登录验证码图片生成

// 验证码图片的宽度。         
    private int width = 60;         
    // 验证码图片的高度。         
    private int height = 20;         
    // 验证码字符个数         
    private int codeCount = 4;         
    private int x = 0;         
    // 字体高度         
    private int fontHeight;         
    private int codeY;         
    char[] codeSequence = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',         
            'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',         
            'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };    
    /**
     * 生成验证码
     * @param mapping
     * @param form
     * @param request
     * @param response
     * @return null
     * @author gjm 2015-12-10 09:38:00
     */
    public ActionForward yzmImg(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response) {
        // 宽度         
        String strWidth ="70";         
        // 高度         
        String strHeight ="20";         
        // 字符个数         
        String strCodeCount = "4";         
        // 将配置的信息转换成数值         
        try {         
            if (strWidth != null && strWidth.length() != 0) {         
                width = Integer.parseInt(strWidth);         
            }         
            if (strHeight != null && strHeight.length() != 0) {         
                height = Integer.parseInt(strHeight);         
            }         
            if (strCodeCount != null && strCodeCount.length() != 0) {         
                codeCount = Integer.parseInt(strCodeCount);         
            }         
        } catch (NumberFormatException e) {         
        }         
        x = width / (codeCount + 1);         
        fontHeight = height - 2;         
        codeY = height - 4;    
        
     // 定义图像buffer         
        BufferedImage buffImg = new BufferedImage(width, height,         
                BufferedImage.TYPE_INT_RGB);         
        Graphics2D g = buffImg.createGraphics();         
        // 创建一个随机数生成器类         
        Random random = new Random();         
        // 将图像填充为白色         
        g.setColor(Color.WHITE);         
        g.fillRect(0, 0, width, height);         
        // 创建字体，字体的大小应该根据图片的高度来定。         
        Font font = new Font("Fixedsys", Font.PLAIN, fontHeight);         
        // 设置字体。         
        g.setFont(font);         
        // 画边框。         
        g.setColor(Color.BLACK);         
        g.drawRect(0, 0, width - 1, height - 1);         
        // 随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。         
        g.setColor(Color.BLACK);         
        for (int i = 0; i < 10; i++) {         
            int x = random.nextInt(width);         
            int y = random.nextInt(height);         
            int xl = random.nextInt(12);         
            int yl = random.nextInt(12);         
            g.drawLine(x, y, x + xl, y + yl);         
        }         
        // randomCode用于保存随机产生的验证码，以便用户登录后进行验证。         
        StringBuffer randomCode = new StringBuffer();         
        int red = 0, green = 0, blue = 0;         
        // 随机产生codeCount数字的验证码。         
        for (int i = 0; i < codeCount; i++) {         
            // 得到随机产生的验证码数字。         
            String strRand = String.valueOf(codeSequence[random.nextInt(36)]);         
            // 产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同。         
            red = random.nextInt(255);         
            green = random.nextInt(255);         
            blue = random.nextInt(255);         
            // 用随机产生的颜色将验证码绘制到图像中。         
            g.setColor(new Color(red, green, blue));         
            g.drawString(strRand, (i + 1) * x, codeY);         
            // 将产生的四个随机数组合在一起。         
            randomCode.append(strRand);         
        }         
        // 将四位数字的验证码保存到Session中。         
        HttpSession session = request.getSession();         
        session.setAttribute("yzmCode", randomCode.toString());         
        // 禁止图像缓存。         
        response.setHeader("Pragma", "no-cache");         
        response.setHeader("Cache-Control", "no-cache");         
        response.setDateHeader("Expires", 0);         
        response.setContentType("image/jpeg");         
        // 将图像输出到Servlet输出流中。         
        ServletOutputStream sos=null;
        try {
            sos = response.getOutputStream();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }         
        try {
            ImageIO.write(buffImg, "jpeg", sos);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }         
        try {
            sos.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }         
            
        return null;
        
    }