Defining a Singleton Object Type in Interface Style

Defining a singleton object type is a special case of defining an object type. The difference is that a singleton object type does not require a provider. Alternatively, we might say that its unique instance is its own provider.

1. Define a class that models the managed object type. Your class must implement the interface SingletonTeaObject. For example, when modeling a car, we could define a singleton class to represent the engine.

   public class CarEngine implements SingletonTeaObject {
   
       public String getName() {
           // Return the name of the engine instance;
           return "Engine";
       }
   
       public String getDescription() {
           // Return the description of the engine instance;
           return "Car Engine";
       }
   
       public String getKey() {
           // Return the key that corresponds to the engine instance;
           // for example, "Engine"
       }
   
         // These methods give the singleton functionality 
         // that would otherwise be in the provider.
   
       public String getTypeName() {
           // Return the name of the engine object type.
           return "Engine";
       }
   
       public String getTypeDescription() {
           // Return the description of the engine object type.
           return "Car Engine";
       }
   
       public TeaConcept getConcept() {
           // Return the concept type of the driver.
           // In our model, it's a process that steers the car.
           return TeaConcept.RESOURCE;
       }
   
   }

2. Register the singleton instance of the class.

   CarAgentServer server = ...
   // Register other instances, including the top-level object type.
   CarEngine myCarEngine = new CarEngine;
   server.registerInstance(myCarEngine);
    ...
   server.start();

   Notice that instead of registering the provider, we register the unique instance of the engine class.