Detailed introduction to Java code examples for generating verification codes

This article introduces the process and method of generating verification codes in Java. It has a very good reference value, let’s take a look with the editor below

The process of generating verification code in Java is:

Received Request->Random number used to generate verification code->Use random number to write picture->Record random number into Session->Output verification code

# #Java The process of verifying the verification code is:

##Receive the request->Get the verification code number passed by the user->Verify whether it is correct->Output the verification result The following is an example to show the verification code generation process. This example uses the Rest interface of the basic Java Spring framework, and any platform can be used to obtain the verification code:

Example of server processing verification code:

1. Receive verification code request:

/**
 * 接收验证码请求
 */
@RequestMapping(value="captchacode")
public void CaptchaCode(){
  try {
    CaptchaCodeModel captchaCodeModel=new CaptchaCode().getCode();
    //将验证码放到Session中
    HttpServletRequest httpServletRequest=super.getRequest();
    httpServletRequest.getSession().setAttribute("captchacodekey", captchaCodeModel.getCaptchaCode());
    //将图片写到客户端 
    HttpServletResponse httpServletResponse=super.getResponse();
    //禁止缓存
    httpServletResponse.setHeader("Pragma", "no-cache");
    httpServletResponse.setHeader("Cache-Control", "no-cache");
    httpServletResponse.setDateHeader("Expires", 0);
    ServletOutputStream servletOutputStream=httpServletResponse.getOutputStream();
    //输出图片
    ImageIO.write(captchaCodeModel.getCaptchaImage(), "jpeg", servletOutputStream);
    servletOutputStream.close();
  } catch (Exception e) {
    logger.info("验证码生成失败:"+e.getMessage());
  }
}

2. Generate verification code and generate image:

public class CaptchaCode {
private int width = 90;// 定义图片的width
private int height = 20;// 定义图片的height
private int codeCount = 4;// 定义图片上显示验证码的个数
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 {
  // 定义图像buffer
  BufferedImage buffImg = new BufferedImage(width, height,
      BufferedImage.TYPE_INT_RGB);
  Graphics gd = buffImg.getGraphics();
  // 创建一个随机数生成器类
  Random random = new Random();
  // 将图像填充为白色
  gd.setColor(Color.WHITE);
  gd.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。
  gd.setFont(font);
  // 画边框。
  gd.setColor(Color.BLACK);
  gd.drawRect(0, 0, width - 1, height - 1);
  // 随机产生40条干扰线，使图象中的认证码不易被其它程序探测到。
  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 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。
    gd.setColor(new Color(red, green, blue));
    gd.drawString(code, (i + 1) * xx, codeY);
    // 将产生的四个随机数组合在一起。
    randomCode.append(code);
  }
  CaptchaCodeModel captchaCodeModel=new CaptchaCodeModel();
  captchaCodeModel.setCaptchaCode(randomCode.toString());
  captchaCodeModel.setCaptchaImage(buffImg);
  return captchaCodeModel;
}
public class CaptchaCodeModel{
  //验证码的String形式
  private String captchaCode;
  //验证码的图片形式
  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:

/**
* 验证验证码
*/
@RequestMapping(value = "valicatpcha")
public void register_R() {
PageData pageData = super.getPageData();
  // 获取验证码
  String captchaCode = pageData.getString("captchacode");
  HttpServletRequest httpServletRequest = super.getRequest();
  Object codeObject = httpServletRequest.getSession().getAttribute(“captchacodekey”);
  // 验证码错误
  if (codeObject == null
      || Tools.isEmptyString(captchaCode)
      || !String.valueOf(codeObject).toUpperCase()
          .equals(captchaCode.toUpperCase())) {
    setResult(
        MessageManager.getInstance().getMessage("invalidcaptcha"),
        ResultType.Error);
    return;
  }
}

##Example of page requesting verification code and verifying it:

-Requesting verification code:

-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); }
});
}

The above is the detailed introduction of code examples for Java to generate verification codes. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!

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