验证码自动生成代码 java

 public String getCheckCode(HttpServletRequest request,HttpServletResponse response) throws Exception {
  BufferedImage bufferedImage = new BufferedImage(55, 23, BufferedImage.TYPE_INT_BGR);
  Graphics g = bufferedImage.getGraphics();
  g.setColor(new Color(247, 247, 247));
  g.fillRect(0, 0, bufferedImage.getWidth(), bufferedImage.getHeight());
  
  Random rand = new Random();
  for (int i = 0; i < 10; i++) {
   g.setColor(new Color(rand.nextInt(200), rand.nextInt(200), rand.nextInt(200)));
   g.drawLine(rand.nextInt(60), rand.nextInt(25), rand.nextInt(60), rand.nextInt(25));
  }
  
  StringBuilder code = new StringBuilder();
  for (int i = 0; i < 4; i++) {
   code.append(rand.nextInt(9));
  }
  Font f = new Font("Georgia", Font.BOLD, 18);
  g.setFont(f);
  g.setColor(Color.BLACK);
  g.drawString(code.toString(), 1, 18);
  g.dispose();
  
  ByteArrayOutputStream bos = new ByteArrayOutputStream();
  JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos);
  encoder.encode(bufferedImage);
  InputStream image = new ByteArrayInputStream(bos.toByteArray());
  request.getSession().setAttribute("imgcode", code.toString());
  ImageIO.write(bufferedImage, "JPEG", response.getOutputStream());
  return  code.toString();
 }

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@RequestMapping("/getcheckcode.htm")
 public String getcheckcode(HttpServletRequest request,HttpServletResponse response) throws Exception{
  CheckCodeUtils checkcode = new CheckCodeUtils();
  
  response.setHeader("Cache-Control", "no-cache,must-revalidate");
  response.setCharacterEncoding("UTF-8");
  String code = checkcode.getCheckCode(request,response);
  return null;
 }

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<img id="imgCode" align="absMiddle" src="" onclick="changeimgcode();" alt="看不清，点我换换看啊！" style="cursor:hand;">

 

function changeimgcode(){
 document.getElementById('imgCode').src='$!{request.contextPath}/getcheckcode.htm?'+new Date();
 }