/**

  * 获取登录的验证码

  * @param request

  * @param response

  */

 public void getLoginCode(HttpSession session,HttpServletRequest request,

     HttpServletResponse response) throws Exception{

     // 获取验证码以及图片

     Map<String,Object> map = CodeUtil.generateCodeAndPic();

     // 将验证码存入Session

     session.setAttribute("imageCode",map.get("code"));

     // 获取图片

     BufferedImage image = (BufferedImage) map.get("codePic");

     // 转成base64

     BASE64Encoder encoder = new BASE64Encoder();

     ByteArrayOutputStream baos = new ByteArrayOutputStream();//io流

     ImageIO.write(image, "png", baos);//写入流中

     byte[] bytes = baos.toByteArray();//转换成字节

     String png_base64 =  encoder.encodeBuffer(bytes).trim();//转换成base64串

     //删除 \r\n

     png_base64 = png_base64.replaceAll("\n", "").replaceAll("\r", "");

     Map<String,String> maps = new HashMap<>();

     maps.put("code","" + map.get("code"));

     maps.put("address",png_base64);

     JSONObject jsonObject = JSONObject.fromObject(maps);

     PrintWriter writer = response.getWriter();

     writer.print(jsonObject);

     writer.flush();

     writer.close();

 }                                        

private static int width = 180;

private static int height = 40;

private static int codeCount = 4;

private static int xx = 30;

private static int fontHeight = 36;

private static int codeY = 32;

private static 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'

};    

/**

 * 生成验证码图片

 * @return

 */

public static Map<String,Object> generateCodeAndPic(){

    //定义图像buffer

    BufferedImage bufferedImage = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);

    Graphics graphics = bufferedImage.getGraphics();

    //创建一个随机数类

    Random random = new Random();

    // 将图像填充为白色

    graphics.setColor(Color.WHITE);

    // 填充图像

    graphics.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.BOLD, fontHeight);

    // 设置字体

    graphics.setFont(font);

    // 画边框

    graphics.setColor(Color.black);

    graphics.drawRect(0,0,width-1,height-1);

    // 随机产生30条干扰线，让图形码不便于被其他程序检测到

    graphics.setColor(Color.black);

    for (int i=0;i<30;i++){

        int x = random.nextInt(width);

        int y = random.nextInt(height);

        int x1 = random.nextInt(12);

        int y1 = random.nextInt(12);

        graphics.drawLine(x,y,x + x1,y + y1);

    }

    // randomCode用于保存随机生成的二维码，便于用户登录时验证

    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++){

        // 得到随机的验证码数字

        String code = 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都不一样

        red = random.nextInt(255);

        blue = random.nextInt(255);

        green = random.nextInt(255);    

        // 用随机产生的颜色将验证码放到图像中

        graphics.setColor(new Color(red,green,blue));

        graphics.drawString(code,(i + 1) * xx,codeY);    

        // 将产生的四个随机数组合在一起

        randomCode.append(code);

    }    

    Map<String,Object> map = new HashMap<>();

    // 存放验证码

    map.put("code",randomCode);

    // 存放生成的验证码BufferedImage对象

    map.put("codePic",bufferedImage);

    return map;

}