java验证码增加用户读取验证码的难度和干扰效果

package com.sec.control;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

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 VerifyCodeServlet extends HttpServlet {

private static final long serialVersionUID = 1668221467610842602L;

// 验证码图片的宽度
private int width = 60;
// 验证码图片的高度
private int height = 20;
// 验证码字符个数
private int codeCount = 4;
private int x = 0;
// 字体高度
private int fontHeight;
private int codeY;
char[] codeSequence = { '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', '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', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

public void initxuan() throws ServletException {
// 从web.xml中获取初始信息
// 宽度
String strWidth = "80";
// 高度
String strHeight = "30";
// 字符个数
String strCodeCount = "4";
// 将配置信息转换成数值
try {
if (strWidth != null && strWidth.length() != 0) {
width = Integer.parseInt(strWidth);
}
if (strHeight != null && strHeight.length() != 0) {
height = Integer.parseInt(strHeight);
}
if (strCodeCount != null && strCodeCount.length() != 0) {
codeCount = Integer.parseInt(strCodeCount);
}
} catch (NumberFormatException e) {

}
x = width / (codeCount + 1);
fontHeight = height - 2;
codeY = height - 4;
}

// @RequestMapping(value="xuan/verifyCode",method=RequestMethod.GET)//get请求
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
initxuan();
// 定义图像buffer
BufferedImage buffImg = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
Graphics2D g = buffImg.createGraphics();
// 创建一个随机数生成类
Random random = new Random();

// 设置随机背景色
// Color color = new Color(random.nextInt(255), random.nextInt(255),
// random.nextInt(255));
// 填充深色背景
// g.setColor(color.darker());
// 填充较明亮的背景
// g.setColor(color.brighter());

// 将图像填充为粉红色
//g.setColor(Color.PINK);
//白色
g.setColor(Color.white);
// 矩形
g.fillRect(0, 0, width, height);
// 创建字体，字体的大小应该根据图片的高度来定。
// Font font = new Font("Fixedsys",Font.PLAIN,fontHeight);
Font font = new Font("Fixedsys", Font.BOLD, fontHeight);
// 设置字体
g.setFont(font);
// 画边框
g.setColor(Color.GRAY);
g.drawRect(0, 0, width - 1, height - 1);
// 随机产生40个点和40条干扰线，使图像的认证码不易被其它程序探测到
g.setColor(Color.LIGHT_GRAY);
for (int i = 0; i < 40; i++) {
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(50);
int yl = random.nextInt(50);
// 点
g.drawOval(x, y, 1, 1);
// 线
g.drawLine(x, y, x + xl, y + yl);
}

// randomCode用于保存随机产生的验证码，以便用户登录验证
StringBuffer randomCode = new StringBuffer();
int red = 0, green = 0, blue = 0;
// 随机产生codeCount数字的验证码
for (int i = 0; i < codeCount; i++) {
// 随机产生的验证码数字
// String strRand =
// String.valueOf(codeSequence[random.nextInt(codeSequence.length-1)]);
String strRand = String.valueOf(codeSequence[random.nextInt(62)]);

// 文字变形设置
AffineTransform fontAT = new AffineTransform();
int rotate = random.nextInt(25);
fontAT.rotate(random.nextBoolean() ? Math.toRadians(rotate) : -Math
.toRadians(rotate / 2));
Font fx = new Font(new String[] { "Times New Roman", "Verdana",
"arial" }[random.nextInt(2)], random.nextInt(5),
20 + random.nextInt(16)).deriveFont(fontAT);
g.setFont(fx);

// 产生随机的颜色分量来构造颜色值，这样输出的每一位数字的颜色值都不同
red = random.nextInt(255);
green = random.nextInt(255);
blue = random.nextInt(255);
// 将随机产生的颜色将验证码绘制到图像中
g.setColor(new Color(red, green, blue));
g.drawString(strRand, (i + 1) * x - 8, codeY);
// 将产生的四个随机数组合在一起
randomCode.append(strRand);
}
// 将四位数字的验证码保存到Session中
HttpSession session = req.getSession();
session.setAttribute("validateCode", randomCode.toString());
// 禁止图像缓存
resp.setHeader("Pragma", "no-cache");
resp.setHeader("Cache-Control", "no-cache");
resp.setDateHeader("Expires", 0);
resp.setContentType("imag/jpeg");
// 将图像输出到Servlet输出流中
ServletOutputStream sos = resp.getOutputStream();
ImageIO.write(buffImg, "jpeg", sos);
sos.close();
}
}