Java generates captcha

The process of Java generating captcha is as follows:

Received request - > Random number used to generate captcha - > Use random Numbers to write the picture - > Record the random number to Session - > Output verification code

The process of Java verification verification code is as follows:

Received request - > Gets the captCHA number sent by the user - > Verify that it is correct - > Output verification results

The captcha generation process is illustrated by an example that USES the Rest interface of the basic Java Spring framework and can be obtained using any platform:

Examples of server processing captcha:

1. Receive verification code request:

/**
 *  Receive a verification code request 
 */
@RequestMapping(value="captchacode")
public void CaptchaCode(){
  try {
    CaptchaCodeModel captchaCodeModel=new CaptchaCode().getCode();
    // Put the verification code to Session In the 
    HttpServletRequest httpServletRequest=super.getRequest();
    httpServletRequest.getSession().setAttribute("captchacodekey", captchaCodeModel.getCaptchaCode());
    // Write the image to the client  
    HttpServletResponse httpServletResponse=super.getResponse();
    // Prohibit the cache 
    httpServletResponse.setHeader("Pragma", "no-cache");
    httpServletResponse.setHeader("Cache-Control", "no-cache");
    httpServletResponse.setDateHeader("Expires", 0);
    ServletOutputStream servletOutputStream=httpServletResponse.getOutputStream();
    // The output image 
    ImageIO.write(captchaCodeModel.getCaptchaImage(), "jpeg", servletOutputStream);
    servletOutputStream.close();
  } catch (Exception e) {
    logger.info(" Captcha generation failed :"+e.getMessage());
  }
}

2. Generate captchas and images:

public class CaptchaCode {
private int width = 90;//  Defining the image width
private int height = 20;//  Defining the image height
private int codeCount = 4;//  Defines the number of captchas displayed on the image 
private int xx = 15;
private int fontHeight = 18;
private int codeY = 16;
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' };

public CaptchaCodeModel getCode() throws IOException {
  //  Define the image buffer
  BufferedImage buffImg = new BufferedImage(width, height,
      BufferedImage.TYPE_INT_RGB);
  Graphics gd = buffImg.getGraphics();
  //  create 1 Random number generator class 
  Random random = new Random();
  //  Fill the image with white 
  gd.setColor(Color.WHITE);
  gd.fillRect(0, 0, width, height);
  //  Create a font. The font size should be based on the height of the image. 
  Font font = new Font("Fixedsys", Font.BOLD, fontHeight);
  //  Set the font. 
  gd.setFont(font);
  //  Picture frame. 
  gd.setColor(Color.BLACK);
  gd.drawRect(0, 0, width - 1, height - 1);
  //  Randomly generated 40 An interference line that makes the authentication code in the image difficult to be detected by other programs. 
  gd.setColor(Color.BLACK);
  for (int i = 0; i < 40; i++) {
    int x = random.nextInt(width);
    int y = random.nextInt(height);
    int xl = random.nextInt(12);
    int yl = random.nextInt(12);
    gd.drawLine(x, y, x + xl, y + yl);
  }
  // randomCode Used to save randomly generated captcha for user authentication after login. 
  StringBuffer randomCode = new StringBuffer();
  int red = 0, green = 0, blue = 0;
  //  Randomly generated codeCount A verification code for a number. 
  for (int i = 0; i < codeCount; i++) {
    //  Get the randomly generated captCHA number. 
    String code = String.valueOf(codeSequence[random.nextInt(36)]);
    //  Generate random color components to construct color values so that each number output has a different color value. 
    red = random.nextInt(255);
    green = random.nextInt(255);
    blue = random.nextInt(255);
    //  The captcha is drawn into the image with a randomly generated color. 
    gd.setColor(new Color(red, green, blue));
    gd.drawString(code, (i + 1) * xx, codeY);
    //  Will produce the 4 Random number combination in 1 Up. 
    randomCode.append(code);
  }
  CaptchaCodeModel captchaCodeModel=new CaptchaCodeModel();
  captchaCodeModel.setCaptchaCode(randomCode.toString());
  captchaCodeModel.setCaptchaImage(buffImg);
  return captchaCodeModel;
}
public class CaptchaCodeModel{
  // The verification code String In the form of 
  private String captchaCode;
  // The image form of captcha 
  private BufferedImage captchaImage;
  public String getCaptchaCode() {
    return captchaCode;
  }
  public void setCaptchaCode(String captchaCode) {
    this.captchaCode = captchaCode;
  }
  public BufferedImage getCaptchaImage() {
    return captchaImage;
  }
  public void setCaptchaImage(BufferedImage captchaImage) {
    this.captchaImage = captchaImage;
  }
}

3. Receive the verification code from the user and verify:

/**
*  Verification verification code 
*/
@RequestMapping(value = "valicatpcha")
public void register_R() {
PageData pageData = super.getPageData();
  //  Get verification code 
  String captchaCode = pageData.getString("captchacode");
  HttpServletRequest httpServletRequest = super.getRequest();
  Object codeObject = httpServletRequest.getSession().getAttribute( " captchacodekey " );
  //  Verification code error 
  if (codeObject == null
      || Tools.isEmptyString(captchaCode)
      || !String.valueOf(codeObject).toUpperCase()
          .equals(captchaCode.toUpperCase())) {
    setResult(
        MessageManager.getInstance().getMessage("invalidcaptcha"),
        ResultType.Error);
    return;
  }
}

Page request verification code and verification examples:

- Request verification code: < img src='captchacode' style='height:32px;width:148px;'

- Verification verification code:

function validcaptchacode(captchaCode) {
$.ajax({
type : "POST",
url : "valicatpcha",
data : {
captchacode : captchaCode,
tm : new Date().getTime()
},
dataType : "json",
cache : false,
success : function(data) {
alert(data);
},
error : function(data) {
alert(data); }
});
}