how to inject plain database (without ORM) within nestJS framework?-CodePudding

I want to use NestJS framework. But prefer to write SQL queries by myself, and not use the heavy interface of ORMs.

I found some tutorials with examples of direct access to database, but they don't use the injection mechanism of NestJS. So, I'm trying to learn how to write a thin layers of controller and services provider which gives me the freedom to supply the query as a text parameter. Will appriciate your advices

CodePudding user response：

Let's assume that you want to use plain Postgres with nestJs (Without ORM).

You can perform the following steps :

Create A Separate Database Module And then create and inject Custom Provider

import { Module } from "@nestjs/common";
import { Pool } from "pg";
import { PG_CONNECTION } from "../constants";


export const PG_CONNECTION = 'PG_CONNECTION';

const dbProvider = {
  provide: PG_CONNECTION,
  useValue: new Pool({
    user: "postgres",
    host: "localhost",
    database: "somedb",
    password: "meh",
    port: 5432,
  }),
};

@Module({
  providers: [dbProvider],
  exports: [dbProvider],
})
export class DbModule {}

NOTE: Do export your custom Provider because we need this provider(service) in other modules.

After That, you can easily inject that provider(service) into any other module by Just Importing DbModule


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

After That you can easily inject the provider and can perform database operations with plain SQL query

import { Injectable, Inject } from '@nestjs/common';
import { PG_CONNECTION from './constants'; 

@Injectable()
export class AppService { 
  constructor(@Inject(PG_CONNECTION) private conn: any) {}
    
  async getUsers() { 
    const res = await this.conn.query('SELECT * FROM users');
    return res.rows;
  }


}

Hope this helps!

You can further read this article for better explanation. REFERENCE : https://medium.com/@calleja.justin/using-plain-pg-with-nest-js-617ec32ec2c4