Java Session验证码案例代码实例解析

案例

用户输入用户名，密码以及验证码。

如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误

如果验证码输入有误，跳转登录页面，提示：验证码错误

如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您思路

在生成验证码的时候将它的值存入到session中，在比对的时候再取出来进行对比

代码index.jsp

<%--
 Created by IntelliJ IDEA.
 User: tanglei
 Date: 2020/6/26
 Time: 下午12:48
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType=\"text/html;charset=UTF-8\" language=\"java\" %>
<html>
<head>
  <title>login</title>


  <script>
    window.onload = function(){
      document.getElementById(\"img\").onclick = function(){
        this.src=\"/login_time_war_exploded/checkCode?time=\"+new Date().getTime();
      }
    }


  </script>
  <style>
    div{
      color: red;
    }

  </style>
</head>
<body>

<form action=\"/login_time_war_exploded/login\" 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=\"/login_time_war_exploded/checkCode\"></td>
    </tr>
    <tr>
      <td colspan=\"2\"><input type=\"submit\" value=\"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>

success.jsp

<%--
 Created by IntelliJ IDEA.
 User: tanglei
 Date: 2020/6/26
 Time: 下午6:27
 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>
<h1><%=request.getSession().getAttribute(\"user\")%>,欢迎您</h1>
</body>
</html>

验证码checkCode.java

package cn.guizimo.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(\"/checkCode\")
public class CheckCode extends HttpServlet {
  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    int width = 100;
    int height = 50;
    //创建图片对象
    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);

    //美化
    Graphics g = image.getGraphics();
    //背景
    g.setColor(Color.PINK);
    g.fillRect(0, 0, width, height);
    //边框
    g.setColor(Color.BLUE);
    g.drawRect(0, 0, width - 1, height - 1);

    String str = \"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789\";
    Random ran = new Random();
    StringBuilder sb = new StringBuilder();
    for (int i = 1; i <= 4; i++) {
      int index = ran.nextInt(str.length());
      char ch = str.charAt(index);
      sb.append(ch);
      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);

    //干扰线
    g.setColor(Color.GREEN);
    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,y1,x2,y2);
    }


  //输出图片到浏览器
    ImageIO.write(image, \"jpg\", resp.getOutputStream());

  }

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

package cn.guizimo.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(\"/login\")
public class Login extends HttpServlet {
  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    //1.设置request编码
    req.setCharacterEncoding(\"utf-8\");
    //2.获取参数
    String username = req.getParameter(\"username\");
    String password = req.getParameter(\"password\");
    String checkCode = req.getParameter(\"checkCode\");
    //3.先获取生成的验证码
    HttpSession session = req.getSession();
    String checkCode_session = (String) session.getAttribute(\"checkCode_session\");
    //删除session中存储的验证码
    //session.removeAttribute(\"checkCode_session\");
    //3.先判断验证码是否正确
    if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(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.jsp
        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 doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    this.doPost(req, resp);
  }
}

测试登录界面