验证码

//生成BufferedImage图片对象
private BufferedImage getImage(HttpSession session) {
// 在内存中创建图象
int width = 85, height = 20;
BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
// 获取图形上下文
Graphics g = image.getGraphics();
// 生成随机类
Random random = new Random();
// 设定背景色
g.setColor(getRandColor(200, 250));
g.fillRect(0, 0, width, height);
// 设定字体
g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
g.setColor(getRandColor(160, 200));
for (int i = 0; i < 155; i++) {
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(12);
int yl = random.nextInt(12);
g.drawLine(x, y, x + xl, y + yl);
}
// 取随机产生的认证码(6位数字)
String sRand = "";
for (int i = 0; i < 2; i++) {
String rand = String.valueOf(random.nextInt(10));
sRand += rand;
// 将认证码显示到图象中
g.setColor(new Color(20 + random.nextInt(110), 20 + random
.nextInt(110), 20 + random.nextInt(110)));
// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
g.drawString(rand, 13 * i + 6, 16);
}
// 赋值验证码(关键点)
session.setAttribute("rand", sRand);

// 图象生效
g.dispose();

return image;
}

/*
* 给定范围获得随机颜色
*/
private 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);
}

@RequestMapping("/getRand")
public void getRand(HttpServletResponse response,HttpSession session) {
response.setHeader(" Pragma ", " No-cache ");
response.setHeader(" Cache-Control ", " no-cache ");
response.setDateHeader(" Expires ", 0);
OutputStream os=null;
try {
//返回字节流
os = response.getOutputStream();
//写图像到response的输出流中
ImageIO.write(getImage(session), "jpg", os);

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (os != null) {
try {
os.flush();
os.close();

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
}

try {
//立即发送缓冲区中的输出
response.flushBuffer();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}