一、认识 NestJS

NestJS 是一个基于 TypeScript 的 企业级 Node.js 框架，融合了 OOP（面向对象编程）、FP（函数式编程） 和 FRP（响应式编程） 思想。

它的核心理念是：

模块化 + 控制反转 + 装饰器驱动开发 + 高可维护性架构。

NestJS 特别适合构建：

• RESTful API 服务

• 微服务架构

• GraphQL 网关

• WebSocket 实时通信

• 企业后端系统

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二、安装与环境准备

1. 全局安装 Nest CLI

npm install -g @nestjs/cli

1. 创建项目

nest new my-nest-app

1. 启动开发服务

cd my-nest-app npm run start:dev

打开浏览器访问 http://localhost:3000 即可看到：

Hello World!

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三、项目结构

my-nest-app/ ├── src/ │ ├── app.controller.ts # 控制器（路由层） │ ├── app.service.ts # 服务层（业务逻辑） │ ├── app.module.ts # 根模块 │ └── main.ts # 程序入口 └── package.json

Nest 项目结构高度模块化。

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四、创建控制器 Controller

控制器负责接收请求、返回响应。

nest generate controller user

user.controller.ts

import { Controller, Get, Post, Body, Param } from '@nestjs/common'; @Controller('user') export class UserController { private users = []; @Get() getAll() { return this.users; } @Get(':id') getUser(@Param('id') id: number) { return this.users.find(u => u.id == id); } @Post() addUser(@Body() body: any) { const newUser = { id: this.users.length + 1, ...body }; this.users.push(newUser); return newUser; } }

运行后访问：

• GET /user

• POST /user { "name": "张三" }

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五、服务层 Service

服务层负责业务逻辑。

nest generate service user

user.service.ts

import { Injectable } from '@nestjs/common'; @Injectable() export class UserService { private users = []; findAll() { return this.users; } findOne(id: number) { return this.users.find(u => u.id === id); } create(user: any) { const newUser = { id: this.users.length + 1, ...user }; this.users.push(newUser); return newUser; } }

user.controller.ts

import { Controller, Get, Post, Param, Body } from '@nestjs/common'; import { UserService } from './user.service'; @Controller('user') export class UserController { constructor(private userService: UserService) {} @Get() getAll() { return this.userService.findAll(); } @Get(':id') getOne(@Param('id') id: number) { return this.userService.findOne(+id); } @Post() add(@Body() body: any) { return this.userService.create(body); } }

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六、模块化结构

NestJS 的一切功能都存在于模块中。

user.module.ts

import { Module } from '@nestjs/common'; import { UserController } from './user.controller'; import { UserService } from './user.service'; @Module({ controllers: [UserController], providers: [UserService], }) export class UserModule {}

app.module.ts

import { Module } from '@nestjs/common'; import { UserModule } from './user/user.module'; @Module({ imports: [UserModule], }) export class AppModule {}

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七、DTO 数据传输对象

NestJS 推荐使用 DTO 对输入数据进行验证。

npm install class-validator class-transformer

create-user.dto.ts

import { IsString, IsInt, MinLength } from 'class-validator'; export class CreateUserDto { @IsString() @MinLength(2) name: string; @IsInt() age: number; }

user.controller.ts

import { Body, Controller, Post } from '@nestjs/common'; import { CreateUserDto } from './dto/create-user.dto'; import { UserService } from './user.service'; @Controller('user') export class UserController { constructor(private userService: UserService) {} @Post() create(@Body() dto: CreateUserDto) { return this.userService.create(dto); } }

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八、全局数据验证管道

在入口文件启用全局验证。

main.ts

import { ValidationPipe } from '@nestjs/common'; import { NestFactory } from '@nestjs/core'; import { AppModule } from './app.module'; async function bootstrap() { const app = await NestFactory.create(AppModule); app.useGlobalPipes(new ValidationPipe()); await app.listen(3000); } bootstrap();

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九、使用中间件

中间件可用于日志、认证等逻辑。

logger.middleware.ts

import { Injectable, NestMiddleware } from '@nestjs/common'; @Injectable() export class LoggerMiddleware implements NestMiddleware { use(req: Request, res: Response, next: Function) { console.log(`[${req.method}] ${req.url}`); next(); } }

app.module.ts

import { MiddlewareConsumer, Module, NestModule } from '@nestjs/common'; import { LoggerMiddleware } from './logger.middleware'; import { UserModule } from './user/user.module'; @Module({ imports: [UserModule], }) export class AppModule implements NestModule { configure(consumer: MiddlewareConsumer) { consumer.apply(LoggerMiddleware).forRoutes('*'); } }

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十、依赖注入（DI）

NestJS 通过构造函数自动注入依赖。

@Injectable() export class EmailService { sendEmail(to: string, subject: string) { console.log(`发送邮件到：${to}，主题：${subject}`); } } @Injectable() export class UserService { constructor(private emailService: EmailService) {} create(user: any) { this.emailService.sendEmail(user.email, '欢迎注册'); } }

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十一、配置环境变量

npm install @nestjs/config

app.module.ts

import { ConfigModule } from '@nestjs/config'; @Module({ imports: [ConfigModule.forRoot()], }) export class AppModule {}

使用方式：

import { ConfigService } from '@nestjs/config'; constructor(private configService: ConfigService) { const dbHost = this.configService.get('DB_HOST'); }

