过滤器通过Session实现权限拦截

过滤器的权限拦截

• 编写Session拦截过滤器

package com.filter;

import com.util.Constant;

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

/**
 * @author 125827
 */
public class SysFilter implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {}
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        // ServletRequest    HttpServletRequest
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        if (request.getSession().getAttribute(Constant.USER_SESSION) == null){
            response.sendRedirect( "/Login.jsp" );
        }
        filterChain.doFilter(servletRequest,servletResponse);
    }
    public void destroy() {}
}

• 定义一个Session常量

package com.util;

/**
 * @author 125827
 */
public class Constant {
    public final static String USER_SESSION = "USER_SESSION";
}

• 注册过滤器

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

    <servlet>
        <servlet-name>LoginOutServlet</servlet-name>
        <servlet-class>com.servlet.LoginOutServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginOutServlet</servlet-name>
        <url-pattern>/servlet/login_out</url-pattern>
    </servlet-mapping>

    <!--过滤器-->
    <filter>
        <filter-name>SysFilter</filter-name>
        <filter-class>com.filter.SysFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>SysFilter</filter-name>
        <url-pattern>/sys/*</url-pattern>
    </filter-mapping>

</web-app>

• 准备Servlet

package com.servlet;

import com.util.Constant;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
// 登录
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取前端请求的参数
        String username = req.getParameter("username");
        if(username.equals("admin")){
            //登录成功
            req.getSession().setAttribute(Constant.USER_SESSION,req.getSession().getId());
            resp.sendRedirect("/sys/success.jsp");
        }else{
            resp.sendRedirect("/");
        }
    }
}

package com.servlet;

import com.util.Constant;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
// 登出
public class LoginOutServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Object user_session = req.getSession().getAttribute(Constant.USER_SESSION);
        if(user_session != null ){
            req.getSession().removeAttribute(Constant.USER_SESSION);
            resp.sendRedirect("/Login.jsp");
        }else{
            resp.sendRedirect("/Login.jsp");
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

• 展示页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h1>登录</h1>
    <form action="/servlet/login" method="post">
        <input type="text" name="username">
        <input type="submit">
    </form>
</body>
</html>