完整验证码

public class CodeServlet extends HttpServlet {
/**
* 生成验证码图片
* @param request 客户端请求对象
* @param response 响应对象
* @throws ServletException
* @throws IOException
*/
public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {

//设置输出的内容的格式为图象类型，并且为jpeg格式
response.setContentType("image/jpeg");
//设置页面不缓存
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);

// 在内存中创建图象
int width = 60, 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));

//画边框
//g.setColor(new Color());
g.drawRect(0, 0, width - 1, height - 1);

// 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(4位数字)
String code = "";
for (int i = 0; i < 4; i++) {
String rand = String.valueOf(random.nextInt(10));
code += 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);
}

// 将认证码存入SESSION
HttpSession session = request.getSession();
session.setAttribute("extracodeSession", code);

// 图象生效
g.dispose();

// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
}

/**
* 给定范围获得随机颜色
* @param fc 起始值
* @param bc 终止值
* @return 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);
}

/**
* 生成验证码图片
* @param request 客户端请求对象
* @param response 响应对象
* @throws ServletException
* @throws IOException
*/
public void doPost(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
doGet(request, response);
}
}