nj-request-scope

Performant request scope dependency injection for NestJS framework using express server

Description

nj-request-scope library solves NestJs request-scope dependency injection problems:

• bubbling up the injection chain - NestJS documentation
• request-scope performance issues - NestJS documentation

This solution is based on the build-in javascript Proxy design pattern. For every request, only the proxy's target object is changed to the new request-scope instance instead of creating all injection chain objects.

Installation

npm install nj-request-scope

There are also a few peer dependencies that have to be satisfied:

    "@nestjs/common": ">8.0.0",
    "@nestjs/core": ">8.0.0",
    "@nestjs/platform-express": ">8.0.0",
    "express-http-context": "^1.2.4",
    "reflect-metadata": "^0.1.12",
    "rxjs": "^7.1.0"

Especially express-http-context which is not required by NestJS by default.

nj-request-scope was tested with NestJs 8.x & 9.x

Usage

To use nj-request-scope in NestJS module you have to add import of RequestScopeModule in the module class decorator:

import { RequestScopeModule } from 'nj-request-scope';

@Module({
    imports: [RequestScopeModule],
})

Next, there are two ways of using nj-request-scope.

1. Inject express request object into class constructor with NJRS_REQUEST token:

import { NJRS_REQUEST } from 'nj-request-scope';
[...]
constructor(@Inject(NJRS_REQUEST) private readonly request: Request) {}

2. Change class inject scope to request-scope with @RequestScope() decorator:

import { RequestScope } from 'nj-request-scope';

@Injectable()
@RequestScope()
export class RequestScopeService {

Limitations

Proxy handler implements only most common methods:

• get
• has
• set
• getPrototypeOf
• getOwnPropertyDescriptor
• ownKeys

If you need other methods implemented please feel free to contribute. ProxyHandler implementation

Example project

https://github.com/kugacz/nj-request-scope-example

License

nj-request-scope is MIT licensed.