Application host ​

Sometimes an injectable or a module needs to reach the running DanetApplication itself, for example to mount a route directly on the underlying Hono router. Danet registers the application in the injector under the public APPLICATION_HOST token, so anything living in the DI container can obtain it without the application being passed around.

This is Danet's analogue of NestJS's HttpAdapterHost: where a NestJS extension module injects the host to access the Express/Fastify adapter, a Danet extension injects APPLICATION_HOST to access the application and its Hono instance (app.router). This is what allows forRoot-style extension modules to mount their own endpoints.

Injecting the application ​

Any injectable can receive the running application through constructor injection with @Inject(APPLICATION_HOST):

import {
  APPLICATION_HOST,
  DanetApplication,
  Inject,
  Injectable,
} from 'jsr:@danet/core';

@Injectable()
export class AppInfoService {
  constructor(
    @Inject(APPLICATION_HOST) private app: DanetApplication,
  ) {}

  routes() {
    return this.app.router.routes;
  }
}

Mounting a route from a module hook ​

Module classes are constructed with plain new, so they do not get constructor injection. Inside a lifecycle hook such as onAppBootstrap, read the token from the exported injector instead:

import {
  APPLICATION_HOST,
  DanetApplication,
  injector,
  Module,
} from 'jsr:@danet/core';
import { OnAppBootstrap } from 'jsr:@danet/core/hook';

@Module({})
export class MetricsModule implements OnAppBootstrap {
  onAppBootstrap() {
    const app = injector.get<DanetApplication>(APPLICATION_HOST);
    app.router.get('/metrics', (c) => c.text('up'));
  }
}

Import MetricsModule in your root module and /metrics responds as soon as the application listens.