Dependency Injection

HeronJS 4.0.0 uses application-local containers and registries. Use the container and registry on the application returned by HeronJS.create(). Decorators record metadata; explicitly declare application components in modules.

import 'reflect-metadata';
import {Inject, injectable, Module} from '@heronjs/common';
import {Rest, Get} from '@heronjs/express';
 
@injectable()
class Greeting {
  message() {
    return 'Hello Heron';
  }
}
 
@Rest('/hello')
class HelloController {
  constructor(@Inject(Greeting) private greeting: Greeting) {}
 
  @Get({uri: '/'})
  hello() {
    return {message: this.greeting.message()};
  }
}
 
@Module({providers: [Greeting], controllers: [HelloController]})
export class AppModule {}

Use imports to compose modules and declare export visibility explicitly. Module traversal uses constructor identity and handles cycles and repeated imports. Importing a decorator does not register global runtime state.

Typed tokens

Constructors and Token<T> preserve the relationship between registration and resolution. String and symbol lookups return unknown and require validation.

import {Token, createContainer} from '@heronjs/common';
 
interface Clock {
  now(): number;
}
const clock = new Token<Clock>('clock');
const container = createContainer();
container.registerInstance(clock, {now: () => Date.now()});
const timestamp: number = container.resolve(clock).now();
await container.dispose();

registerInstance leaves ownership with the caller. Use registerOwnedInstance or onDispose when the container should clean up a resource. Disposal is asynchronous and idempotent and attempts all owned cleanup. Factory-created resources need explicit cleanup registration.

Use the exported GATEKEEPER and GATEKEEPER_RESOLVER token identities for authentication dependencies. Class and method guards both apply; asynchronous requirements and predicates are awaited.

See migration for removed globals, typed metadata and renamed contracts, and worker lifetimes for worker-local containers and job scopes.