protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {

		Random random = new Random();
		int colorRandoMin = 200;
		int colorRandoMax = 255;

		// int randomNum = random.nextInt(randoMax) % (randoMax - randoMin + 1)
		// + randoMin;

		// 生成验证码
		BufferedImage bufferedImage = new BufferedImage(68, 23,
				BufferedImage.TYPE_INT_RGB);

		// 绘图上上下文对象
		Graphics graphics = bufferedImage.createGraphics();

		// 画个背景
		// 三元色数值随机产生
		// 设置颜色
		graphics.setColor(new Color(random.nextInt(colorRandoMax
				- colorRandoMin + 1)
				+ colorRandoMin, random.nextInt(colorRandoMax - colorRandoMin
				+ 1)
				+ colorRandoMin, random.nextInt(colorRandoMax - colorRandoMin
				+ 1)
				+ colorRandoMin));
		// 填充矩形
		graphics.fillRect(0, 0, 68, 23);

		// 绘制文字
		char[] valChar = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
				.toCharArray();

		// 索引
		int index = 0;
		int len = valChar.length;

		// 用来拼接字符存储进session
		StringBuilder sb = new StringBuilder();

		// 重设文字颜色范围
		colorRandoMin = 1;
		colorRandoMax = 130;

		// 生成4个字符
		for (int i = 0; i < 4; i++) {

			// 生成索引
			index = random.nextInt(len);

			graphics.setFont(new Font("Arial", Font.BOLD, 16));

			// 设置文字颜色
			graphics.setColor(new Color(random.nextInt(colorRandoMax
					- colorRandoMin + 1)
					+ colorRandoMin, random.nextInt(colorRandoMax
					- colorRandoMin + 1)
					+ colorRandoMin, random.nextInt(colorRandoMax
					- colorRandoMin + 1)
					+ colorRandoMin));
			// 绘制文字
			graphics.drawString(valChar[index] + "", i * 15 + 5, 18);

			sb.append(valChar[index]);
		}

		// 存储在session中
		request.getSession().setAttribute("validateCode", sb.toString());
		sb = null;

		// 输入验证码图
		OutputStream out = response.getOutputStream();
		ImageIO.write(bufferedImage, "jpg", out);

		// 刷新并关闭输出流
		out.flush();
		out.close();

	}