验证码的用到技术有其中两个基本要点,一是随机数的生成,二是中文,数字，字母的生成，其他的还有加密技术，这里不讲。
先讲随机数的生成:
/** * 验证码生成技术一:随机数生成 * * @author WuChaoWen * @since Jun 1, 2012 */ public class RandomDemo { public static void main(String[] args) { /** * Random类包含两个构造方法，下面依次进行介绍： * a、public Random() 该构造方法使用一个和当前系统时间对应的相对时间有关的数字作为种子数，然后使用这个种子数构造Random对象。 b、public Random(long seed) 该构造方法可以通过制定一个种子数进行创建。种子数只是随机算法的起源数字，和生成的随机数字的区间无关。 */ //以当前时间加1为随机数生成器的种子 Random random = new Random(new java.util.Date().getTime()+1); System.out.println(random.nextInt()); } }
生成中文，数字，字母的方法:
public class RandomHanzi { public static void main(String[] args) { // 输出随机的验证文字 Random random = new Random(); String ctmp = ""; int itmp = 0; for (int i = 0; i < 4; i++) { //random = new Random(new java.util.Date().getTime() + i); switch (random.nextInt(4)) { case 1: itmp = random.nextInt(26) + 65; // 生成A~Z的字母 ctmp = String.valueOf((char) itmp); System.out.println("生成字母:" + ctmp); break; case 2: // 生成汉字 String[] rBase = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" }; // 生成第1位的区码 int r1 = random.nextInt(3) + 11; //生成11到14之间的随机数 String str_r1 = rBase[r1]; // 生成第2位的区码 int r2; if (r1 == 13) { r2 = random.nextInt(7); //生成0到7之间的随机数 } else { r2 = random.nextInt(16); //生成0到16之间的随机数 } String str_r2 = rBase[r2]; // 生成第1位的位码 int r3 = random.nextInt(6) + 10; //生成10到16之间的随机数 String str_r3 = rBase[r3]; // 生成第2位的位码 int r4; if (r3 == 10) { r4 = random.nextInt(15) + 1; //生成1到16之间的随机数 } else if (r3 == 15) { r4 = random.nextInt(15); //生成0到15之间的随机数 } else { r4 = random.nextInt(16); //生成0到16之间的随机数 } String str_r4 = rBase[r4]; System.out.println(str_r1 + str_r2 + str_r3 + str_r4); // 将生成机内码转换为汉字 byte[] bytes = new byte[2]; //将生成的区码保存到字节数组的第1个元素中 String str_r12 = str_r1 + str_r2; int tempLow = Integer.parseInt(str_r12, 16); bytes[0] = (byte) tempLow; //将生成的位码保存到字节数组的第2个元素中 String str_r34 = str_r3 + str_r4; int tempHigh = Integer.parseInt(str_r34, 16); bytes[1] = (byte) tempHigh; ctmp = new String(bytes); //根据字节数组生成汉字 System.out.println("生成汉字:" + ctmp); break; default: itmp = random.nextInt(10) + 48; // 生成0~9的数字 ctmp = String.valueOf((char) itmp); System.out.println("生成数字:" + ctmp); break; } } } }
下面做一个小例子:
1.新建一个web项目，生成index.jsp，代码如下:
<%@ page language="java" contentType="text/html; charset=gb2312" import="java.util.*" %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>英文、数字和中文混合的彩色验证码</title> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"> <script language="javascript"> function checkform(myform){ for(i=0;i<myform.length;i++){ if(myform.elements[i].value==""){ alert(myform.elements[i].title+"不能为空！"); myform.elements[i].focus(); return false; } } } function myReload(){ //document.getElementById("createCheckCode").src="PictureCheckCode"; document.getElementById("createCheckCode").src=document.getElementById("createCheckCode").src+"?nocache="+new Date().getTime(); } </script> </head> <body> <form name="form1" method="post" action="deal.jsp" onSubmit="return checkform(form1)"> 验证码：<input name="checkCode" type="text" id="checkCode" title="验证码区分大小写" size="8" maxlength="4"> <br/> <img src="PictureCheckCode" id="createCheckCode"><a href="#" onClick="myReload()"> 看不清?换一个</a> </form> </body> </html>
2.输入验证码后提交处理的页面:deal.jsp
<%@ page contentType="text/html; charset=utf-8" language="java" errorPage="" %> <% request.setCharacterEncoding("GBK"); String checkCode = request.getParameter("checkCode"); if ("".equals(checkCode) || checkCode == null) { out.println("<script>alert('请输入验证码！');window.location.href='index.jsp';</script>"); } else { if (!checkCode.equals(session.getAttribute("randCheckCode"))) { out.println("<script>alert('您输入的验证码不正确！');history.back(-1);</script>"); } } if("".equals(request.getParameter("username")) || "".equals(request.getParameter("pwd"))){ out.println("<script>alert('请输入用户名或密码！');window.location.href='index.jsp';</script>"); }else{ if(!("mr".equals(request.getParameter("username")) && "mrsoft".equals(request.getParameter("pwd")))){ out.println("<script>alert('您输入的用户名或密码不正确！');window.location.href='index.jsp';</script>"); } } %>
3.生成验证码的servlet
