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@InjectService

The PAK-Core harbors the core functionality of the PAK-framework. It enables the creation, fetching and execution of Commands. Every component within the core-module, plays a vital part in PAK. This chapter describes the functionality of the @InjectService annotation.

1. Basics

@InjectService can be used for development inside the PAK-framework. Only Services registered within IServiceProvider, or the `ServiceLoader should be annotated by this annotation. Therefore, Services from these instances can be injected into the Service, using @InjectService, so they can access the Services themselves easily. When used, the annotated field is created, like being passed via a constructor during runtime. Those Services have Services itself, which are injected from the current context.

Be careful, don’t create cyclic injection dependencies (do not inject a Service, which is already using @InjectService), as this will lead to a StackOverflowError!

2. Usage

One example usage of this annotation, would be within CommandRestService. IEndpointClientServiceFactory is injected, by using @InjectService.

Listing 1 shows how to use @InjectService, by injected IEndpointServiceFactory

Listing 1. CommandRestService injecting IEndpointClientServiceFactory, by using @InjectService
public class CommandRestService implements ICommandRestService {

	/**
	 * Injected {@link IEndpointClientServiceFactory}, for creating
	 * {@link IEndpointClientService}, by passing different parameters in the
	 * constructor
	 */
	@InjectService (1)
	private IEndpointClientServiceFactory endpointClientServiceFactory;

	public CommandRestService() {
		// Empty constructor
	}

	@Override
	public IEndpointClientService createEndpointClientServiceFor(final String requesterId) {

		return this.endpointClientServiceFactory.createWithId(requesterId); (2)
	}
}
1 IEndpointServiceFactory is injected, by using @InjectService.
2 Usage of IEndpointClientService as normal variable within CommandRestService.