<dependency>
  <groupId>com.baomidou</groupId>
  <artifactId>kaptcha-spring-boot-starter</artifactId>
  <version>${version}</version>
</dependency>

@RestController
@RequestMapping("/kaptcha")
public class KaptchaController {

  @Autowired
  private Kaptcha kaptcha;

  @GetMapping("/render")
  public void render() {
    kaptcha.render();
  }

  @PostMapping("/valid")
  public void validDefaultTime(@RequestParam String code) {
    //default timeout 900 seconds
    kaptcha.validate(code);
  }

  @PostMapping("/validTime")
  public void validCustomTime(@RequestParam String code) {
    kaptcha.validate(code, 60);
  }

}

KaptchaException  //super Exception

KaptchaIncorrectException

KaptchaNotFoundException

KaptchaTimeoutException

KaptchaRenderException //If something is wrong then Image.write when render.

import com.baomidou.kaptcha.exception.KaptchaException;
import com.baomidou.kaptcha.exception.KaptchaIncorrectException;
import com.baomidou.kaptcha.exception.KaptchaNotFoundException;
import com.baomidou.kaptcha.exception.KaptchaTimeoutException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

@RestControllerAdvice
public class GlobalExceptionHandler {

  @ExceptionHandler(value = KaptchaException.class)
  public String kaptchaExceptionHandler(KaptchaException kaptchaException) {
    if (kaptchaException instanceof KaptchaIncorrectException) {
      return "验证码不正确";
    } else if (kaptchaException instanceof KaptchaNotFoundException) {
      return "验证码未找到";
    } else if (kaptchaException instanceof KaptchaTimeoutException) {
      return "验证码过期";
    } else {
      return "验证码渲染失败";
    }

  }

}

kaptcha:
  height: 50
  width: 200
  content:
    length: 4
    source: abcdefghjklmnopqrstuvwxyz23456789
    space: 2
  font:
    color: black
    name: Arial
    size: 40
  background-color:
    from: lightGray
    to: white
  border:
    enabled: true
    color: black
    thickness: 1