.env

DB_HOST=localhost DB_PORT=3306

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十二、连接数据库（TypeORM + MySQL）

npm install @nestjs/typeorm typeorm mysql2

app.module.ts

import { TypeOrmModule } from '@nestjs/typeorm'; @Module({ imports: [ TypeOrmModule.forRoot({ type: 'mysql', host: 'localhost', port: 3306, username: 'root', password: '123456', database: 'nestdb', autoLoadEntities: true, synchronize: true, }), ], }) export class AppModule {}

user.entity.ts

import { Entity, Column, PrimaryGeneratedColumn } from 'typeorm'; @Entity() export class User { @PrimaryGeneratedColumn() id: number; @Column() name: string; @Column() age: number; }

user.module.ts

import { TypeOrmModule } from '@nestjs/typeorm'; import { User } from './user.entity'; @Module({ imports: [TypeOrmModule.forFeature([User])], })

user.service.ts

import { Injectable } from '@nestjs/common'; import { InjectRepository } from '@nestjs/typeorm'; import { Repository } from 'typeorm'; import { User } from './user.entity'; @Injectable() export class UserService { constructor(@InjectRepository(User) private repo: Repository<User>) {} findAll() { return this.repo.find(); } create(user: Partial<User>) { return this.repo.save(user); } }

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十三、异常处理与拦截器

import { ExceptionFilter, Catch, ArgumentsHost, HttpException } from '@nestjs/common'; @Catch(HttpException) export class HttpErrorFilter implements ExceptionFilter { catch(exception: HttpException, host: ArgumentsHost) { const ctx = host.switchToHttp(); const res = ctx.getResponse(); const status = exception.getStatus(); res.status(status).json({ statusCode: status, message: exception.message, timestamp: new Date().toISOString(), }); } }

main.ts

app.useGlobalFilters(new HttpErrorFilter());

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十四、守卫（Guard）实现权限控制

import { CanActivate, ExecutionContext, Injectable } from '@nestjs/common'; @Injectable() export class AuthGuard implements CanActivate { canActivate(context: ExecutionContext): boolean { const req = context.switchToHttp().getRequest(); return req.headers.token === 'secret123'; } }

controller.ts

@UseGuards(AuthGuard) @Get() getAll() { return this.userService.findAll(); }

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十五、全局拦截器

import { Injectable, NestInterceptor, ExecutionContext, CallHandler } from '@nestjs/common'; import { map } from 'rxjs/operators'; @Injectable() export class TransformInterceptor implements NestInterceptor { intercept(context: ExecutionContext, next: CallHandler) { return next.handle().pipe(map(data => ({ code: 0, data }))); } }

main.ts

app.useGlobalInterceptors(new TransformInterceptor());

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十六、Swagger 自动文档

npm install @nestjs/swagger swagger-ui-express

main.ts

import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger'; const config = new DocumentBuilder() .setTitle('NestJS API') .setDescription('自动生成的API文档') .setVersion('1.0') .build(); const document = SwaggerModule.createDocument(app, config); SwaggerModule.setup('docs', app, document);

访问 http://localhost:3000/docs 查看可视化接口文档。

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十七、WebSocket 实时通信

npm install @nestjs/websockets @nestjs/platform-socket.io

chat.gateway.ts

import { WebSocketGateway, SubscribeMessage, MessageBody } from '@nestjs/websockets'; @WebSocketGateway() export class ChatGateway { @SubscribeMessage('message') handleMessage(@MessageBody() msg: string): string { console.log('收到消息：', msg); return '服务器回复：' + msg; } }

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十八、任务调度（CronJob）

npm install @nestjs/schedule

app.module.ts

import { ScheduleModule } from '@nestjs/schedule'; @Module({ imports: [ScheduleModule.forRoot()], }) export class AppModule {}

task.service.ts

import { Injectable } from '@nestjs/common'; import { Cron } from '@nestjs/schedule'; @Injectable() export class TaskService { @Cron('*/5 * * * * *') handleTask() { console.log('每5秒执行一次任务'); } }

参考案例：www.yllbn.cn

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十九、JWT 登录认证

npm install @nestjs/jwt passport-jwt @nestjs/passport

登录后生成 Token：

import { JwtService } from '@nestjs/jwt'; constructor(private jwt: JwtService) {} login(user: any) { const payload = { username: user.name }; return { token: this.jwt.sign(payload) }; }

守卫验证：

@UseGuards(AuthGuard('jwt')) @Get('profile') getProfile() { return { user: '张三' }; }

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二十、完整实战项目：留言板后端 API

message.entity.ts

import { Entity, Column, PrimaryGeneratedColumn } from 'typeorm'; @Entity() export class Message { @PrimaryGeneratedColumn() id: number; @Column() author: string; @Column() content: string; }

message.service.ts

@Injectable() export class MessageService { constructor(@InjectRepository(Message) private repo: Repository<Message>) {} create(msg: Partial<Message>) { return this.repo.save(msg); } findAll() { return this.repo.find(); } }

message.controller.ts

@Controller('message') export class MessageController { constructor(private msgService: MessageService) {} @Get() findAll() { return this.msgService.findAll(); } @Post() create(@Body() body: any) { return this.msgService.create(body); } }

运行项目后：

• POST /message 添加留言

• GET /message 获取留言