NestApplicationContext

Kind: Class

Source: packages/core/nest-application-context.ts

Part of: Core

NestApplicationContext provides a non-HTTP NestJS application runtime for resolving providers, selecting modules, and managing dependency injection. It underpins application contexts created through NestFactory.createApplicationContext(), allowing scripts, CLI tools, workers, and tests to access Nest-managed services without starting a web server.

Extends: AbstractInstanceResolver

Implements: INestApplicationContext

Methods

Properties

Where it refuses work

• NestApplicationContext stops the work with UnknownModuleException when !selectedModule.
• NestApplicationContext stops the work with an early return when this.isInitialized.
• NestApplicationContext stops the work with an early return when receivedSignal.
• NestApplicationContext stops the work with an early return when !this.shutdownCleanupRef.
• NestApplicationContext stops the work with an early return when this._moduleRefsForHooksByDistance.

When something fails

• NestApplicationContext handles failure in 1 place: it logs it and continues in all 1.

Diagram

mermaid
graph LR
  A[NestFactory.createApplicationContext] --> B[NestApplicationContext]
  B --> C[Module Container]
  C --> D[Root Module]
  C --> E[Feature Modules]
  B --> F[get Provider]
  B --> G[resolve Scoped Provider]
  B --> H[select Module Context]
  H --> I[get Provider from Module]

Usage

ts
import { Injectable, Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

@Injectable()
class ReportService {
  generate() {
    return 'Report generated';
  }
}

@Module({
  providers: [ReportService],
  exports: [ReportService],
})
class ReportsModule {}

@Module({
  imports: [ReportsModule],
})
class AppModule {}

async function bootstrap() {
  const app = await NestFactory.createApplicationContext(AppModule);

  // Resolve a singleton provider from the application context.
  const reports = app.get(ReportService);
  console.log(reports.generate());

  // Select a module before resolving providers from its module scope.
  const reportsContext = app.select(ReportsModule);
  const scopedReports = reportsContext.get(ReportService);

  await app.close();
}

bootstrap();

AI Coding Instructions

• Use get() for singleton or static-scope providers; use resolve() when working with request-scoped or transient providers.
• Call select(ModuleClass) before retrieving a provider when module-specific lookup or strict module boundaries are required.
• Prefer injection tokens or provider classes consistently; ensure queried providers are registered and exported when accessed across module boundaries.
• Always close application contexts created for scripts, tests, or workers with await app.close() to release lifecycle resources.
• Do not instantiate NestApplicationContext directly in application code; create it through NestFactory.createApplicationContext().

How it works

NestApplicationContext is a public class that extends AbstractInstanceResolver and implements INestApplicationContext. It represents an application context backed by a NestContainer, with an optionally selected module and a module-navigation scope. [packages/core/nest-application-context.ts:40-46] [packages/core/nest-application-context.ts:68-81]

The constructor stores the container and options, creates an Injector, obtains the container’s ModuleCompiler, and logs a preview-mode warning when appOptions.preview is true. [packages/core/nest-application-context.ts:68-81] Its instance-link registry is created lazily from the container on the first lookup. [packages/core/nest-application-context.ts:61-66]

Relationships

• IMPORTS → INestApplicationContext
• IMPORTS → Logger
• IMPORTS → LoggerService
• IMPORTS → LogLevel
• IMPORTS → ShutdownSignal
• IMPORTS → Abstract
• IMPORTS → DynamicModule
• IMPORTS → GetOrResolveOptions
• IMPORTS → SelectOptions
• IMPORTS → ShutdownHooksOptions
• IMPORTS → Type
• IMPORTS → NestApplicationContextOptions
• IMPORTS → isEmpty

Used by

2 references from 2 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

Imported by (2)

• NestMicroservice — packages/microservices/nest-microservice.ts:35
• TestingModule — packages/testing/testing-module.ts:26