Integrations

The domain and the application import no framework: every class receives its dependencies in its constructor, typed with abstract classes. Only the composition root of each bounded context knows how to build them, by hand or with a container.

Without a container

With Express, Fastify, Hono or plain Node.js, the composition root builds everything with new:

src/ordering/ordering.module.ts

export class OrderingModule {
	readonly placeOrder: PlaceOrderHandler;

	constructor(db: Pool) {
		this.placeOrder = new PlaceOrderHandler(new PgOrders(db), new SystemClock(), new RandomIdGenerator());
	}
}

Routes, consumers and jobs then call handle and map the Result: see Command handlers.

With a container

The abstract classes of your ports and repositories are the injection tokens: register each adapter under its port. See NestJS.

See also

• Project layout: composition root
• layer-direction, which keeps frameworks out of the application