Table of Contents

Implementation Vs Definition

In HexArc, a service can be implemented and/or defined.

By implementation of a service, we mean the implementation of the components of the service.

While, by definition of a service, we mean the configuration of a particular instance of a service, including its declared components and their configuration.

Note: HexArc encourages the separation between the implementation and the definition of a service, so that the components of the service could be reused in other contexts (e.g. the services modelling a lamp, a dimmable lamp and a colored lamp may share the same components that enables the devices to be switched on or off…).

Implementing a service

In HexArc, a service is made of a set of loosely-coupled components, namely Ports, Adapters and models (i.e. the implementations of the Ports).

The components of a service must implement a init method, which initializes the component. The init method will be called when the service is deployed, providing the proper execution context to every component.

Most notably, the execution context of a service component may contain:

  • vertx: the Vertx instance where the service is running;
  • log: a Logger specific to that component;
  • api: the Port exposed by that component, if the component is an Adapter.

Such context is also available outside the init method, but it cannot be safely accessed before the component initialization.

Example 

import io.github.jahrim.hexarc.architecture.vertx.core.components.*
import io.vertx.core.Future

/** Service implementation. */
object ColoredLampService:

  /** Ports. */
  trait LampSwitchPort extends Port:
    def switch(on: Boolean): Future[Unit]
    def isOn: Future[Boolean]

  trait LampColorPort extends Port:
    def changeColor(color: String): Future[Unit]
    def color: Future[String]

  /** Business logic. */
  class ColoredLampModel extends LampSwitchPort with LampColorPort:
    override def init(context: PortContext): Unit = ???
    override def switch(on: Boolean): Future[Unit] = ???
    override def isOn: Future[Boolean] = ???
    override def changeColor(color: String): Future[Unit] = ???
    override def color: Future[String] = ???

  /** Adapters. */
  class LampSwitchHttpAdapter extends Adapter[LampSwitchPort]:
    override def init(context: AdapterContext[LampSwitchPort]): Unit = ???

  class LampSwitchMqttAdapter extends Adapter[LampSwitchPort]:
    override def init(context: AdapterContext[LampSwitchPort]): Unit = ???

  class LampColorHttpAdapter extends Adapter[LampColorPort]:
    override def init(context: AdapterContext[LampColorPort]): Unit = ???

  class LampColorMqttAdapter extends Adapter[LampColorPort]:
    override def init(context: AdapterContext[LampColorPort]): Unit = ???

Full example here.