为什么DTO没有在nestjs中抛出验证错误？

import { Injectable, NestMiddleware, HttpException, HttpStatus } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';
import { validate } from 'class-validator';

@Injectable()
export class ValidationMiddleware implements NestMiddleware {
  async use(req: Request, res: Response, next: NextFunction) {
    const dto = req.body; // 获取DTO对象

    const errors = await validate(dto); // 验证DTO

    if (errors.length > 0) {
      // 如果有验证错误，则抛出异常
      const errorMessage = errors.map(error => Object.values(error.constraints).join(', ')).join(', ');
      throw new HttpException(errorMessage, HttpStatus.BAD_REQUEST);
    }

    next();
  }
}

import { Controller, Post, UseMiddleware } from '@nestjs/common';
import { ValidationMiddleware } from './validation.middleware';
import { CreateDto } from './create.dto';

@Controller('example')
export class ExampleController {
  @Post()
  @UseMiddleware(ValidationMiddleware)
  create(@Body() dto: CreateDto) {
    // 处理业务逻辑
  }
}