HTTP Interceptors

4.0.0 uses request/reply functions and native Fastify hooks. Express next() middleware is no longer supported.

import 'reflect-metadata';
import {Rest, Get, Interceptors, type FastifyInterceptor} from '@heronjs/express';
 
const requestId: FastifyInterceptor = (request, reply) => {
  reply.header('x-request-id', request.id);
};
 
@Rest('/health')
@Interceptors([requestId])
export class HealthController {
  @Get({uri: '/'})
  health() {
    return {ok: true};
  }
}

@Interceptors applies at class or method level. Register the controller in @Module({controllers: [...]}). Interceptors support values, Promises and Observables; finite interceptor execution is awaited.

For global behavior, pass options.interceptors to app.listen(). options.globalError accepts a FastifyErrorInterceptor with (error, request, reply) arguments. Return a sanitized response rather than exposing internal exception details.

Use options.hooks(instance) and instance.addHook(...) for native Fastify lifecycle hooks. Third-party integrations belong in Fastify plugins. See configuration and migration.