SpringBoot Request Parameter Validation Guide

In Spring Boot, you can utilize annotations from the JSR 303 specification to validate request parameters. The specific steps are as follows:

1. Add validation annotations like @Validated and @NotBlank before the request method parameters in the Controller class.

@RestController
@RequestMapping("/api")
@Validated
public class UserController {
    
    @PostMapping("/user")
    public ResponseEntity<String> createUser(@Valid @RequestBody UserDto userDto) {
        // 处理请求参数
        return ResponseEntity.ok("User created successfully");
    }
}

1. Create a DTO class to encapsulate request parameters, and add validation annotations to the properties of the DTO class.

public class UserDto {

    @NotBlank(message = "Name is mandatory")
    private String name;

    @Email(message = "Email should be valid")
    private String email;

    // getter and setter
}

1. Define a global exception handler in the Controller class to capture validation errors and return error messages.

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(MethodArgumentNotValidException.class)
    @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ResponseBody
    public ResponseEntity<String> handleValidationException(MethodArgumentNotValidException ex) {
        BindingResult result = ex.getBindingResult();
        List<String> errorMessages = result.getAllErrors().stream()
                .map(DefaultMessageSourceResolvable::getDefaultMessage)
                .collect(Collectors.toList());
        return ResponseEntity.badRequest().body(String.join(", ", errorMessages));
    }
}

In this way, when the validation of the request parameters fails, the corresponding error message will be returned. Spring Boot automatically validates the request parameters and throws a MethodArgumentNotValidException exception when the validation fails, the global exception handler will capture this exception and return the error message.