package com.example.springbootdemo.webflux.restful;

import org.springframework.stereotype.Component;
import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;

@Component
public class PersonValidator implements Validator {

  @Override
  public boolean supports(Class<?> clazz) {
    return Person.class.isAssignableFrom(clazz);
  }

  // 校驗參數(shù)的方法
  @Override
  public void validate(Object o, Errors errors) {
    ValidationUtils.rejectIfEmpty(errors, "name", "name.required");
    ValidationUtils.rejectIfEmpty(errors, "age", "age.required");
    Person p = (Person) o;
    if (p.getAge() != null && p.getAge() < 0) {
      errors.rejectValue("age", "negative.value");
    } else if (p.getAge() != null && p.getAge() > 200) {
      errors.rejectValue("age", "too.old");
    }
  }
}

@Slf4j
@Component
public class PersonHandler {

  @Autowired
  private PersonRepository repository;
  @Autowired
  private PersonValidator validator;

  public Mono<ServerResponse> savePerson(ServerRequest request) {
    Mono<Person> personMono = request.bodyToMono(Person.class).doOnNext(this::validate);
    return ServerResponse.ok().contentType(MediaType.APPLICATION_JSON)
        .body(this.repository.savePerson(personMono), Void.class);
  }
    
  public void validate(Person person) {
    Errors errors = new BeanPropertyBindingResult(person, Person.class.getName());
    validator.validate(person, errors);
    if (errors.hasErrors()) {
        // 拋出 http status 400 異常
      throw new ServerWebInputException(errors.toString());
    }
  }
    // .... 省略
}

@Configuration
@Slf4j
public class GlobalErrorConfig {

  private ObjectMapper objectMapper = new ObjectMapper();

  @Bean
  @Order(-2)
  public WebExceptionHandler exceptionHandler() {
    return (ServerWebExchange serverWebExchange, Throwable t) -> {
      DataBuffer dataBuffer = serverWebExchange.getResponse().bufferFactory().allocateBuffer();
      Result result = new Result();
      if (t instanceof ServerWebInputException) {
        ServerWebInputException exception = (ServerWebInputException) t;
        result.setCode(exception.getStatus().value());
        result.setMessage(exception.getReason());
      } else {
        result.setCode(HttpStatus.INTERNAL_SERVER_ERROR.value());
        result.setMessage(HttpStatus.INTERNAL_SERVER_ERROR.toString());
      }
      try {
        dataBuffer.write(objectMapper.writeValueAsBytes(result));
      } catch (JsonProcessingException e) {
        log.error(NestedExceptionUtils.buildMessage("write error", e));
      }
      ServerHttpResponse response = serverWebExchange.getResponse();
      response.setRawStatusCode(result.getCode());
      return response.writeWith(Mono.just(dataBuffer));
    };
  }
}

import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
public class Result {

  private Integer code;

  private String message;
}