验证码的操作与实现

 获取图形验证码

package com.csdn.servlet;

 

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

 

import javax.imageio.ImageIO;

import javax.servlet.ServletException;

import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

 

public class CheckCodeServlet extends HttpServlet {

 

 

     private static final long serialVersionUID = 1L;

     public CheckCodeServlet() {

         super();

     }

 

     public void destroy() {

         super.destroy();

     }

 

 

     private static int WIDTH = 60;

     private static int HEIGHT = 20;

     public void doGet(HttpServletRequest request, HttpServletResponse response)

              throws ServletException, IOException {

 

         response.setContentType("image/jpeg");

         ServletOutputStream out = response.getOutputStream();

         HttpSession session = request.getSession();

        

         /*取消浏览器的缓存*/

         response.setHeader("Pragma", "no-cache");

         response.setHeader("Cache-Controll", "no-cache");

         response.setIntHeader("Expires", 0);

        

        

         /*生成画板*/

         BufferedImage bi = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);/*画板*/

         Graphics g = bi.getGraphics();/*画笔*/

        

         /*画背景*/

         drawBackground(g);

        

         /*随即产生验证码*/

         char[] rands = generateCheckCode();

         drawRands(g,rands);

        

         /*传送到客户端*/

         ByteArrayOutputStream bos = new ByteArrayOutputStream();

         ImageIO.write(bi, "JPEG", bos);

         byte[] buf = bos.toByteArray();/*将内存的图片缓冲区对象bi转换成一个字节数组*/

         out.write(buf);

        

         response.setContentLength(buf.length);

        

         session.setAttribute("checkCode", new String(rands));

        

         out.flush();

         out.close();

     }

    

     /*把生成的数组画到面板上*/

     private void drawRands(Graphics g,char[] rands){

         g.setColor(Color.black);

         g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));

         g.drawString(""+rands[0],1,17);

         g.drawString(""+rands[1],16,18);

         g.drawString(""+rands[2],32,14);

         g.drawString(""+rands[3],46,18);

     }

    

     /*产生四位的验证码*/

     private char[] generateCheckCode(){

         String chars = "0123456789qwertyuiopasdfghjklzxcvbnm";

         char[] rands = new char[4];

         for(int i=0;i<4;i++){

              int random = (int)(Math.random()*36);

              rands[i] = chars.charAt(random);

         }

        

         return rands;

     }

    

     /*画板画背景*/

     private void drawBackground(Graphics g){

         g.setColor(new Color(0xDCDCDC));

         g.fillRect(0, 0, WIDTH, HEIGHT);

        

         for(int i=0;i<120;i++){

              int x = (int)(Math.random()*WIDTH);

              int y = (int)(Math.random()*HEIGHT);

              int red = (int)(Math.random()*255);

              int greed = (int)(Math.random()*255);

              int blue = (int)(Math.random()*255);

              g.setColor(new Color(red,greed,blue));

              g.drawOval(x, y, 1, 0);

         }

     }

 

 

     public void doPost(HttpServletRequest request, HttpServletResponse response)

              throws ServletException, IOException {

        

         doGet(request, response);

     }

 

 

     public void init() throws ServletException {

        

     }

 

}

验证验证码是否正确

package com.csdn.servlet;

 

import java.io.IOException;

import java.io.PrintWriter;

 

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

 

public class LoginFromServlet extends HttpServlet {

 

    private static final longserialVersionUID = 1L;

 

    public LoginFromServlet() {

       super();

    }

 

    public void destroy() {

       super.destroy(); // Just puts "destroy" string in log

       // Put your code here

    }

 

    public void doGet(HttpServletRequest request, HttpServletResponse response)

           throws ServletException, IOException {

 

       response.setContentType("text/html;charset=utf-8");

       HttpSession session = request.getSession();

      

       PrintWriter out = response.getWriter();

       out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");

       out.println("<HTML>");

       out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");

       out.println("  <BODY>");

 

       /*获取session的checkCode属性值*/

       String checkCode1 = (String) session.getAttribute("checkCode");

       /*获取表单中输入的验证码*/

       String checkCode2 = request.getParameter("checkCode").toLowerCase();

       if(checkCode1.equals(checkCode2)){

           out.println("恭喜你登陆成功！");

           out.println("<br/><a href='/demo/loginfrom.html'>返回</a>");

       }else{

           out.println("验证码错误！");

           response.sendRedirect("/demo/loginfrom.html");

       }

       out.println("  </BODY>");

       out.println("</HTML>");

       out.flush();

       out.close();     

    }

 

    public void doPost(HttpServletRequest request, HttpServletResponse response)

           throws ServletException, IOException {

       doGet(request, response);

    }

 

    public void init() throws ServletException {

 

    }

 

}

HTML页面

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

    <title>loginfrom.html</title>

   

    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

    <meta http-equiv="description" content="this is my page">

    <meta http-equiv="content-type" content="text/html; charset=UTF-8">

   

    <!--<link rel="stylesheet" type="text/css"href="./styles.css">-->

 

  </head>

 

  <body>

   <h3>带有验证码的登录页面</h3><br/>

   <form method="post" action="servlet/loginFromServlet">

    用户名：<input type="text" name="userName"/><br/>

    密&nbsp;&nbsp;码：<input type="password" name="password"/><br/>

    验证码：<input type="text" name="checkCode"/>

    &nbsp;&nbsp;<img src="servlet/checkCode" />

    &nbsp;&nbsp;&nbsp;<a href="/authcode/loginfrom.html">看不清楚?换一个</a><br/>  

    <input type="submit" value="提交"/>

    </form>

  </body>

</html>