在浏览网页时，我们会经常看到验证码，尤其是登录和注册的时候，今天就为大家介绍一下如何使用JSP生成验证码图片，原理其实是很简单的，直接上代码：

<%@ page contentType="image/jpeg;charset=utf-8" pageEncoding="GBK" %><%@    page import="java.util.*,java.awt.*,java.awt.image.*,javax.imageio.*"         import="java.io.OutputStream" %><%!   Color getRandColor(int fc,int bc)   {      Random rd = new Random();      if (fc > 255) fc = 255;      if (bc > 255) bc = 255;      int red = fc + rd.nextInt(bc - fc);      int green = fc + rd.nextInt(bc - fc);      int blue = fc + rd.nextInt(bc - fc);      return new Color(red, green, blue);   }%>   <%   Random r = new Random();   response.addHeader("Pragma", "No-cache");   response.addHeader("Cache-Control", "no-cache");   response.addDateHeader("expires", 0);   int width = 80;   int height = 32;   BufferedImage pic = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);   Graphics gc = pic.getGraphics();   gc.setColor(getRandColor(200, 250));   gc.fillRect(0, 0, width, height);   String[] rNum = {
    "1", "2", "3", "4", "5", "6", "7", "8", "9",         "A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "L", "M", "N",         "P", "Q", "R", "S", "T", "W", "X", "Y", "Z"};   int[] style = {Font.PLAIN, Font.BOLD, Font.ITALIC, Font.PLAIN + Font.BOLD, Font.BOLD + Font.ITALIC,         Font.PLAIN + Font.ITALIC, Font.PLAIN + Font.BOLD + Font.ITALIC};   gc.setColor(getRandColor(60,150));   String rt = "";   for(int i = 0; i < 4; i++)   {      String temp = rNum[r.nextInt(rNum.length)];      rt = rt + temp;      gc.setFont(new Font("Times New Roman", style[r.nextInt(7)], 21));      gc.drawString(temp, 15 + 13 * i + r.nextInt(2), 23);   }   gc.dispose();   OutputStream os = response.getOutputStream();   ImageIO.write(pic, "JPEG", os);   os.flush();   os.close();   os = null;   response.flushBuffer();   out.clear();   out = pageContext.pushBody();%>   

运行程序，通过浏览器访问，我们会看到浏览器上显示

大家可以自己尝试在绘图的时候增加一些删除线之类的，提高验证码识别难度。