java后台生成图片二维码

　　controller:

 /**
  * 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;
}