
package filter;import javax.servlet.*;import javax.servlet.http.HttpServletRequest;import java.io.IOException;/** * @author 孙显圣 * @version 1.0 */public class FilterConfig implements Filter { public void init(javax.servlet.FilterConfig filterConfig) throws ServletException { //获取filter配置参数 String ip = filterConfig.getInitParameter("ip"); //获取servletContext ServletContext servletContext = filterConfig.getServletContext(); //把禁用的网段放入servletContext servletContext.setAttribute("ip", ip); } public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { ServletContext servletContext = servletRequest.getServletContext(); Object ip = servletContext.getAttribute("ip"); if (ip != null) { String ip_ = (String) ip; //获取禁用网段ip } HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest; //获取请求的ip String remoteAddr = httpServletRequest.getRemoteAddr(); //使用正则表达式匹配 String regStr = ip + ".*"; if (!remoteAddr.matches(regStr)) { //如果不是禁用网段跳转到登录页面 httpServletRequest.getRequestDispatcher("/login.jsp").forward(servletRequest,servletResponse); } } public void destroy() { }}
2.结果
7.FilterChain
1.基本原理
2. 代码实例
1.AFilter.java
package filter;import javax.servlet.*;import javax.servlet.FilterConfig;import java.io.IOException;/** * @author 孙显圣 * @version 1.0 */public class AFilter implements Filter { public void init(FilterConfig filterConfig) throws ServletException { } public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println("AFilter的前置代码"); filterChain.doFilter(servletRequest,servletResponse); System.out.println("AFilter的后置代码"); } public void destroy() { }}
2.BFilter.java
package filter;import javax.servlet.*;import javax.servlet.FilterConfig;import java.io.IOException;/** * @author 孙显圣 * @version 1.0 */public class BFilter implements Filter { public void init(FilterConfig filterConfig) throws ServletException { } public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println("BFilter的前置代码"); filterChain.doFilter(servletRequest,servletResponse); System.out.println("BFilter的后置代码"); } public void destroy() { }}
3.web.xml
<filter> <filter-name>A</filter-name> <filter-class>filter.AFilter</filter-class> </filter> <filter-mapping> <filter-name>A</filter-name> <url-pattern>/aaa</url-pattern> </filter-mapping> <filter> <filter-name>B</filter-name> <filter-class>filter.BFilter</filter-class> </filter> <filter-mapping> <filter-name>B</filter-name> <url-pattern>/aaa</url-pattern> </filter-mapping>
4.结果
3.注意事项
8.作业练习
1.homeworkFilter.java
package filter;import javax.servlet.*;import javax.servlet.FilterConfig;import javax.servlet.http.HttpServletRequest;import java.io.IOException;import java.util.ArrayList;import java.util.Enumeration;/** * @author 孙显圣 * @version 1.0 */public class homeworkFilter implements Filter { public void init(FilterConfig filterConfig) throws ServletException { //动态获取评论，并将评论都放到servletContext中 ServletContext servletContext = filterConfig.getServletContext(); Enumeration<String> initParameterNames = filterConfig.getInitParameterNames(); ArrayList<String> comments = new ArrayList<String>(); while (initParameterNames.hasMoreElements()) { String s = initParameterNames.nextElement(); String initParameter = filterConfig.getInitParameter(s); comments.add(initParameter); } servletContext.setAttribute("comments", comments); } public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { //获取所有评论 ServletContext servletContext = servletRequest.getServletContext(); Object comments = servletContext.getAttribute("comments"); //获取填写的评论 String comment = servletRequest.getParameter("comment"); //没有禁止的评论就直接放行 if (comments == null) { filterChain.doFilter(servletRequest, servletResponse); } //禁止的评论不为空则遍历判断 ArrayList<String> coms = (ArrayList<String>) comments; for (String com : coms) { //遍历禁用词 if (com.equals(comment)) { //请求转发到主页面并将禁用词传进去 servletRequest.setAttribute("badComment", comment); servletRequest.getRequestDispatcher("/topic.jsp") .forward(servletRequest, servletResponse); } } filterChain.doFilter(servletRequest, servletResponse); } public void destroy() { }}
2.web.xml
<filter> <filter-name>homeworkFilter</filter-name> <filter-class>filter.homeworkFilter</filter-class> <init-param> <param-name>com1</param-name> <param-value>苹果</param-value> </init-param> <init-param> <param-name>com2</param-name> <param-value>香蕉</param-value> </init-param> </filter> <filter-mapping> <filter-name>homeworkFilter</filter-name> <url-pattern>/showTopic.jsp</url-pattern> </filter-mapping>
3.topic.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><%-- Date: 2024/1/31 Time: 17:36 User: 孙显圣 Version:1.0--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head> <title>Title</title></head><body><h4>敏感词：苹果、香蕉 <c:if test="${!empty requestScope.badComment}"> ---有敏感词：${requestScope.badComment} </c:if></h4><form action="showTopic.jsp" method="get"> 评论：<input type="text" name="comment"><br> <input type="submit" value="提交"></form></body></html>
4.showTopic.jsp
<%-- Date: 2024/1/31 Time: 17:39 User: 孙显圣 Version:1.0--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head> <title>Title</title></head><body><h4>您的评论是：<%=request.getParameter("comment")%></h4></body></html>
5.演示结果
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