Day40

Day40

监听器

概念:

监听器用于监听web应用中某些对象信息的创建、销毁、增加,修改,删除等动作的

发生,然后作出相应的响应处理。当范围对象的状态发生变化的时候,服务器自动调用

监听器对象中的方法。

常用于统计在线人数和在线用户,系统加载时进行信息初始化,统计网站的访问量等。

类别:

第一大类:监听请求域、会话域、全局域对象的创建和销毁。

第二大类:监听请求域、会话域、全局域对象的属性的创建、替换、销毁。

第三大类:监听会话域(String key - Object value)里value的绑定和解绑、钝化和活化。

第一大类

监听请求域:

servlet:

java 复制代码
package com.qf.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 java.io.IOException;
@WebServlet("/Servlet01")
public class Servlet01 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("执行Servlet");
    }
}

web.xml:

xml 复制代码
<listener>
        <listener-class>com.qf.listen.MyServletRequestListener</listener-class>
    </listener>

listener:

java 复制代码
package com.qf.listen;

import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;

public class MyServletRequestListener implements ServletRequestListener {
    @Override
    public void requestDestroyed(ServletRequestEvent servletRequestEvent) {
        ServletRequest request = servletRequestEvent.getServletRequest();
        System.out.println("请求对象被销毁了"+request);
    }

    @Override
    public void requestInitialized(ServletRequestEvent servletRequestEvent) {
        ServletRequest request = servletRequestEvent.getServletRequest();
        System.out.println("请求对象被创建了"+request);
    }
}

注:请求对象的生命周期为,创建:客户端发送请求,服务器会创建请求对象。销毁:服务器返回响应后,会把请求对象、响应对象一并销毁。

监听会话域

注意:查看生命周期要把index.jsp改名或者删除,因为项目启动会默认进入index.jsp,会创建会话对象。

web.xml:(手动调整session销毁时间)

xml 复制代码
<listener>
        <listener-class>com.qf.listen.MyHttpSessionListener</listener-class>
    </listener>
    <session-config>
        <session-timeout>1</session-timeout>
    </session-config>

创建一个page01.jsp。

MyHttpSessionListener:

java 复制代码
package com.qf.listen;

import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class MyHttpSessionListener implements HttpSessionListener {
    @Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        HttpSession session = httpSessionEvent.getSession();
        System.out.println("会话对象被创建了"+session.getId());

    }

    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
        System.out.println("会话对象被销毁了");
    }
}

注:会话对象的什么周期,创建:服务器使用到了session->request.getSession();销毁:session对象设置的过期时间到后就会被销毁。

思考1:客户端访问html资源是否会创建会话对象?答:不会

思考2:客户端访问jsp资源会创建会话对象?为什么?答:会,因为jsp里9大内置对象中有session对象。

思考3:session对象创建后,客户端发送下一次请求是为什么能找到之前的session对象?答:因为客户端在cookie中存储了session的id->JSESSIONID

思考4:session对象是存活在服务器中的,默认为30分钟的生命周期,可客户端存储的cookie里的JSESSIONID为会话结束时,也就意味着关闭浏览器后,再也找不到之前存储在服务器中的session对象,那怎么解决?

答:设置cookie中JSESSION的过期时间。

java 复制代码
package com.qf.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;
@WebServlet("/Servlet01")
public class Servlet01 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("Servlet收到请求");
        HttpSession session = request.getSession();
        Cookie cookie = new Cookie("JSESSION",session.getId());
        cookie.setMaxAge(60*30);
        response.addCookie(cookie);
        response.getWriter().println("abc");
    }
}
监听全局域

web.xml:

xml 复制代码
<context-param>
        <param-name>info</param-name>
        <param-value>abc</param-value>
    </context-param>

<listener>
        <listener-class>com.qf.listen.MyServletContextListener</listener-class>
    </listener>

MyServletContextListener:

java 复制代码
package com.qf.listen;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class MyServletContextListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ServletContext servletContext = servletContextEvent.getServletContext();
        String info = servletContext.getInitParameter("info");
        System.out.println("全局对象被创建了"+"--"+info);
        
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        System.out.println("全局对象被销毁了");

    }
}

注:1.生命周期为项目启动时创建,服务器正常关闭时销毁。

经验:应用场景:

监听全局域对象的创建和销毁,而全局域对象在项目启动时创建,就意味着监听器里的初始化方法在项目启动时就会被调用,所以我们可以把项目初始化的工作放在该方法里。在配置文件中context-param里设置初始数据(建议放在最上面),在监听器的初始化方法中可以用getInitParameter()方法获取数据。

第一大类使用案例-统计在线人数

在全局域监听器中创建:

java 复制代码
        servletContext.setAttribute("count",0);

