LogoutServlet:

package com.kakafa.servlet;

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

public class LogoutServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Object user_session = req.getSession().getAttribute("USER_SESSION");
        if (user_session.equals(null)){
            req.getSession().removeAttribute("USER_SESSION");
            resp.sendRedirect("/j/index.jsp");
        }else{
            resp.sendRedirect("/j/index.jsp");
        }
    }

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

LoginServlet:

package com.kakafa.servlet;

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

public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(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")){
            req.getSession().setAttribute("USER_SESSION",req.getSession().getId());
            resp.sendRedirect("/j/sys/success.jsp");
        }else{
            resp.sendRedirect("/j/error.jsp");
        }
    }

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

登陆页面index.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


登陆页面

    
    

登录成功页面success.jsp：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


主页:登录成功！

注销

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


登陆失败

返回到初始页面

package com.kakafa.filter;

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

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

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {


        //假如session是空的，说明没有登录，则直接转到error页面
        //ServletRequest HttpServletRequest 是父子关系，为了获取到session强制转换一下
        HttpServletRequest request1=(HttpServletRequest) servletRequest;
        HttpServletResponse response1=(HttpServletResponse) servletResponse;

        Object user_session = request1.getSession().getAttribute("USER_SESSION");
        if (user_session==null){
            response1.sendRedirect("/j/error.jsp");
        }else{
            filterChain.doFilter(request1,response1);
        }


    }

    @Override
    public void destroy() {

    }
}

 
        login
        com.kakafa.servlet.LoginServlet
    
    
        login
        /servlet/login
    

    
        logout
        com.kakafa.servlet.LogoutServlet
    
    
        logout
        /servlet/logout
    

    
        sysFilter
        com.kakafa.filter.SysFilter
    
    
        sysFilter
        /sys/*