Understanding the Hello Service API code

In this section, we will try to understand the HelloWorld API (hello-lagom-api) service code. This is an API microservice for the HelloWorld system.

It has the GreetingMessage data model, as shown here:

case class GreetingMessage(message: String) 

object GreetingMessage { 
  implicit val format: Format[GreetingMessage] = 
   Json.format[GreetingMessage] 
}

It has a GreetingMessageChanged event, as shown here:

case class GreetingMessageChanged(name: String, message: String) 
 
object GreetingMessageChanged { 
  implicit val format: Format[GreetingMessageChanged] =                                                                      
    Json.format[GreetingMessageChanged] 
} 
 

It has a greetings Topic, as follows:

object HellolagomService  { 
  val TOPIC_NAME = "greetings" 
} 

This topic is used by embedded Lagom's Kafka or explicitly configured Kafka server to exchange information between microservices available in that Lagom Reactive System.

In this example...