RouterExplorer

Kind: Class

Source: packages/core/router/router-explorer.ts

Part of: Core

RouterExplorer discovers controller route metadata and binds route handlers to the configured HTTP adapter. It creates proxied handlers with exception handling and request-scoped dependency resolution, making it a core part of the framework’s controller-to-router integration.

Methods

Where it refuses work

• RouterExplorer stops the work with UnknownRequestMappingException when isUndefined(path).
• RouterExplorer stops the work with InternalServerErrorException when !next.
• RouterExplorer stops the work with an early return when Array.isArray(path).
• RouterExplorer stops the work with an early return when !host.

When something fails

• RouterExplorer handles failure in 2 places: it logs it and continues in 1, and lets it reach the caller in 1.

Diagram

mermaid
graph LR
  Controller[Controller instance] --> Metadata[Route metadata]
  Metadata --> RouterExplorer
  RouterExplorer --> Extract[extractRouterPath()]
  Extract --> Apply[applyPathsToRouterProxy()]
  Apply --> Proxy[Router proxy]
  Proxy --> Adapter[HTTP adapter router]
  Adapter --> Handler[Controller handler]

  Handler --> Scoped[createRequestScopedHandler()]
  Scoped --> Injector[Request-scoped injector]

Usage

ts
import { RouterExplorer } from '@nestjs/core/router/router-explorer';

// RouterExplorer is typically created by the framework during application setup.
// This demonstrates how the framework registers a discovered controller wrapper.
routerExplorer.explore(
  controllerWrapper, // InstanceWrapper containing a controller instance
  moduleKey, // Internal module identifier
  httpAdapter, // HttpServer / platform adapter router
  undefined, // Optional host restriction
  {
    modulePath: '/api',
    controllerPath: '/users',
    methodPath: '',
  },
);

// The explorer reads @Controller(), @Get(), @Post(), and related metadata,
// then registers proxied handlers on the HTTP adapter.

AI Coding Instructions

• Preserve the separation between route discovery (extractRouterPath) and route registration (applyPathsToRouterProxy).
• Always register handlers through RouterProxy so framework exception filters and async error handling remain active.
• Use createRequestScopedHandler for request-scoped controllers or dependencies; do not resolve request-scoped providers from the static controller instance.
• Keep route metadata compatible with RoutePathFactory, including module paths, controller paths, method paths, versioning, and host constraints.
• Treat RouterExplorer as framework infrastructure; application code should define routes with controller decorators rather than instantiate this class directly.