Nest 的中间件 Middleware ？

新建项目

nest new middleware-demo

创建一个中间件

nest g middleware aaa --no-spec --flat

加下打印

import { Injectable, NestMiddleware } from '@nestjs/common';
import { Request, Response } from 'express';

@Injectable()
export class AaaMiddleware implements NestMiddleware {
  use(req: Request, res: Response, next: () => void) {
    console.log('brefore');
    next();
    console.log('after');
  }
}

在 Module 里这样使用

import { MiddlewareConsumer, Module, NestModule } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { AaaMiddleware } from './aaa.middleware';

@Module({
  imports: [],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule implements NestModule {
  configure(consumer: MiddlewareConsumer) {
    consumer.apply(AaaMiddleware).forRoutes('*');
  }
}

跑起来看看

可以指定更精确的路由，添加几个 handler

import { Controller, Get } from '@nestjs/common';
import { AppService } from './app.service';

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

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

  @Get('hello2')
  getHello2(): string {
    console.log('hello2');
    return this.appService.getHello();
  }

  @Get('hi')
  getHi(): string {
    console.log('hi');
    return this.appService.getHello();
  }

  @Get('hi1')
  getHi1(): string {
    console.log('hi1');
    return this.appService.getHello();
  }
}

module 匹配更新下

import { AaaMiddleware } from './aaa.middleware';
import {
  MiddlewareConsumer,
  Module,
  NestModule,
  RequestMethod,
} from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';

@Module({
  imports: [],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule implements NestModule {
  configure(consumer: MiddlewareConsumer) {
    consumer
      .apply(AaaMiddleware)
      .forRoutes({ path: 'hello/*path', method: RequestMethod.GET });
    consumer
      .apply(AaaMiddleware)
      .forRoutes({ path: 'hi1', method: RequestMethod.GET });
  }
}

Nest 为什么要把 Middleware 做成 class 呢？

为了依赖注入！

通过 @Inject 注入 AppService 到 middleware 里

import { AppService } from './app.service';
import { Inject, Injectable, NestMiddleware } from '@nestjs/common';
import { Request, Response } from 'express';

@Injectable()
export class AaaMiddleware implements NestMiddleware {
  @Inject(AppService)
  private readonly appService: AppService;

  use(req: Request, res: Response, next: () => void) {
    console.log('brefore');
    console.log('-------' + this.appService.getHello());
    next();
    console.log('after');
  }
}

这就是 Nest 注入的依赖