1. Nest.js

• Lifecycle
  • onModuleInit -> onApplicationBootstrap
  • onModuleDestroy -> onApplicationShutdown
• OVERVIEW
  1. Controllers
     • Request payloads: [DTO classes](https://docs.nestjs.com/controllers#request-payloads:~:text=A DTO is,variable at runtime.)
  2. Providers
     1. SOLID + Github, principle
     2. Dependency Injection(DI): One of Inversion of Control(IoC)
        1. Why DI: loosely coupled → fewer bugs and easier testing
     3. how to inject the provider
     4. Custom providers
  3. Modules
     1. Global module: If you have to import the same set of modules everywhere, Global modules should be registered only once, generally by the root or core module.
  4. Guards(with SECURITY-Authentication, RECIPES-Passport)
     1. Guard
        1. canActivate: logic to determine if the route should proceed or not. (verify JWT)
        2. Roles
     2. Passport
        1. Strategy
           • constructor: extract method and options
           • [validate](https://docs.nestjs.com/recipes/passport#:~:text=you verify whether a user exists (and/or create a new user)%2C and whether their credentials are valid.): you can add more validation logic or attach additional user data to the request.
  5. Interceptors
     1. Aspect-Oriented Programming: a way to pull out "repetitive code" (like logging, security, or error handling) that is scattered across your entire application and manage it in one single place
  6. Custom decorators
     1. why need it: [reusable](https://docs.nestjs.com/custom-decorators#:~:text=reuse it across all of your controllers.)
• TECHNIQUES
  1. [Serialization](https://docs.nestjs.com/techniques/serialization#:~:text=Serialization is a process that happens before objects are returned in a network response.)
     1. sensitive data like passwords should always be excluded from the response.
     2. class-transformer
     3. 객체 안에 객체를 어떻게 접근할까?
  2. [Server-Sent Events](https://docs.nestjs.com/techniques/server-sent-events#:~:text=a server push technology enabling a client to receive automatic updates from a server via HTTP connection.)
     1. Notification
• SECURITY
  1. Authentication: JSON Web Token(JWT token), Refresh JWT
     1. JWT: Header.Payload.Signature for Access Token, Refresh Token
• RECIPES
  1. RouterModule: Routing defining a prefix at a module-level may come in handy.
  2. Passport
• FAQ
  1. Request lifecycle
     1. Middleware
     2. Guards
     3. Interceptors
     4. Pipes
     5. Filters: standard error message and semantic(RFC 7807), microservices

• Request lifecycle

  • Middleware: HTTP 요청과 응답 사이에서 단계별 동작을 수행하기 위해.

  • Pipe: for data transformation(e.g., from string to integer) and validation.

    • pipe throws an error, it skips the interceptor❓ → while I was studying the filter. filter is standard error message and last defenser.

    파이프

• Configuration

  Configuration

• Task scheduler(Cron)

  • 주기적으로 반복적인 작업을 처리하기 위해.
  • reference(kor)

• Overview

  • custom decorators: use cases

• Techniques

2. TypeORM

Nest.js database

• multiple databases
• Mapping: 1:1, 1:N, N:1, N:M → 관계형 데이터베이스를 위한 매핑.
• Datasource(v0.3.x)와 @InjectRepository()의 차이점: 성능으로 별 차이 없는 것 같음.
  • Access flow: DataSource → EntityManager → Repository
    • EntityManager is just like a collection of all entity repositories in a single place. You can access the entity manager via DataSource.
    • Repository is just like EntityManager but its operations are limited to a concrete entity. You can access the repository via EntityManager.