NestJS 专家

资深 NestJS 专家，精通企业级、可扩展的 TypeScript 后端应用开发。

核心工作流程

1. 分析需求 — 识别模块、端点、实体及其关系
2. 设计结构 — 规划模块组织和模块间依赖
3. 实现 — 创建模块、服务和控制器，正确配置依赖注入
4. 安全加固 — 添加守卫、验证管道和认证机制
5. 验证 — 运行 npm run lint、npm run test，通过 nest info 确认 DI 图
6. 测试 — 为服务编写单元测试，为控制器编写端到端测试

参考指南

根据上下文加载详细指导：

| 主题 | 参考文档 | 加载时机 | |------|----------|----------| | 控制器 | references/controllers-routing.md | 创建控制器、路由、Swagger 文档 | | 服务 | references/services-di.md | 服务、依赖注入、提供者 | | DTO | references/dtos-validation.md | 验证、class-validator、DTO | | 认证 | references/authentication.md | JWT、Passport、守卫、授权 | | 测试 | references/testing-patterns.md | 单元测试、端到端测试、模拟 | | Express 迁移 | references/migration-from-express.md | 从 Express.js 迁移到 NestJS |

代码示例

带 DTO 验证和 Swagger 的控制器

// create-user.dto.ts
import { IsEmail, IsString, MinLength } from 'class-validator';
import { ApiProperty } from '@nestjs/swagger';

export class CreateUserDto {
  @ApiProperty({ example: 'user@example.com' })
  @IsEmail()
  email: string;

  @ApiProperty({ example: 'strongPassword123', minLength: 8 })
  @IsString()
  @MinLength(8)
  password: string;
}

// users.controller.ts
import { Body, Controller, Post, HttpCode, HttpStatus } from '@nestjs/common';
import { ApiCreatedResponse, ApiTags } from '@nestjs/swagger';
import { UsersService } from './users.service';
import { CreateUserDto } from './dto/create-user.dto';

@ApiTags('users')
@Controller('users')
export class UsersController {
  constructor(private readonly usersService: UsersService) {}

  @Post()
  @HttpCode(HttpStatus.CREATED)
  @ApiCreatedResponse({ description: 'User created successfully.' })
  create(@Body() createUserDto: CreateUserDto) {
    return this.usersService.create(createUserDto);
  }
}

带依赖注入和错误处理的服务

// users.service.ts
import { Injectable, ConflictException, NotFoundException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { User } from './entities/user.entity';
import { CreateUserDto } from './dto/create-user.dto';

@Injectable()
export class UsersService {
  constructor(
    @InjectRepository(User)
    private readonly usersRepository: Repository<User>,
  ) {}

  async create(createUserDto: CreateUserDto): Promise<User> {
    const existing = await this.usersRepository.findOneBy({ email: createUserDto.email });
    if (existing) {
      throw new ConflictException('Email already registered');
    }
    const user = this.usersRepository.create(createUserDto);
    return this.usersRepository.save(user);
  }

  async findOne(id: number): Promise<User> {
    const user = await this.usersRepository.findOneBy({ id });
    if (!user) {
      throw new NotFoundException(`User #${id} not found`);
    }
    return user;
  }
}

模块定义

// users.module.ts
import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';
import { UsersController } from './users.controller';
import { UsersService } from './users.service';
import { User } from './entities/user.entity';

@Module({
  imports: [TypeOrmModule.forFeature([User])],
  controllers: [UsersController],
  providers: [UsersService],
  exports: [UsersService], // export only when other modules need this service
})
export class UsersModule {}

服务单元测试

// users.service.spec.ts
import { Test, TestingModule } from '@nestjs/testing';
import { getRepositoryToken } from '@nestjs/typeorm';
import { ConflictException } from '@nestjs/common';
import { UsersService } from './users.service';
import { User } from './entities/user.entity';

const mockRepo = {
  findOneBy: jest.fn(),
  create: jest.fn(),
  save: jest.fn(),
};

describe('UsersService', () => {
  let service: UsersService;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      providers: [
        UsersService,
        { provide: getRepositoryToken(User), useValue: mockRepo },
      ],
    }).compile();
    service = module.get<UsersService>(UsersService);
    jest.clearAllMocks();
  });

  it('throws ConflictException when email already exists', async () => {
    mockRepo.findOneBy.mockResolvedValue({ id: 1, email: 'user@example.com' });
    await expect(
      service.create({ email: 'user@example.com', password: 'pas```