生成圖片驗證碼

public class SecurityCodeUtil {

    private final static Logger logger                  = LoggerFactory.getLogger(SecurityCodeUtil.class);

    // 驗證碼圖片的寬度。
    private final static int    WIDTH                   = 120;
    // 驗證碼圖片的高度。
    private final static int    HEIGHT                  = 40;

    // 驗證碼干擾線數
    private final static int    INTERFERENCE_LINE_COUNT = 10;

    private final static String RANDOM_CHARS            = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";

    private final static int    MIN_WIDTH               = 20;

    // 得到隨機字符
    public static String randomString(int n) {

        Random random = new Random(System.currentTimeMillis());

        StringBuffer rnd = new StringBuffer();
        String chars = RANDOM_CHARS;

        int len = chars.length() - 1;
        double r;
        for (int i = 0; i < n; i++) {
            r = (random.nextDouble()) * len;
            rnd.append(chars.charAt((int) r));
        }
        return rnd.toString();
    }

    public static byte[] drawImg(String securityCode) {

        // 16k
        ByteArrayOutputStream out = new ByteArrayOutputStream(16 * 1024);

        Graphics2D g = null;
        try {

            int fontWidth = WIDTH / securityCode.length();// 字體的寬度
            if (fontWidth < MIN_WIDTH) {
                throw new RuntimeException("字符過多");
            }

            int fontHeight = HEIGHT - 5;// 字體的高度
            int codeY = HEIGHT - 8;

            // 圖像buffer
            BufferedImage buffImg = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
            // Graphics g = buffImg.getGraphics();
            g = buffImg.createGraphics();
            // 設置背景色
            // g.setColor(getRandColor(200, 250));
            g.setColor(new Color(255, 255, 255));
            g.fillRect(0, 0, WIDTH, HEIGHT);

            g.setColor(new Color(204, 204, 204));
            g.drawRect(0, 0, WIDTH - 1, HEIGHT - 1);

            // 設置字體
            // Font font = getFont(fontHeight);
            Font font = new Font("Fixedsys", Font.PLAIN, fontHeight);
            g.setFont(font);
            Random random = new Random();
            // 設置干擾線
            for (int i = 0; i < INTERFERENCE_LINE_COUNT; i++) {
                int xs = random.nextInt(WIDTH);
                int ys = random.nextInt(HEIGHT);
                int xe = xs + random.nextInt(WIDTH);
                int ye = ys + random.nextInt(HEIGHT);
                g.setColor(randColor(1, 255));
                g.drawLine(xs, ys, xe, ye);
            }

            // 添加噪點
            float yawpRate = 0.01f;// 噪聲率
            int area = (int) (yawpRate * WIDTH * HEIGHT);
            area = 8;
            for (int i = 0; i < area; i++) {
                int x = random.nextInt(WIDTH);
                int y = random.nextInt(HEIGHT);

                buffImg.setRGB(x, y, random.nextInt(255));
            }

            // 得到隨機字符

            char[] codeChars = securityCode.toCharArray();

            for (int i = 0; i < codeChars.length; i++) {
                char strRand = codeChars[i];
                g.setColor(randColor(1, 255));
                // g.drawString(a,x,y);
                // a爲要畫出來的東西，x和y表示要畫的東西最左側字符的基線位於此圖形上下文座標系的 (x, y) 位置處
                g.drawString(String.copyValueOf(new char[] { strRand }), i * fontWidth + 1, codeY);
            }
            ImageIO.write(buffImg, "JPEG", out);

            return out.toByteArray();
        } catch (Exception e) {
            logger.error("驗證碼生產失敗！", e);
        } finally {
            if (g != null) {
                g.dispose();
            }

            try {
                out.close();
            } catch (IOException e) {
                logger.error("", e);
            }
        }
        return new byte[0];
    }

    /**
     * 隨機顏色
     *
     * @param fc 給定範圍獲得隨機顏色
     * @param bc 給定範圍獲得隨機顏色
     * @return
     */
    private static Color randColor(int fc, int bc) {
        Random random = new Random(System.currentTimeMillis());
        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);
    }

}

對應的Response只要設置返回類型就行

response.setContentType("image/jpeg");
                response.addHeader("Accept-Ranges", "bytes");