在会话域监听器中统计:

java 复制代码
package com.qf.listen;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class MyHttpSessionListener implements HttpSessionListener {
    @Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        HttpSession session = httpSessionEvent.getSession();
        System.out.println("会话对象被创建了"+session.getId());
        ServletContext servletContext = session.getServletContext();
        int count = (int) servletContext.getAttribute("count");
        count++;
        servletContext.setAttribute("count",count);
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
        System.out.println("会话对象被销毁了");
        HttpSession session = httpSessionEvent.getSession();
        ServletContext servletContext = session.getServletContext();
        int count = (int) servletContext.getAttribute("count");
        count--;
        servletContext.setAttribute("count",count);
    }
}

第二大类

请求属性监听器

MyServletRequestAttributeListener(用注解配置):

java 复制代码
package com.qf.listen02;

import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;
import javax.servlet.annotation.WebListener;

@WebListener
public class MyServletRequestAttributeListener implements ServletRequestAttributeListener {
    @Override
    public void attributeAdded(ServletRequestAttributeEvent servletRequestAttributeEvent) {
        String name = servletRequestAttributeEvent.getName();
        Object value = servletRequestAttributeEvent.getValue();
        System.out.println("请求域对象添加了属性:"+name+"---"+value);
    }

    @Override
    public void attributeRemoved(ServletRequestAttributeEvent servletRequestAttributeEvent) {
        String name = servletRequestAttributeEvent.getName();
        Object value = servletRequestAttributeEvent.getValue();
        System.out.println("请求域对象删除了属性:"+name+"---"+value);
    }

    @Override
    public void attributeReplaced(ServletRequestAttributeEvent servletRequestAttributeEvent) {
        String name = servletRequestAttributeEvent.getName();
        Object value = servletRequestAttributeEvent.getValue();//获取被替换的值
        System.out.println("请求域对象替换了属性:"+name+"---"+value);
    }
}

page.jsp:

jsp 复制代码
<%
    //操作请求域的属性
    request.setAttribute("msg","aaabbbccc");//添加属性
    request.setAttribute("msg","bbbcccddd");//替换属性
    request.removeAttribute("msg");//删除属性
%>

会话属性监听器

MyHttpSessionAttributeListener:

java 复制代码
package com.qf.listen02;

import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;

public class MyHttpSessionAttributeListener implements HttpSessionAttributeListener {
    @Override
    public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {
        String name = httpSessionBindingEvent.getName();
        Object value = httpSessionBindingEvent.getValue();
        System.out.println("会话域对象添加了属性");
    }

    @Override
    public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {
        String name = httpSessionBindingEvent.getName();
        Object value = httpSessionBindingEvent.getValue();
        System.out.println("会话域对象删除了属性");
    }

    @Override
    public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {
        String name = httpSessionBindingEvent.getName();
        Object value = httpSessionBindingEvent.getValue();
        System.out.println("会话域对象替换了属性");
    }
}

page02.jsp:

jsp 复制代码
<%
    //操作会话域的属性
    session.setAttribute("msg","aaabbbccc");//添加属性
    session.setAttribute("msg","bbbcccddd");//替换属性
    session.removeAttribute("msg");//删除属性
%>

全局属性监听器

MyServletContextAttributeListener:

java 复制代码
package com.qf.listen02;

import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;

public class MyServletContextAttributeListener implements ServletContextAttributeListener {
    @Override
    public void attributeAdded(ServletContextAttributeEvent servletContextAttributeEvent) {
        String name = servletContextAttributeEvent.getName();
        Object value = servletContextAttributeEvent.getValue();
        System.out.println("全局对象创建了属性:"+"--"+name+"--"+value);
    }

    @Override
    public void attributeRemoved(ServletContextAttributeEvent servletContextAttributeEvent) {
        String name = servletContextAttributeEvent.getName();
        Object value = servletContextAttributeEvent.getValue();
        System.out.println("全局对象创建了属性:"+"--"+name+"--"+value);
    }

    @Override
    public void attributeReplaced(ServletContextAttributeEvent servletContextAttributeEvent) {
        String name = servletContextAttributeEvent.getName();
        Object value = servletContextAttributeEvent.getValue();
        System.out.println("全局对象创建了属性:"+"--"+name+"--"+value);
    }
}

page03.jsp:

jsp 复制代码
<%
  //操作全局域的属性
  application.setAttribute("msg","aaabbbccc");//添加属性
  application.setAttribute("msg","bbbcccddd");//替换属性
  application.removeAttribute("msg");//删除属性
%>

第三大类

HttpSessionBindingListener:监听JavaBean对象在session中的绑定(添加)和解绑(删除),即监听某一个具体的类对象,第二大类是监听所有的类对象。

