REST API with NestJS, PostgreSQL, and TypeORM

NestJS is a progressive Node.js framework for building efficient and scalable server-side applications. In this guide, we’ll walk through setting up a NestJS project with PostgreSQL as the database and TypeORM as the ORM, and implement CRUD operations for a simple Tag entity.

blog-nest/
├── eslint.config.mjs
├── nest-cli.json
├── package.json
├── README.md
├── tsconfig.build.json
├── tsconfig.json
├── src/
│   ├── app.controller.spec.ts
│   ├── app.controller.ts
│   ├── app.module.ts
│   ├── app.service.ts
│   ├── main.ts
│   ├── ormconfig.ts
│   └── tag/
│       ├── tag.controller.ts
│       ├── tag.entity.ts
│       ├── tag.module.ts
│       └── tag.service.ts
└── test/
    ├── app.e2e-spec.ts
    └── jest-e2e.json

1. Project Setup

Install NestJS CLI and Create a Project.

npm i -g @nestjs/cli
nest new blog-nest

Install Dependencies

npm install @nestjs/typeorm typeorm pg

• @nestjs/typeorm: NestJS integration for TypeORM
• typeorm: ORM for TypeScript and JavaScript
• pg: PostgreSQL driver

2. Configure TypeORM and PostgreSQL

Create or update ormconfig.ts:

import { DataSource } from 'typeorm';

export default new DataSource({
  type: 'postgres',
  host: 'localhost',
  port: 5432,
  username: 'your_db_user',
  password: 'your_db_password',
  database: 'blog_nest',
  entities: [__dirname + '/**/*.entity{.ts,.js}'],
  synchronize: true, // Don't use in production
});

In app.module.ts, import TypeOrmModule:

import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';
import ormconfig from './ormconfig';

@Module({
  imports: [
    TypeOrmModule.forRoot(ormconfig),
    // ...other modules
  ],
})
export class AppModule {}

3. Create the Tag Entity

Create tag.entity.ts:

import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm';

@Entity({ name: 'tags' })
export class TagEntity {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;
}

4. Generate Tag Module, Service, and Controller

nest generate module tag
nest generate service tag
nest generate controller tag

5. Implement CRUD in Tag Service

tag.service.ts:

import { Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { TagEntity } from './tag.entity';

@Injectable()
export class TagService {
  constructor(
    @InjectRepository(TagEntity)
    private readonly tagRepository: Repository<TagEntity>,
  ) {}

  async getAll(): Promise<TagEntity[]> {
    return this.tagRepository.find();
  }

  async getById(id: number): Promise<TagEntity> {
    return this.tagRepository.findOneBy({ id });
  }

  async create(name: string): Promise<TagEntity> {
    const tag = this.tagRepository.create({ name });
    return this.tagRepository.save(tag);
  }

  async update(id: number, name: string): Promise<TagEntity> {
    await this.tagRepository.update(id, { name });
    return this.getById(id);
  }

  async delete(id: number): Promise<void> {
    await this.tagRepository.delete(id);
  }
}

6. Implement Tag Controller

tag.controller.ts:

import { Controller, Get, Post, Put, Delete, Param, Body } from '@nestjs/common';
import { TagService } from './tag.service';

@Controller('tags')
export class TagController {
  constructor(private readonly tagService: TagService) {}

  @Get()
  getAll() {
    return this.tagService.getAll();
  }

  @Get(':id')
  getById(@Param('id') id: number) {
    return this.tagService.getById(id);
  }

  @Post()
  create(@Body('name') name: string) {
    return this.tagService.create(name);
  }

  @Put(':id')
  update(@Param('id') id: number, @Body('name') name: string) {
    return this.tagService.update(id, name);
  }

  @Delete(':id')
  delete(@Param('id') id: number) {
    return this.tagService.delete(id);
  }
}

7. Run the Application

npm run start:dev

Your API will be available at http://localhost:3000/tags.

8. Testing the Endpoints

You can use tools like Postman or curl to test the CRUD endpoints:

• GET /tags — List all tags
• GET /tags/:id — Get a tag by ID
• POST /tags — Create a new tag ({ "name": "nestjs" })
• PUT /tags/:id — Update a tag
• DELETE /tags/:id — Delete a tag