servlt验证码

package org.cric.util;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import javax.imageio.*;
public class AuthImg extends HttpServlet {
private static final long serialVersionUID = 1L;
//设置字体
private Font mFont = new Font("Arial Black", Font.PLAIN, 16);
public void init() throws ServletException {
super.init();
}
/**
     * 生成随机颜色
     * @param fc 产生颜色值下限(lower limit)
     * @param bc 产生颜色值上限(upper limit)
     * @return 生成的随机颜色对象
     */
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);
}

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);
response.setContentType("image/jpeg");

int width = 100, height = 18;
//生成画布
BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
//获取图形上下文 （生成画笔）
Graphics g = image.getGraphics();
Random random = new Random();
//设置背景色（）
g.setColor(getRandColor(200, 250));
//填充矩形区域 ，作为背景
g.fillRect(1, 1, width - 1, height - 1);
//设置边框颜色
g.setColor(new Color(102, 102, 102));
g.drawRect(0, 0, width - 1, height - 1);
g.setFont(mFont);
//设置随机干扰线条颜色
g.setColor(getRandColor(160, 200));
//产生155条干扰线条
for (int i = 0; i < 155; i++) {
int x = random.nextInt(width - 1);
int y = random.nextInt(height - 1);
int xl = random.nextInt(6) + 1;
int yl = random.nextInt(12) + 1;
g.drawLine(x, y, x + xl, y + yl);
}
for (int i = 0; i < 70; i++) {
int x = random.nextInt(width - 1);
int y = random.nextInt(height - 1);
int xl = random.nextInt(12) + 1;
int yl = random.nextInt(6) + 1;
g.drawLine(x, y, x - xl, y - yl);
}

String sRand = "";
for (int i = 0; i < 6; i++) {
String tmp = getRandomChar();
sRand += tmp;
g.setColor(new Color(20 + random.nextInt(110), 20 + random
.nextInt(110), 20 + random.nextInt(110)));
g.drawString(tmp, 15 * i + 10, 15);
}

HttpSession session = request.getSession(true);
session.setAttribute("rand", sRand);
g.dispose();
ImageIO.write(image, "JPEG", response.getOutputStream());
}

private String getRandomChar() {
//int rand = (int) Math.round(Math.random() * 2);
long itmp = 0;
/*char ctmp = '\u0000';
switch (rand) {
case 1:
itmp = Math.round(Math.random() * 25 + 65);
ctmp = (char) itmp;
return String.valueOf(ctmp);
case 2:
itmp = Math.round(Math.random() * 25 + 97);
ctmp = (char) itmp;
return String.valueOf(ctmp);
default:*/
itmp = Math.round(Math.random() * 9);
return String.valueOf(itmp);
//}
}
}