第四次作业

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

  <script type="text/javascript">
    function reloadCode()
    {
      var time=new Date().getTime();
      document.getElementById("imagecode").src="<%= request.getContextPath()%>/servlet/ImageServlet?d="+time;
    }
  </script>


  <body>
  <form action="<%= request.getContextPath()%>/servlet/UserServlet" method="post" >
   用户名:<input type="text" name="uname"/>
    <br>
   密码:<input type="password"  name="password"/>
    <br>
    验证码:<input  type="text" name="checkCode"/>
    <a href="javascript:reloadCode();">
      <img alt="验证码" id="imagecode" src="<%= request.getContextPath()%>/servlet/ImageServlet"/>
      不太清楚</a><br>
    <input type="submit" value="登录">
  </form>
  </body>


</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h2 style="color: cadetblue">登录成功！！！！！！！！</h2>
</body>
</html>

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(urlPatterns="/servlet/UserServlet")
public class UserServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("do Post");
        String uname = request.getParameter("uname");
        String password = request.getParameter("password");
        System.out.println(uname+"----"+password);

   
        String piccode=(String) request.getSession().getAttribute("piccode");
        String checkCode=request.getParameter("checkCode");  
        checkCode=checkCode.toUpperCase();  
        response.setContentType("text/html;charset=gbk");
        PrintWriter out=response.getWriter();
        if(checkCode.equals(piccode) && "lty".equals(uname) && "123456".equals(password))
        {
          
            String contextPath = request.getContextPath();
            response.sendRedirect(contextPath+"/ok.jsp");
        }
        else
        {
            request.getRequestDispatcher("/index.jsp").forward(request, response);
        }
        out.flush();
        out.close();

    }

}

package servlet;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(urlPatterns="/servlet/ImageServlet")
public class ImageServlet  extends HttpServlet{
    public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException{
        //这个方法实现验证码的生成
        BufferedImage bi=new BufferedImage(68, 22,BufferedImage.TYPE_INT_RGB);//创建图像缓冲区
        Graphics g=bi.getGraphics(); //通过缓冲区创建一个画布
        Color c=new Color(253, 161,255); //创建颜色
        /*根据背景画了一个矩形框
         */
        g.setColor(c);//为画布创建背景颜色
        g.fillRect(0, 0, 68,22); //fillRect:填充指定的矩形

        char[] ch="ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toCharArray();//转化为字符型的数组
        Random r=new Random();
        int len=ch.length;
        int index; //index用于存放随机数字
        StringBuffer sb=new StringBuffer();
        for(int i=0;i<4；i++)

        {
            index=r.nextInt(len);
            g.setColor(new Color(r.nextInt(88),r.nextInt(188),r.nextInt(255))); 
            g.drawString(ch[index]+"",(i*15)+3, 18);
            sb.append(ch[index]);
        }
        request.getSession().setAttribute("piccode",sb.toString()); 
        ImageIO.write(bi, "JPG", response.getOutputStream());
    }}

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原文地址：https://www.cnblogs.com/zhangjun19991118/p/14584942.html