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18-filter实现权限拦截

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18-filter实现权限拦截

概述

本文主要是一个利用filter实现权限拦截的代码实践
我们通过http://localhost:8080/login.jsp 登录页面通过输入admin用户名可以访问登录成功页面
其他均会返回失败页面，并且无法通过http://localhost:8080/sys/success.jsp 直接访问成功页面

实践

web/error.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>错误</h1>
<h3>没有权限或用户名错误</h3>
</body>
</html>

web/index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  $END$
  </body>
</html>

web/login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<form action="/s9/servlet/login" method="post">
    用户名<input type="text" name="username"><hr>
    <input type="submit">
</form>
</body>
</html>

web/sys/login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>主页</h1>
<p><a href="/servlet/logout">注销</p>
</body>
</html>

web/WEB_INF/web.xml

<?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_4_0.xsd"
         version="4.0">

    <servlet>
        <servlet-name>login</servlet-name>
        <servlet-class>com.kuang.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>login</servlet-name>
        <url-pattern>/s9/servlet/login</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>logout</servlet-name>
        <servlet-class>com.kuang.servlet.LogoutServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>logout</servlet-name>
        <url-pattern>/servlet/logout</url-pattern>
    </servlet-mapping>

    <filter>
        <filter-name>sysFliter</filter-name>
        <filter-class>com.kuang.filter.SysFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>sysFliter</filter-name>
        <url-pattern>/sys/*</url-pattern>
    </filter-mapping>
</web-app>

LoginServlet.java

package com.kuang.servlet;

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

/**
 * 功能描述
 *
 * @since 2022-08-26
 */
public class LoginServlet extends HttpServlet {
    @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
        // 获取前端请求参数
        String username = req.getParameter("username");
        if (username.equals("admin")){
            System.out.println("aa");
            req.getSession().setAttribute("USER_SESSION",req.getSession().getId());
//            req.getRequestDispatcher("/sys/success.jsp").forward(req, resp);
            // 跳转采用重定向
            resp.sendRedirect("/sys/success.jsp");
        } else{
            System.out.println("bb");
//            req.getRequestDispatcher("/error.jsp").forward(req, resp);
            resp.sendRedirect("/error.jsp");
        }

    }

    @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
        doGet(req, resp);
    }
}

LogoutServlet.java

package com.kuang.servlet;

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

/**
 * 功能描述
 *
 * @since 2022-08-30
 */
public class LogoutServlet extends HttpServlet {
    @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
        Object userSession = req.getSession().getAttribute("USER_SESSION");
        if (userSession!=null) {
            req.getSession().removeAttribute("USER_SESSION");
            System.out.println("removed");
        }
//        req.getRequestDispatcher("/login.jsp").forward(req, resp);
        resp.sendRedirect("/login.jsp");
    }

    @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
        doGet(req, resp);
    }
}

SysFilter.java

package com.kuang.filter;

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

/**
 * 功能描述
 *
 * @since 2022-08-31
 */
public class SysFilter implements Filter {
    @Override public void init(FilterConfig filterConfig) throws ServletException {
        Filter.super.init(filterConfig);
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
        throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        if(request.getSession().getAttribute("USER_SESSION")==null){
            response.sendRedirect("/error.jsp");
        }
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override public void destroy() {
        Filter.super.destroy();
    }
}

pom

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>JavaWeb-Study</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>09-Filter2</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

</project>

父pom

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>JavaWeb-Study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>01-HelloServlet</module>
        <module>02-ServletContext</module>
        <module>03-Download</module>
        <module>04-VerificationCode</module>
        <module>05-Login</module>
        <module>06-Cookie</module>
        <module>07-Session</module>
        <module>08-Filter</module>
        <module>09-Filter2</module>
    </modules>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>2.3.3</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>jasper</artifactId>
            <version>6.0.53</version>
        </dependency>
    </dependencies>

</project>
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