Services in the application logic layer have the following features:
The service requester factory is responsible for creating new service requesters. The service requester factory creates service requesters based on a service requester's resource bundle file, which defines the requester ID, the service type, the invocation type, and the service ID of the service requester.
The service requester factory also stores created service requesters in the cache of the JVM so that when a toolkit application subsequently asks for the same requester, the service requester factory does not need to create the requester again.
Service requesters are the facade of the services. Service requesters enable service invokers (for example, the business processes) to access services by passing the request from the invokers to the service container. Service requesters must be on the same server as the service invokers.
Service holders can be deployed as Web Services or EJBs that function as the interface of service objects. If you want to have your services deployed on more than one servers, deploy a service holder on each of those servers. Service holders do the following:
Service objects are the entity that process the service requests. For example, service objects of the database service do the interactions with databases. Each service object is associated with a service type that indicates the kind of service that service object offers. Note that you must deploy service objects on servers that have a service holder installed.