NestJS入门

NestJS是基于NodeJS的服务端框架。

官方文档：NestJS中文官网

环境准备

nodejs环境 官网要求版本 >= 20 ，全局安装NestJS CLI

npm i -g @nestjs/cli

安装完成后，我们可以通过命令检测安装是否成功

nest -h

如果出现以下内容，则为安装成功

Usage: nest <command> [options]

Options:
  -v, --version                                   Output the current version.
  -h, --help                                      Output usage information.

Commands:
  new|n [options] [name]                          Generate Nest application.
  build [options] [app]                           Build Nest application.
  start [options] [app]                           Run Nest application.
  generate|g [options] <schematic> [name] [path]  Generate a Nest element.
    Available schematics:
      ┌───────────────┬─────────────┐
      │ name          │ alias       │
      │ application   │ application │
      │ angular-app   │ ng-app      │
      │ class         │ cl          │
      │ configuration │ config      │
      │ controller    │ co          │
      │ decorator     │ d           │
      │ filter        │ f           │
      │ gateway       │ ga          │
      │ guard         │ gu          │
      │ interceptor   │ in          │
      │ interface     │ interface   │
      │ middleware    │ mi          │
      │ module        │ mo          │
      │ pipe          │ pi          │
      │ provider      │ pr          │
      │ resolver      │ r           │
      │ service       │ s           │
      │ library       │ lib         │
      │ sub-app       │ app         │
      └───────────────┴─────────────┘
  info|i                                          Display Nest project details.
  update|u [options]                              Update Nest dependencies.
  add [options] <library>                         Adds support for an external library to your project.

创建项目

命令行切换至你想要创建项目的目录下，执行

nest new my-nest-project
cd my-nest-project
npm i          
npm run start

项目主要结构

src/
├── app.controller.spec.ts    # 控制器测试文件
├── app.controller.ts         # 基础控制器
├── app.module.ts            # 根模块
├── app.service.ts           # 基础服务
└── main.ts                  # 应用入口文件

核心模块

1.控制器Controllors

控制器负责处理传来的请求和向客户端返回响应

// src/app.controller.ts
import { Controller, Get, Post, Body } from '@nestjs/common';
import { AppService } from './app.service';

@Controller('api')
export class AppController {
  constructor(private readonly appService: AppService) {}

  @Get('hello')
  getHello(): string {
    return this.appService.getHello();
  }

  @Post('message')
  createMessage(@Body() message: { content: string }) {
    return this.appService.createMessage(message);
  }
}

2.提供者Providers

提供者是 NestJS 中的基础概念，多数情况下用于封装业务逻辑

// src/app.service.ts
import { Injectable } from '@nestjs/common';

@Injectable()
export class AppService {
  private messages: string[] = [];

  getHello(): string {
    return 'Hello World!';
  }

  createMessage(message: { content: string }): string {
    this.messages.push(message.content);
    return `Message created: ${message.content}`;
  }

  getAllMessages(): string[] {
    return this.messages;
  }
}

3.模块Modules

模块是用来组织应用程序结构的基本单位

// src/app.module.ts
import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';

@Module({
  imports: [],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

4.中间件Middleware

中间件是在路由处理程序之前调用的函数

// src/common/middleware/logger.middleware.ts
import { Injectable, NestMiddleware } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';

@Injectable()
export class LoggerMiddleware implements NestMiddleware {
  use(req: Request, res: Response, next: NextFunction) {
    console.log(`Request... Method: ${req.method}, Path: ${req.path}`);
    next();
  }
}

// 在模块中应用中间件
// src/app.module.ts
import { Module, NestModule, MiddlewareConsumer } from '@nestjs/common';
import { LoggerMiddleware } from './common/middleware/logger.middleware';

@Module({
  // ... 其他配置
})
export class AppModule implements NestModule {
  configure(consumer: MiddlewareConsumer) {
    consumer
      .apply(LoggerMiddleware)
      .forRoutes('*');
  }
}

5.管道Pipes

管道用于数据转换和验证

// src/common/pipes/validation.pipe.ts
import { PipeTransform, Injectable, ArgumentMetadata, BadRequestException } from '@nestjs/common';
import { validate } from 'class-validator';
import { plainToClass } from 'class-transformer';

@Injectable()
export class ValidationPipe implements PipeTransform<any> {
  async transform(value: any, { metatype }: ArgumentMetadata) {
    if (!metatype || !this.toValidate(metatype)) {
      return value;
    }
    const object = plainToClass(metatype, value);
    const errors = await validate(object);
    if (errors.length > 0) {
      throw new BadRequestException('Validation failed');
    }
    return value;
  }

  private toValidate(metatype: Function): boolean {
    const types: Function[] = [String, Boolean, Number, Array, Object];
    return !types.includes(metatype);
  }
}

6.异常过滤器Exception Filters

用于处理应用程序中的异常

// src/common/filters/http-exception.filter.ts
import { ExceptionFilter, Catch, ArgumentsHost, HttpException } from '@nestjs/common';
import { Request, Response } from 'express';

@Catch(HttpException)
export class HttpExceptionFilter implements ExceptionFilter {
  catch(exception: HttpException, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse<Response>();
    const request = ctx.getRequest<Request>();
    const status = exception.getStatus();

    response
      .status(status)
      .json({
        statusCode: status,
        timestamp: new Date().toISOString(),
        path: request.url,
        message: exception.message,
      });
  }
}

7.守卫Guards

守卫用于处理授权逻辑

// src/common/guards/auth.guard.ts
import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';
import { Observable } from 'rxjs';

@Injectable()
export class AuthGuard implements CanActivate {
  canActivate(
    context: ExecutionContext,
  ): boolean | Promise<boolean> | Observable<boolean> {
    const request = context.switchToHttp().getRequest();
    // 在这里实现你的授权逻辑
    return true; // 或 false
  }
}

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本文作者：Ray
本文链接：NestJS入门
如有错误，请及时评论或者 B 站私信哦~

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最后更新于:2024/01/28

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