GraphQL Quick Start

Install @heronjs/gql@4.0.0 alongside matching core, common and HTTP packages. GraphQL uses graphql-http/lib/use/fastify on the application’s shared HTTP listener.

import 'reflect-metadata';
import {Module} from '@heronjs/common';
import {HeronJS} from '@heronjs/core';
import {GraphQL, Resolver} from '@heronjs/gql';
import {of} from 'rxjs';
 
@GraphQL({typeDefs: '', Query: 'greeting: String!'})
class Queries {
  @Resolver()
  greeting() {
    return of('Hello Heron');
  }
}
 
@Module({graphqls: [Queries]})
class AppModule {}
 
const app = await HeronJS.create({module: AppModule});
await app.listen({port: 3000, host: '127.0.0.1'});
// await app.close() when finished.

Query the default endpoint:

curl http://127.0.0.1:3000/graphql \
  -H 'content-type: application/json' \
  --data '{"query":"{ greeting }"}'

@GraphQL declares the schema module and @Resolver declares its resolver methods. Parameter decorators include @GqlContext(), @GqlInfo(), @GqlParams() and @GqlParent().

Resolver results can be values, Promises or Observables. The first emission supplies the result. Guard evaluation and resilience writes are awaited; unexpected resolver errors are masked at the response boundary. Disposing the extension cancels its active handlers.

See HTTP migration for native request/reply integration and reactive execution for cancellation and empty-result behavior.