@node-ts/bus-core

@node-ts/bus-core

The core messaging framework. This package provides an in-memory queue and persistence by default, but is designed to be used with other @node-ts/bus-* packages that provide compatibility with other transports (SQS, RabbitMQ, Azure Queues) and persistence technologies (PostgreSQL, SQL Server, Oracle).

Installation

Download and install the packages:

npm i inversify @node-ts/bus-core --save

Load BusModule into your application's inversify container:

// application-container.ts

import { Container } from 'inversify'
import { BusModule } from '@node-ts/bus-core'

export class ApplicationContainer extends Container {
  constructor () {
    this.load(new BusModule())
  }
}

Register a message handler

Messages are handled by defining and registring a handler class. Each time a message is received by the application, it will be dispatched to each of the registered handlers.

Define the handler:

// send-email-handler.ts

import { injectable } from 'inversify'
import { HandlesMessage, Handler } from '@node-ts/bus-core'
import { SendEmail } from 'my-corporation/commands'
import { SERVICE_SYMBOLS, EmailService } from '../services'

@HandlesMessage(SendEmail)
export class SendEmailHandler implements Handler<SendEmail> {
  
  constructor (
    @inject(SERVICE_SYMBOLS.EmailService) private readonly emailService: EmailService
  ) {
  }

  async handle (sendEmailCommand: SendEmail): Promise<void> {
    await this.emailService.send(
      sendEmailCommand.to,
      sendEmailCommand.title,
      sendEmailCommand.body
    )
  }
}

Register the handler:

// application.ts

import { inject, injectable } from 'inversify'
import { BUS_SYMBOLS, ApplicationBootstrap, Bus } from '@node-ts/bus-core'

@injectable()
export class Application {

  constructor (
    @inject(BUS_SYMBOLS.ApplicationBootstrap) private readonly applicationBootstrap: ApplicationBootstrap,
    @inject(BUS_SYMBOLS.Bus) private readonly bus: Bus
  ) {
  }

  async initialize (): Promise<void> {
    this.applicationBootstrap.registerHandler(SendEmailHandler)

    // Starts the receive loop on the bus to pull messages from the queue and dispatch to handlers
    await this.applicationBootstrap.initialize()
  }

  async stop (): Promise<void> {
    // Stops the queue polling mechanism so the app shuts down cleanly
    await this.bus.stop()
  }
}