/**
	 * 圖片驗證碼
	 * @param request
	 * @param response
	 */
	@RequestMapping("/verifyImage")
	public void verifyImage(HttpServletRequest request,HttpServletResponse response) {
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);
		// 表明生成的響應是圖片
		response.setContentType("image/jpeg");

		int width = 80, height = 25;
		BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);

		Graphics g = image.getGraphics();
		Random random = new Random();
		g.setColor(getRandColor(200, 250));
		g.fillRect(1, 1, width - 1, height - 1);
		g.setColor(new Color(102, 102, 102));
		g.drawRect(0, 0, width - 1, height - 1);
		g.setFont(mFont);

		g.setColor(getRandColor(160, 200));

		// 畫隨機線
		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);
		}

		// 從另一方向畫隨機線
		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);
		}

		// 生成隨機數,並將隨機數字轉換為字母
		String sRand = "";
		for (int i = 0; i < 4; i++) {
			int itmp = random.nextInt(26) + 65;
			char ctmp = (char) itmp;
			sRand += String.valueOf(ctmp);
			g.setColor(new Color(20 + random.nextInt(110), 20 + random
					.nextInt(110), 20 + random.nextInt(110)));
			g.drawString(String.valueOf(ctmp), 15 * i + 10, 16);
		}
		g.dispose();
		String key = request.getParameter("key");//從頁面獲取key
		redisHelper.put(key, sRand);//放到redis快取中
		redisHelper.expire(key,5*60*1000);//設定過期時間為5分鐘
		try {
			ImageIO.write(image, "JPEG", response.getOutputStream());
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	public 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);
	}
 

生成驗證碼如下圖