基本参数

/**
 * 随机验证码生成访问
 */
private static final String RANGE_RANDOM_STR = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

/**
 * 图片尺寸设置
 */
private static final int WIDTH = 100;
private static final int HEIGHT = 32;

/**
 * 干扰线段数量
 */
private static final int LINE_NUM = 40;

/**
 * 随机验证码个数
 */
private static final int STE_NUM = 4;

/**
 * 验证码默认字体
 */
private static final Font DEFAULT_FONT =  new Font("Times New Roman", Font.ROMAN_BASELINE, 22);

/**
 * 随机数工具
 */
private static final Random RANDOM = new Random();

获取随机字符串

public static String getRandomString() {
    StringBuffer rssb = new StringBuffer();
    for(int index = 0; index < STE_NUM; index++) {
        rssb.append(RANGE_RANDOM_STR.charAt(RANDOM.nextInt(RANGE_RANDOM_STR.length())));
    }
    return rssb.toString();
}

获得随机颜色

private static Color getRandColor(int fc, int bc) {
    if (fc > 255) fc = 255;
    if (bc > 255) bc = 255;
    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);
}

绘制干扰线

private static void drowLine(Graphics graphics) {
    int x = RANDOM.nextInt(WIDTH);
    int y = RANDOM.nextInt(HEIGHT);
    int xl = RANDOM.nextInt(13);
    int yl = RANDOM.nextInt(15);
    graphics.drawLine(x, y, x + xl, y + yl);
}

绘制字符串

private static void drowString(Graphics graphics, String randomString) {
    // 设置字体样式
    graphics.setFont(DEFAULT_FONT);
    // 设置字体颜色
    graphics.setColor(new Color(RANDOM.nextInt(101), RANDOM.nextInt(111), RANDOM.nextInt(121)));
    graphics.translate(RANDOM.nextInt(3), RANDOM.nextInt(3));
    graphics.drawString(randomString, 20, 20);
}

获取图片

/**
 * 获取图片验证码。
 */
public static BufferedImage getImage(String randomString) {
    // 创建绘图对象
    BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_BGR);
    Graphics graphics = image.getGraphics();
    // 绘图大小
    graphics.fillRect(0, 0, WIDTH, HEIGHT);
    // 字体大小
    graphics.setFont(DEFAULT_FONT);
    // 字体颜色
    graphics.setColor(getRandColor(110, 133));
    // 绘制干扰线
    for (int i = 0; i <= LINE_NUM; i++) {
        drowLine(graphics);
    }
    // 绘制随机字符串
    drowString(graphics, randomString);
    graphics.dispose();
    return image;
}

/**
 * 获取图片验证码。
 */
public static BufferedImage getImage() {
    return getImage(getRandomString());
}

HTTP响应设置

// 设置相应类型。输出的内容为图片
response.setContentType("image/jpeg");
// 设置响应头信息。不要缓存
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expire", 0);
try {
    // 根据随机字符串，生成图片对象
    String randomString = VerifyUtils.getRandomString();
    BufferedImage image = VerifyUtils.getImage(randomString);
    // 将内存中的图片通过流动形式输出到客户端
    ImageIO.write(image, "JPEG", response.getOutputStream());
} catch (IOException e) {
    LOGGER.error("IOException : {}", e.getMessage(), e);
}