Java生成随机验证码

    @RequestMapping("captcha")
    public void writeCaptcha(HttpServletRequest request, HttpServletResponse response) throws IOException {
        final HttpSession session = request.getSession(true);

        CaptchaImageGenerator captchaImageGenerator = new CaptchaImageGenerator();
        final BufferedImage image = captchaImageGenerator.generate();
        //save to session
        WebUtils.setCaptchaKey(session, captchaImageGenerator.code());

        response.setHeader("Cache-Control", "no-store");
        response.setHeader("Pragma", "no-cache");
        response.setDateHeader("Expires", 0);
        response.setContentType("image/png");

        final ServletOutputStream output = response.getOutputStream();
        ImageIO.write(image, "png", output);
        output.flush();
    }

CaptchaImageGenerator.java

public class CaptchaImageGenerator {


    private Random random = new Random();
    //随机产生的字符串
    private String randString = "012EFGHI789ABCDJ56KLMNPQR34STUVWXYZ";

    //图片宽
    private int width = 80;
    //图片高
    private int height = 26;
    //干扰线数量
    private int lineSize = 10;
    //随机产生字符数量
    private int charSize = 4;

    //图片上的文字
    private String code = "";

    //字体
    private Font font = new Font("Times New Roman", Font.PLAIN, 18);

    public CaptchaImageGenerator() {
    }

    //设置干扰线数量, 默认为10
    public CaptchaImageGenerator lineSize(int lineSize) {
        if (lineSize < 0) {
            throw new IllegalArgumentException("lineSize < 0");
        }
        this.lineSize = lineSize;
        return this;
    }

    //设置产生的字符数量 , 默认为4
    public CaptchaImageGenerator charSize(int charSize) {
        if (charSize < 0) {
            throw new IllegalArgumentException("charSize < 0");
        }
        this.charSize = charSize;
        return this;
    }


    //设置图片的宽度
    public CaptchaImageGenerator width(int width) {
        if (width < 0) {
            throw new IllegalArgumentException("width < 0");
        }
        this.width = width;
        return this;
    }

    //设置图片的高度
    public CaptchaImageGenerator height(int height) {
        if (height < 0) {
            throw new IllegalArgumentException("height < 0");
        }
        this.height = height;
        return this;
    }


    //获取图片中生成的字符内容
    public String code() {
        return this.code;
    }


    /**
     * 生成图片
     *
     * @return BufferedImage instance
     */
    public BufferedImage generate() {

        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
        Graphics g = image.getGraphics();
        g.fillRect(0, 0, width, height);

        g.setFont(font);
        g.setColor(getRandColor(110, 133));
        //绘制干扰线
        for (int i = 0; i <= lineSize; i++) {
            drewLine(g);
        }

        for (int i = 1; i <= charSize; i++) {
            drewString(g, i);
        }

        g.dispose();
        return image;
    }


    /*
    * 获得颜色
    */
    private Color getRandColor(int fc, int bc) {
        int r = fc + random.nextInt(bc - fc - 16);
        int g = fc + random.nextInt(bc - fc - 14);
        int b = fc + random.nextInt(bc - fc - 18);
        return new Color(r, g, b);
    }


    /*
    * 绘制字符串
    */
    private void drewString(Graphics g, int i) {
        g.setFont(font);
        g.setColor(new Color(random.nextInt(101), random.nextInt(200), random.nextInt(121)));
        String rand = String.valueOf(getRandomString(random.nextInt(randString.length())));
        this.code += rand;
        g.translate(random.nextInt(3), random.nextInt(3));
        g.drawString(rand, 13 * i, 16);
    }

    /*
    * 绘制干扰线
    */
    private void drewLine(Graphics g) {
        int x = random.nextInt(width);
        int y = random.nextInt(height);
        int xl = random.nextInt(13);
        int yl = random.nextInt(15);
        g.drawLine(x, y, x + xl, y + yl);
    }

    /*
    * 获取随机的字符
    */
    public String getRandomString(int num) {
        return String.valueOf(randString.charAt(num));
    }
}