HttpSessionActivationListener:监听JavaBean对象在session中的钝化(序列化)和活化(反序列化)

User:(实现HttpSessionBindingListener,HttpSessionActivationListener,Serializable)

java 复制代码
package com.qf.listen03;

import javax.servlet.http.HttpSessionActivationListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;
import javax.servlet.http.HttpSessionEvent;
import java.io.Serializable;

public class User implements HttpSessionBindingListener, HttpSessionActivationListener, Serializable {
    private String username;
    private String password;
    private String name;
    private String nickName;

    public User(String username, String password, String name, String nickName) {
        this.username = username;
        this.password = password;
        this.name = name;
        this.nickName = nickName;
    }

    public User() {
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName;
    }

    @Override
    public String toString() {
        return "User{" +
                "username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", name='" + name + '\'' +
                ", nickName='" + nickName + '\'' +
                '}';
    }

    @Override
    public void sessionWillPassivate(HttpSessionEvent httpSessionEvent) {
        System.out.println(this+"被session钝化了");
    }

    @Override
    public void sessionDidActivate(HttpSessionEvent httpSessionEvent) {
        System.out.println(this+"被session活化了");
    }

    @Override
    public void valueBound(HttpSessionBindingEvent httpSessionBindingEvent) {
        System.out.println(this+"绑定到session中了");
    }

    @Override
    public void valueUnbound(HttpSessionBindingEvent httpSessionBindingEvent) {
        System.out.println(this+"从session中解绑了");
    }
}

在web里面创建META-INF文件夹,写一个context.xml:

xml 复制代码
<?xml version="1.0" encoding="UTF-8"?>
<Context>
    <Manager className="org.apache.catalina.session.PersistentManager" maxIdleSwap="1">
            <Store className="org.apache.catalina.session.FileStore" directory="C:\\text"/>
    </Manager>
</Context>

Servlet02:

java 复制代码
package com.qf.servlet;

import com.qf.listen03.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
@WebServlet("/Servlet02")
public class Servlet02 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("Servlet02接收到请求了...");
        HttpSession session = request.getSession();
        //注意:将user对象添加到session中,可以叫做User对象绑定到session中 --- 绑定
        session.setAttribute("user",new User("1233211234567","123132","zs","fwkt"));
        //注意:将user对象从session中删除,可以叫做User对象从session中解绑了 --- 解绑
        session.removeAttribute("user");
    }
}

Servlet03:

java 复制代码
package com.qf.servlet;

import com.qf.listen03.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/Servlet03")
public class Servlet03 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("Servlet03接收到请求了...");
        HttpSession session = request.getSession();
        session.setAttribute("user",new User("1233211234567","123132","zs","fwkt"));
    }
}

注意:将User对象添加到session中,可以叫做User对象绑定到session中 --- 绑定

将User对象从session中删除,可以叫做User对象从session中解绑 --- 解绑
面试题:session的钝化与活化:

过滤器

简介

Filter:过滤器,拦截访问web资源的请求与响应操作

Servlet API中提供了Filter接口,开发web应用时,如果编写的Java类实现了这个接口,则把这个Java类称之为过滤器。

创建与使用


场景:welcome.html向Servlet01发送请求:

java 复制代码
package com.qf.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 java.io.IOException;
@WebServlet("/Servlet01.action")
public class Servlet01 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        System.out.println("Servlet收到请求了");
    }
}

过滤器:

java 复制代码
package com.qf.filter;

import javax.servlet.*;
import java.io.IOException;

public class Filter01 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("Filter01 --- init()");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("Filter01 --- doFilter() -- 放行前");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("Filter01 --- doFilter() -- 放行后");


    }

    @Override
    public void destroy() {
        System.out.println("Filter01 --- destroy()");
    }
}

配置文件:

xml 复制代码
<welcome-file-list>
        <welcome-file>welcome.html</welcome-file>
    </welcome-file-list>
    <filter>
        <filter-name>Filter01</filter-name>
        <filter-class>com.qf.filter.Filter01</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Filter01</filter-name>
        <url-pattern>*.action</url-pattern>
    </filter-mapping>

生命周期

创建:项目启动时创建 -- 构造方法、init()

销毁:项目正常关闭时销毁 -- destroy()

注意:Filter对象是单例的。

当有多个过滤器时,

配置文件:

xml 复制代码
<filter>
        <filter-name>Filter01</filter-name>
        <filter-class>com.qf.filter.Filter01</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Filter01</filter-name>
        <url-pattern>*.action</url-pattern>
    </filter-mapping>
    <filter>
        <filter-name>Filter02</filter-name>
        <filter-class>com.qf.filter.Filter01</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Filter02</filter-name>
        <url-pattern>*.action</url-pattern>
    </filter-mapping>
    <filter>
        <filter-name>Filter03</filter-name>
        <filter-class>com.qf.filter.Filter01</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Filter03</filter-name>
        <url-pattern>*.action</url-pattern>
    </filter-mapping>

思考:多个Filter的创建顺序?多个Filter调用顺序?

