JavaWeb验证码

// 集合中保存所有成语
private List<String> words = new ArrayList<String>();

@Override
public void init() throws ServletException {
    // 初始化阶段，读取new_words.txt
    // web工程中读取 文件，必须使用绝对磁盘路径
    String path = getServletContext().getRealPath("/WEB-INF/new_words.txt");
    try {
        BufferedReader reader = new BufferedReader(new FileReader(path));
        String line;
        while ((line = reader.readLine()) != null) {
            words.add(line);
        }
        reader.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    // 禁止缓存
    // response.setHeader("Cache-Control", "no-cache");
    // response.setHeader("Pragma", "no-cache");
    // response.setDateHeader("Expires", -1);

    int width = 120;
    int height = 30;

    // 步骤一 绘制一张内存中图片
    BufferedImage bufferedImage = new BufferedImage(width, height,
            BufferedImage.TYPE_INT_RGB);

    // 步骤二 图片绘制背景颜色 ---通过绘图对象
    Graphics graphics = bufferedImage.getGraphics();// 得到画图对象 --- 画笔
    // 绘制任何图形之前 都必须指定一个颜色
    graphics.setColor(getRandColor(200, 250));
    graphics.fillRect(0, 0, width, height);

    // 步骤三 绘制边框
    graphics.setColor(Color.WHITE);
    graphics.drawRect(0, 0, width - 1, height - 1);

    // 步骤四 四个随机数字
    Graphics2D graphics2d = (Graphics2D) graphics;
    // 设置输出字体
    graphics2d.setFont(new Font("宋体", Font.BOLD, 18));

    Random random = new Random();// 生成随机数
    int index = random.nextInt(words.size());
    String word = words.get(index);// 获得成语

    // 定义x坐标
    int x = 10;
    for (int i = 0; i < word.length(); i++) {
        // 随机颜色
        graphics2d.setColor(new Color(20 + random.nextInt(110), 20 + random
                .nextInt(110), 20 + random.nextInt(110)));
        // 旋转 -30 --- 30度
        int jiaodu = random.nextInt(60) - 30;
        // 换算弧度
        double theta = jiaodu * Math.PI / 180;

        // 获得字母数字
        char c = word.charAt(i);

        // 将c 输出到图片
        graphics2d.rotate(theta, x, 20);
        graphics2d.drawString(String.valueOf(c), x, 20);
        graphics2d.rotate(-theta, x, 20);
        x += 30;
    }

    // 将验证码内容保存session
    request.getSession().setAttribute("checkcode_session", word);

    // 步骤五 绘制干扰线
    graphics.setColor(getRandColor(160, 200));
    int x1;
    int x2;
    int y1;
    int y2;
    for (int i = 0; i < 30; i++) {
        x1 = random.nextInt(width);
        x2 = random.nextInt(12);
        y1 = random.nextInt(height);
        y2 = random.nextInt(12);
        graphics.drawLine(x1, y1, x1 + x2, x2 + y2);
    }

    // 将上面图片输出到浏览器 ImageIO
    graphics.dispose();// 释放资源

    //将图片写到response.getOutputStream()中
    ImageIO.write(bufferedImage, "jpg", response.getOutputStream());

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    doGet(request, response);
}

/**
 * 取其某一范围的color
 *
 * @param fc
 *            int 范围参数1
 * @param bc
 *            int 范围参数2
 * @return Color
 */
private Color getRandColor(int fc, int bc) {
    // 取其随机颜色
    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);
}

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https://github.com/FoxconnPeter