filter_登录验证案例

需求：

访问day_07案例的资源验证其是否登录
如果登录了则直接放行
如果没有登录则跳转到登录页面提示“您尚未登录请先登录”

登录代码

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录页面</title>
<script>
    window.onload=function () {
        document.getElementById("img").onclick=function () {
            this.src="/CheckCodeServlet?time="+new Date().getTime();
        }
    }
</script>
    <style>
        div{
            color:red;
        }
    </style>

</head>
<body>
    <form action="/loginServlet" method="post">
        <table>
            <tr>
                <td>用户名</td>
                <td><input type="text" name="username"></td>
            </tr>
            <tr>
                <td>密码</td>
                <td><input type="password" name="password"></td>
            </tr>
            <tr>
                <td>验证码</td>
                <td><input type="text" name="checkCode"></td>
            </tr>
            <tr>
                <td colspan="2"><img id="img" src="/CheckCodeServlet"></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" name="登录"></td>
            </tr>

        </table>
    </form>

    <div><%=request.getAttribute("cc_error")==null ? "" :request.getAttribute("cc_error")%></div>
    <div><%=request.getAttribute("login_error")==null ? "" :request.getAttribute("login_error")%></div>

</body>
</html>

欢迎页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>欢迎页面</title>
</head>
<body>
    <h1><%=request.getSession().getAttribute("user")%>,欢迎您</h1>
</body>
</html>

验证码生成

package com.bai.servlet;

import javax.imageio.ImageIO;
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.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/CheckCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        int width = 100;
        int height = 50;

        //1.创建一对象 在内存中图片（验证码图片对象）
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //2.美化图片
        //2.1填充背景色
        Graphics g = image.getGraphics();//画笔对象
        g.setColor(Color.PINK);
        g.fillRect(0,0,width,height);

        //2.2画边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width-1 ,height-1);

        String str="ABCDEFGHIJLMNOPQRTUVWXYZabcdefghigklmnopqstuvwxyz0123456789";

        //生成随机角标
        Random ran = new Random();
        StringBuilder sb = new StringBuilder();
        for (int i=1;i<=4;i++){
            int index=ran.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);//随机字符
            sb.append(ch);
            //2.3写验证码
            g.drawString(ch+"",width/5*i,height/2);
        }
        String checkCode_session = sb.toString();
        //将验证码存入session
        req.getSession().setAttribute("checkCode_session",checkCode_session);

        //2.4画干扰线
        g.setColor(Color.GREEN);
        //随机生成坐标点
        for (int i = 0; i < 10; i++) {
            int x1=ran.nextInt(width);
            int x2=ran.nextInt(width);

            int y1=ran.nextInt(height);
            int y2=ran.nextInt(height);
            g.drawLine(x1,x2,y1,y2);
        }

        //3.将图片输出到页面展示
        ImageIO.write(image,"jpg",resp.getOutputStream());



    }

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

LoginServlet类

package com.bai.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;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置request编码
        req.setCharacterEncoding("utf-8");
        //获取参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String checkCode = req.getParameter("checkCode");
        //获取生成的验证码
        HttpSession session = req.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");
        //判断验证码是否正确
        if (checkCode_session.equals(checkCode)) {
            //忽略大小写比较
            //验证码正确
            //判断用户名和密码是否一致
            if ("zhangsan".equals(username) && "123".equals(password)) {//需要调用UserDao查询数据库
                //登录成功
                //存储信息 用户信息
                session.setAttribute("user", username);
                //重定向到success
                resp.sendRedirect(req.getContextPath() + "/success.jsp");
            } else {
                //登录失败
                //存储提示信息到request
                req.setAttribute("login_error", "用户名或密码错误");
                //转发到登录页面
                req.getRequestDispatcher("/login.jsp").forward(req, resp);
            }

        } else {
            //验证码不一致
            //存储提示信息到request
            req.setAttribute("cc_error","验证码错误");
            //转发到登录页面
            req.getRequestDispatcher("/login.jsp").forward(req,resp);
        }
    }


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

登录页面

拦截器代码

package com.bai.filter;

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

/**
 * 登录验证的过滤器
 */
@WebFilter("/*")
public class LoginFilter implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        //强转转换
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        //获取资源请求路径
        String uri = request.getRequestURI();
        //判断是否包含登录相关资源路径
        if (uri.contains("/login.jsp") || uri.contains("/loginServlet") ||
                uri.contains("/css/") || uri.contains("/js/") || uri.contains("/fonts/")
                || uri.contains("/CheckCodeServlet")) {
            //包含 用户就想登录 放行
            filterChain.doFilter(servletRequest, servletResponse);
        } else {
            //不包含 需要验证用户是否登录
            //获取session中获取user
            Object user = request.getSession().getAttribute("user");
            if (user != null) {
                //登录了 放行
                filterChain.doFilter(servletRequest, servletResponse);
            } else {
                //没有登录 跳转登录页面
                request.setAttribute("login_msg", "您尚未登录 请登录");
                request.getRequestDispatcher("/login.jsp").forward(request, servletResponse);
            }
        }
    }

    public void destroy() {

    }
}