创建顺序:无序,底层是多线程抢资源。调用顺序为web.xml里的配置顺序(推荐)。如果是使用注解配置,是按照类名字典排序。

案例1 编码过滤器

WEB-学生管理系统中写一个Encoderfilter类进行编码过滤(就不必在servlet中设置了)

配置文件(标准写法要求匹配所有的action,但是由于之前项目中servlet后没有加.action,故此处偷懒直接写/*):

xml 复制代码
<welcome-file-list>
        <welcome-file>welcome.html</welcome-file>
    </welcome-file-list>
    <filter>
        <filter-name>EncoderFilter</filter-name>
        <filter-class>com.qf.filter.EncoderFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>EncoderFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

过滤器:

java 复制代码
package com.qf.filter;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class EncoderFilter implements Filter {
    private String code;
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        code = filterConfig.getInitParameter("code");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        request.setCharacterEncoding(code);
        response.setContentType("text/html;charset="+code);
        filterChain.doFilter(request,response);
    }

    @Override
    public void destroy() {

    }
}
案例2 登录权限过滤器

写一个LoginFilter。

配置文件:

xml 复制代码
<filter>
        <filter-name>LoginFilter</filter-name>
        <filter-class>com.qf.filter.LoginFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>LoginFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

LoginFilter:

java 复制代码
package com.qf.filter;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

public class LoginFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        String requestURI = request.getRequestURI();
        System.out.println(requestURI);
//        StringBuffer requestURL = request.getRequestURL();
//        System.out.println(requestURL);
        HttpSession session = request.getSession();
        String username = (String) session.getAttribute("username");
        String role = (String) session.getAttribute("role");
        String name = (String) session.getAttribute("name");

        if(requestURI.equals("/Day37_war_exploded/register.jsp")||
                requestURI.equals("/Day37_war_exploded/login.jsp")||
                requestURI.equals("/Day37_war_exploded/CodeServlet")||
                requestURI.equals("/Day37_war_exploded/LoginServlet")||
                requestURI.equals("/Day37_war_exploded/")||
                requestURI.equals("/Day37_war_exploded/welcome.html")
        ){
            filterChain.doFilter(request,response);
        }else{
            if(username!=null&&role!=null&&name!=null){
                if("student".equals(role) && requestURI.contains("QueryAllStuServlet")) {
                    response.sendRedirect("index.jsp");
                }
                else{
                    filterChain.doFilter(request,response);
                    
                }
            }

        }


    }

    @Override
    public void destroy() {

    }
}
案例3 敏感词过滤器

场景:在学生详情页面写一个建议,跳转到proposal.jsp,里面写一个表单,提交到ProposalServlet

jsp 复制代码
<%--
  Created by IntelliJ IDEA.
  User: Gu
  Date: 2024-06-17
  Time: 17:37
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h2>建议</h2>
    <form action="ProposalServlet" method="post">
        建议:<input type="text" name="proposal"/>
        <input type="submit" value="提交"/>
        <button type="button" οnclick="fun01()">返回</button>
    </form>
    <script type="text/javascript">
        function fun01(){
            window.location = "index.jsp";
        }
    </script>
</body>
</html>

ProposalServlet(输出建议):

java 复制代码
package com.qf.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 java.io.IOException;
@WebServlet("/ProposalServlet")
public class ProposalServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String proposal = (String) request.getParameter("proposal");
        response.getWriter().println(proposal);
    }
}

MyHttpServletRequestWrapper包装类,继承HttpServletRequestWrapper类(构造方法、重写getParameter方法):

java 复制代码
package com.qf.pojo;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class MyHttpServletRequestWrapper extends HttpServletRequestWrapper {
    public MyHttpServletRequestWrapper(HttpServletRequest request) {
        super(request);
    }

    @Override
    public String getParameter(String name) {
        String parameter = super.getParameter(name);
        if(parameter!=null){
        	parameter = parameter.replaceAll("<","&lt;");
       	    parameter = parameter.replaceAll(">","&gt;");
        	parameter = parameter.replaceAll("傻逼","**");
        }
        
        return parameter;
    }
}

SensitiveWordsFilter:

java 复制代码
package com.qf.filter;

import com.qf.pojo.MyHttpServletRequestWrapper;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

public class SensitiveWordFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        MyHttpServletRequestWrapper requestWrapper = new MyHttpServletRequestWrapper(request);
        filterChain.doFilter(requestWrapper,servletResponse);
    }

    @Override
    public void destroy() {

    }
}
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