NestApplication

Kind: Class

Source: packages/core/nest-application.ts

Part of: Core

NestApplication is the core runtime class behind a Nest HTTP application. It coordinates HTTP server creation, module registration, WebSocket integration, parser middleware, and application lifecycle initialization. Applications are typically created through NestFactory, which configures and returns a NestApplication instance.

Extends: NestApplicationContext

Implements: INestApplication

Methods

Properties

Where it refuses work

• NestApplication stops the work with an early return when !this.appOptions || !this.appOptions.cors.
• NestApplication stops the work with an early return when !passCustomOptions.
• NestApplication stops the work with an early return when !this.socketModule.
• NestApplication stops the work with an early return when this.isInitialized.
• NestApplication stops the work with an early return when originalCallbackArgs[0] instanceof Error.
• NestApplication stops the work with an early return when platform() === 'win32'.

Diagram

mermaid
graph LR
  A[NestFactory.create()] --> B[NestApplication]
  B --> C[createServer()]
  B --> D[registerModules()]
  B --> E[registerWsModule()]
  B --> F[registerParserMiddleware()]
  B --> G[init()]
  G --> H[HTTP Adapter]
  H --> I[Underlying HTTP Server]
  B --> J[dispose()]

Usage

ts
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

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

  // Initialize registered modules, middleware, and adapters.
  await app.init();

  const httpAdapter = app.getHttpAdapter();
  const server = app.getUnderlyingHttpServer();

  console.log(`Using adapter: ${httpAdapter.getType()}`);
  console.log(`Server available: ${Boolean(server)}`);

  await app.listen(3000);

  process.on('SIGTERM', async () => {
    await app.close();
    await app.dispose();
  });
}

bootstrap();

AI Coding Instructions

• Create application instances through NestFactory.create() rather than constructing NestApplication directly.
• Preserve the initialization order: register modules and infrastructure before calling init().
• Use getHttpAdapter() for adapter-specific integrations; avoid assuming Express or Fastify APIs are always available.
• Use getUnderlyingHttpServer() only when direct access to the native HTTP server is required.
• Ensure shutdown paths clean up resources through the application lifecycle, including disposal when appropriate.

Relationships

• IMPORTS → CanActivate
• IMPORTS → ExceptionFilter
• IMPORTS → HttpServer
• IMPORTS → INestApplication
• IMPORTS → INestMicroservice
• IMPORTS → NestHybridApplicationOptions
• IMPORTS → NestInterceptor
• IMPORTS → PipeTransform
• IMPORTS → VersioningOptions
• IMPORTS → VersioningType
• IMPORTS → WebSocketAdapter
• IMPORTS → GlobalPrefixOptions
• IMPORTS → NestApplicationOptions
• IMPORTS → Logger
• IMPORTS → loadPackage
• IMPORTS → addLeadingSlash
• IMPORTS → isFunction
• IMPORTS → isObject
• IMPORTS → isString
• IMPORTS → SocketModule
• IMPORTS → MicroservicesModule
• IMPORTS → -nestjs-microservices

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)

• TestingModule — packages/testing/testing-module.ts:26
• BaseWsInstance — packages/websockets/adapters/ws-adapter.ts:8