JSP生成验证码
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);
}
%>
<html>
<body>
<%
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();
%>
</body>
</html>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。