Spring Boot @Valid校验DTO失败时抛出的实际异常类型是什么

问题描述 #

• 提交不符合校验规则的DTO请求时，全局异常处理器中配置的@ExceptionHandler(ValidationException.class)方法未触发，仅兜底的Exception类型处理器可以捕获该异常，需要明确异常实际类型以编写精准匹配的处理逻辑。
• 关闭通用异常处理器后，接口返回默认400错误响应：
  异常响应截图

关联代码 #

DTO定义 #

public class BookDto {
    
    @NotBlank(message = "Name of the book cannot be empty!")
    @Size(min = 4, max = 30, message = "Name of the book must be between 4 and 30 characters long!")
    public String name;

    @NotBlank(message = "Author of the book cannot be empty!")
    @Size(min = 4, max = 35, message = "Author of the book must be between 5 and 35 characters long!")
    public String author;

    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd")
    public LocalDate publicationYear;

    @NotNull(message = "Pages of the book cannot be null!")
    @Digits(integer = 4, fraction = 0)
    public int pagesNumber;

    @NotBlank(message = "Publisher of the book cannot be empty!")
    @Size(min = 4, max = 30, message = "Publisher of the book must be between 4 and 30 characters long!")
    public String publisher;

}

全局异常处理器定义 #

@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(ResourceNotFoundException.class)
    protected ResponseEntity<?> resourceNotFoundException(ResourceNotFoundException ex, WebRequest request) {
        ErrorDetails errorDetails = new ErrorDetails(new Date(), ex.getMessage(), request.getDescription(false));
        return new ResponseEntity<>(errorDetails, HttpStatus.NOT_FOUND);
    }

    @ExceptionHandler(ResourceWasDeletedException.class)
    protected ResponseEntity<MyGlobalExceptionHandler> handleDeleteException() {
        return new ResponseEntity<>(new MyGlobalExceptionHandler("This book was deleted!"), HttpStatus.NOT_FOUND);
    }

    @ExceptionHandler(ValidationException.class)
    public ResponseEntity<?> handleValidationException(ValidationException exception, WebRequest webRequest) {
        ErrorDetails errorDetails = new ErrorDetails(new Date(), exception.getMessage(), webRequest.getDescription(false));
        return new ResponseEntity<>(errorDetails, HttpStatus.BAD_REQUEST);
    }

    /*    @ExceptionHandler(Exception.class)
    public ResponseEntity<?> globalExceptionHandler(Exception ex, WebRequest request) {
        ErrorDetails errorDetails = new ErrorDetails(new Date(), ex.getMessage(), request.getDescription(false));
        return new ResponseEntity<>(errorDetails, HttpStatus.INTERNAL_SERVER_ERROR);
    }*/

    @Data
    @AllArgsConstructor
    private static class MyGlobalExceptionHandler {
        private String message;
    }
}

接口定义 #

@PostMapping("/books")
@ResponseStatus(HttpStatus.CREATED)
public BookDto createBook(@Valid @RequestBody BookDto requestForSave){
    var book = converter.getMapperFacade().map(requestForSave, Book.class);
    log.debug("Book={}", book);
    var bookDto = converter.toDto((Book) bookService.create(book));
    log.debug("Book={}", bookDto);
    return bookDto;
}

问题根因 #

该场景下@RequestBody标注的请求体参数校验失败时，Spring MVC抛出的异常类型为**org.springframework.web.bind.MethodArgumentNotValidException**，并非ValidationException，因此原有校验异常处理器无法匹配触发。

补充说明：ValidationException的子类ConstraintViolationException仅会在@RequestParam、@PathVariable这类非请求体参数校验失败时抛出，无法覆盖@RequestBody的校验场景。

修复方案 #

在全局异常处理器中新增MethodArgumentNotValidException类型的异常处理方法即可，示例代码如下：

@ExceptionHandler(MethodArgumentNotValidException.class)
public ResponseEntity<?> handleMethodArgInvalidException(MethodArgumentNotValidException ex, WebRequest webRequest) {
    // 提取所有字段校验错误信息
    List<String> errMsgs = ex.getBindingResult()
            .getFieldErrors()
            .stream()
            .map(FieldError::getDefaultMessage)
            .collect(Collectors.toList());
    ErrorDetails errorDetails = new ErrorDetails(new Date(), String.join("; ", errMsgs), webRequest.getDescription(false));
    return new ResponseEntity<>(errorDetails, HttpStatus.BAD_REQUEST);
}

注意：Spring Boot 2.3及以上版本需要手动引入spring-boot-starter-validation依赖，校验相关逻辑才会正常生效。

内容的提问来源于stack exchange，提问作者iank