HTTP adapter

Occasionally, you may want to access the underlying HTTP server, either within the Nest application context or from the outside.

Every native (platform-specific) HTTP server/library (e.g., Express and Fastify) instance is wrapped in an adapter. The adapter is registered as a globally available provider that can be retrieved from the application context, as well as injected into other providers.

Outside application context strategy

To get a reference to the HttpAdapter from outside of the application context, call the getHttpAdapter() method.

@@filename()
const app = await NestFactory.create(AppModule);
const httpAdapter = app.getHttpAdapter();

In-context strategy

To get a reference to the HttpAdapterHost from within the application context, inject it using the same technique as any other existing provider (e.g., using constructor injection).

@@filename()
export class CatsService {
  constructor(private adapterHost: HttpAdapterHost) {}
}
@@switch
@Dependencies(HttpAdapterHost)
export class CatsService {
  constructor(adapterHost) {
    this.adapterHost = adapterHost;
  }
}

info Hint The HttpAdapterHost is imported from the @nestjs/core package.

The HttpAdapterHost is not an actual HttpAdapter. To get the actual HttpAdapter instance, simply access the httpAdapter property.

const adapterHost = app.get(HttpAdapterHost);
const httpAdapter = adapterHost.httpAdapter;

The httpAdapter is the actual instance of the HTTP adapter used by the underlying framework. It is an instance of either ExpressAdapter or FastifyAdapter (both classes extend AbstractHttpAdapter).

The adapter object exposes several useful methods to interact with the HTTP server. However, if you want to access the library instance (e.g., the Express instance) directly, call the getInstance() method.

const instance = httpAdapter.getInstance();