Java 登陆验证码

生成验证的类：RandomCode

 

import Java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.util.Random;

import javax.imageio.ImageIO;

import java.io.*;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

@SuppressWarnings("serial")

public class RandomCode extends HttpServlet {

 /**

  * The doGet method of the servlet. <br>

  * 

  * This method is called when a form. has its tag value method equals to

  * get.

  * 

  * @param request

  *            the request send by the client to the server

  * @param response

  *            the response send by the server to the client

  * @throws ServletException

  *             if an error occurred

  * @throws IOException

  *             if an error occurred

  */

 public void doGet(HttpServletRequest request, HttpServletResponse response)

   throws ServletException, IOException {

  this.doPost(request, response);

 }

 /**

  * The doPost method of the servlet. <br>

  * 

  * This method is called when a form. has its tag value method equals to

  * post.

  * 

  * @param request

  *            the request send by the client to the server

  * @param response

  *            the response send by the server to the client

  * @throws ServletException

  *             if an error occurred

  * @throws IOException

  *             if an error occurred

  */

 public void doPost(HttpServletRequest request, HttpServletResponse response)

   throws ServletException, IOException {

  Random random = new Random();

  int width = 60, height = 20;

  // 创建BufferedImage对象，设置图片的长度宽度和色彩。

  BufferedImage image = new BufferedImage(width, height,

    BufferedImage.TYPE_INT_RGB);

  OutputStream os = response.getOutputStream();

  // 取得Graphics对象，用来绘制图片

  Graphics g = image.getGraphics();

  // 绘制图片背景和文字,释放Graphics对象所占用的资源。

  g.setColor(getRandColor(200, 250));

  // 设置内容生成的位置

  g.fillRect(0, 0, width, height);

  // 设置内容的字体和大小

  g.setFont(new Font("Times New Roman", Font.PLAIN, 20));

  // 设置内容的颜色：主要为生成图片背景的线条

  g.setColor(getRandColor(160, 200));

  // 画边框。

  g.setColor(Color.BLACK);

  g.drawRect(0, 0, width - 1, height - 1);

  // 随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。

  g.setColor(Color.BLACK);

  // 图片背景上随机生成155条线条，避免通过图片识别破解验证码

  for (int i = 0; i < 30; i++) {

   int x = random.nextInt(width);

   int y = random.nextInt(height);

   int xl = random.nextInt(12);

   int yl = random.nextInt(12);

   g.drawLine(x, y, x + xl, y + yl);

  }

  // 生成四位的随机数,生成一个数，写一个

  String[] s = { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K",

    "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W",

    "X", "Y", "Z" };

  String content = "";

  for (int i = 0; i < 4; i++) {

   String rand = "";

   if (random.nextBoolean()) {

    rand = String.valueOf(random.nextInt(10));

   } else {

    int index = random.nextInt(25);

    rand = s[index];

   }

   content += rand;

   g.setColor(new Color(20 + random.nextInt(10), 20 + random

     .nextInt(110), 20 + random.nextInt(110)));

   g.drawString(rand, 13 * i + 6, 16);

  }

  // 释放此图形的上下文以及它使用的所有系统资源，类似于关闭流

  g.dispose();

  // 将生成的验证码值(即运算结果的值)放到session中，以便于后台做验证。

  HttpSession session = request.getSession();

  session.setAttribute("result", content);

  // 通过ImageIO对象的write静态方法将图片输出。

  ImageIO.write(image, "JPEG", os);

  os.close();

 }

 /**

  * 生成随机颜色

  * 

  * @param fc

  * @param bc

  * @return

  */

 public Color getRandColor(int fc, int bc) {

  Random random = new Random();

  if (fc > 255)

   fc = 255;

  if (bc > 255)

   bc = 255;

  int r = fc + random.nextInt(bc - fc);

  int g = fc + random.nextInt(bc - fc);

  int b = fc + random.nextInt(bc - fc);

  return new Color(r, g, b);

 }

}

 

 

 

 

web.xml配置：

 

 <!-- 验证码 -->

 <servlet>

    <description>生成验证码的Servlet</description>

    <display-name>RandomCode</display-name>

    <servlet-name>RandomCode</servlet-name>

    <servlet-class>com.gxh.tools.RandomCode</servlet-class>

</servlet>

<servlet-mapping>

    <servlet-name>RandomCode</servlet-name>

    <url-pattern>*.RandomCode</url-pattern>

</servlet-mapping>

 

 

 

 

login.jsp页面：

 

 <script type="text/JavaScript">

   function changeImg()

   {    document.getElementById("validatecodeimg").src=Math.round(Math.random()*10000)+".RandomCode ";

   }

</script>

  <body>

  <div align="center">

  

   <img id="validatecodeimg" alt="看不清？点击刷新" onclick="javascript:changeImg()" src="first.RandomCode " align="top" />  

<a href="javascript:changeImg()">看不清？点击刷新</a>

</div>

  </body>

</html>