Config Module

The ConfigModule provides strongly-typed, environment-variable-based configuration with TypeBox schema validation.

Setup

import { Module, ConfigModule } from 'next-js-backend';
import { Type as t } from '@sinclair/typebox';

@Module({
  imports: [
    ConfigModule.register({
      schema: t.Object({
        PORT: t.Number({ default: 3000 }),
        NODE_ENV: t.Union([
          t.Literal('development'),
          t.Literal('production'),
          t.Literal('test'),
        ], { default: 'development' }),
        DATABASE_URL: t.String(),
        JWT_SECRET: t.String(),
        REDIS_URL: t.Optional(t.String()),
      }),
    }),
  ],
})
export class AppModule {}

Using ConfigService

import { Injectable } from 'next-js-backend';
import { ConfigService } from 'next-js-backend';

@Injectable()
export class DatabaseService {
  constructor(private config: ConfigService) {}

  connect() {
    const url = this.config.get('DATABASE_URL');
    const port = this.config.get('PORT'); // typed as number
    return connectToDb(url);
  }
}

ConfigService.get(key) returns the value with the TypeBox-inferred type — no manual casting needed.

Type-safe Config

TypeBox ensures:

• Missing required vars → startup error (fail-fast)
• Wrong type → automatic coercion or error
• Default values → applied automatically

.env File

PORT=3000
NODE_ENV=development
DATABASE_URL=postgresql://user:pass@localhost:5432/mydb
JWT_SECRET=super-secret-key

Env Validation

Variables are validated at startup. If DATABASE_URL is missing:

Error: Config validation failed:
  [DATABASE_URL] Required string property is missing

This ensures your app never starts with invalid configuration.