如何在验证失败时设置回退值(NestJS，类验证器)

npm install class-validator class-transformer

import { IsString, IsNotEmpty } from 'class-validator';

export class CreateUserDto {
  @IsString()
  @IsNotEmpty()
  username: string;

  @IsString()
  @IsNotEmpty()
  password: string;
}

import { Controller, Post, Body } from '@nestjs/common';
import { CreateUserDto } from './dto/create-user.dto';
import { ValidationException } from './exceptions/validation.exception';

@Controller('users')
export class UsersController {
  @Post()
  createUser(@Body() createUserDto: CreateUserDto) {
    const errors = await validate(createUserDto);
    if (errors.length > 0) {
      throw new ValidationException('Validation failed', errors);
    }

    // 处理创建用户的逻辑
  }
}

import { ExceptionFilter, Catch, ArgumentsHost } from '@nestjs/common';
import { ValidationException } from './exceptions/validation.exception';

@Catch(ValidationException)
export class ValidationExceptionFilter implements ExceptionFilter {
  catch(exception: ValidationException, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse();

    response.status(400).json({
      statusCode: 400,
      message: exception.message,
      errors: exception.errors,
    });
  }
}

import { Module } from '@nestjs/common';
import { APP_FILTER } from '@nestjs/core';
import { ValidationExceptionFilter } from './filters/validation-exception.filter';

@Module({
  providers: [
    {
      provide: APP_FILTER,
      useClass: ValidationExceptionFilter,
    },
  ],
})
export class AppModule {}