/** * @(#)PictureCheckCode.java * * Copyright XXX.All rights reserved. * This software is the XXX system. * * @Version: XXX * @JDK: jdk 1.6.0.XXX * @Module: VerificationCode01 */ /*- History ********************************************** * ID DATE PERSON REASON * 1 Jun 1, 2012 WuChaoWen Created ********************************************** */ package com.chaowen.code; import java.awt.BasicStroke; import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.geom.AffineTransform; import java.awt.geom.Line2D; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random; import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; /** * Class description goes here. * * @author WuChaoWen * @since Jun 1, 2012 */ public class PictureCheckCode extends HttpServlet { public PictureCheckCode() { super(); } public void destroy() { super.destroy(); } public void init() throws ServletException { super.init(); } // 获取随机颜色 public Color getRandColor(int s, int e) { Random random = new Random(); if (s > 255) s = 255; if (e > 255) e = 255; int r = s + random.nextInt(e - s); //随机生成RGB颜色中的r值 int g = s + random.nextInt(e - s); //随机生成RGB颜色中的g值 int b = s + random.nextInt(e - s); //随机生成RGB颜色中的b值 return new Color(r, g, b); } public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setHeader("Pragma", "No-cache"); response.setHeader("Cache-Control", "No-cache"); response.setDateHeader("Expires", 0); // 指定生成的响应是图片 response.setContentType("image/jpeg"); int width = 86; int height = 22; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics(); Graphics2D g2d = (Graphics2D) g; Random random = new Random(); Font mFont = new Font("黑体", Font.BOLD, 17); g.setColor(getRandColor(200, 250)); g.fillRect(0, 0, width, height); g.setFont(mFont); g.setColor(getRandColor(180, 200)); // 画随机的线条 for (int i = 0; i < 100; i++) { int x = random.nextInt(width - 1); int y = random.nextInt(height - 1); int x1 = random.nextInt(6) + 1; int y1 = random.nextInt(12) + 1; BasicStroke bs = new BasicStroke(2f, BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL); Line2D line = new Line2D.Double(x, y, x + x1, y + y1); g2d.setStroke(bs); g2d.draw(line); } String sRand = ""; // 输出随机的验证文字 String ctmp = ""; int itmp = 0; for (int i = 0; i < 4; i++) { //random = new Random(new java.util.Date().getTime() + i); switch (random.nextInt(4)) { case 1: itmp = random.nextInt(26) + 65; // 生成A~Z的字母 ctmp = String.valueOf((char) itmp); break; case 2: // 生成汉字 String[] rBase = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" }; // 生成第1位的区码 int r1 = random.nextInt(3) + 11; //生成11到14之间的随机数 String str_r1 = rBase[r1]; // 生成第2位的区码 int r2; if (r1 == 13) { r2 = random.nextInt(7); //生成0到7之间的随机数 } else { r2 = random.nextInt(16); //生成0到16之间的随机数 } String str_r2 = rBase[r2]; // 生成第1位的位码 int r3 = random.nextInt(6) + 10; //生成10到16之间的随机数 String str_r3 = rBase[r3]; // 生成第2位的位码 int r4; if (r3 == 10) { r4 = random.nextInt(15) + 1; //生成1到16之间的随机数 } else if (r3 == 15) { r4 = random.nextInt(15); //生成0到15之间的随机数 } else { r4 = random.nextInt(16); //生成0到16之间的随机数 } String str_r4 = rBase[r4]; System.out.println(str_r1 + str_r2 + str_r3 + str_r4); // 将生成机内码转换为汉字 byte[] bytes = new byte[2]; //将生成的区码保存到字节数组的第1个元素中 String str_r12 = str_r1 + str_r2; int tempLow = Integer.parseInt(str_r12, 16); bytes[0] = (byte) tempLow; //将生成的位码保存到字节数组的第2个元素中 String str_r34 = str_r3 + str_r4; int tempHigh = Integer.parseInt(str_r34, 16); bytes[1] = (byte) tempHigh; ctmp = new String(bytes); //根据字节数组生成汉字 // System.out.println("生成汉字:" + ctmp); break; default: itmp = random.nextInt(10) + 48; // 生成0~9的数字 ctmp = String.valueOf((char) itmp); break; } sRand += ctmp; Color color = new Color(20 + random.nextInt(110), 20 + random .nextInt(110), 20 + random.nextInt(110)); g.setColor(color); /** **随机缩放文字并将文字旋转指定角度* */ // 将文字旋转指定角度 Graphics2D g2d_word = (Graphics2D) g; AffineTransform trans = new AffineTransform(); trans.rotate(random.nextInt(45) * 3.14 / 180, 15 * i + 8, 7); // 缩放文字 float scaleSize = random.nextFloat() +0.8f; if (scaleSize > 1f) scaleSize = 1f; trans.scale(scaleSize, scaleSize); g2d_word.setTransform(trans); /** ********************* */ g.drawString(ctmp, 15 * i + 18, 14); } // 将生成的验证码保存到Session中 HttpSession session = request.getSession(true); session.setAttribute("randCheckCode", sRand); g.dispose(); ImageIO.write(image, "JPEG", response.getOutputStream()); } }