EM.1. Introduction

The The Jini Technology Core Platform Specification, “Distributed Events” states the ability to interpose third-party objects, or “agents,” into an event notification chain as one of its design goals. This specification also describes a notification mailbox object, which stores and forwards event notifications on behalf of other objects, as an example of a useful third-party agent. These mailbox objects can be particularly helpful for objects that need more control over how and when they receive event notifications.

For example, it would be impossible to send event notifications to a transient entity that has detached itself from a system of Jini technology-enabled services and/or devices (Jini system). In such a situation an entity could employ the services of an event mailbox to store event notifications on its behalf before leaving the system. Upon rejoining the Jini system, the entity could then contact the event mailbox to retrieve any collected events that it would otherwise have missed. Similarly, an entity that wishes to deactivate could use an event mailbox to collect event notifications on its behalf while dormant.

Like other Jini technology-enabled services (Jini services), the event mailbox service will grant its services only for a limited period of time without an active expression of continuing interest. Therefore, event mailbox clients still need to renew their leases if they intend to maintain the mailbox’s services beyond the initially granted lease period. Any resources (for example, remote objects or storage space) associated with a particular client can be freed once the client’s lease has expired or been cancelled. In the previous usage scenarios, it might also benefit a transient or deactivatable entity to employ the services of a lease renewal service (see the Jini Lease Renewal Service Specification) to help mitigate the issue of lease maintenance.

The remainder of this specification defines the requirements, interfaces, and protocols of the event mailbox service.

EM.1.1. Goals and Requirements

The requirements of the set of interfaces specified in this document are:

• To define a service that is capable of storing event notifications on behalf of its clients and capable of delivering stored event notifications to those clients upon request

• To provide this service in such a way that it can be used by entities that are temporarily unable or unwilling to receive event notifications

• To provide a service that complies with the policies embodied in the Jini technology programming model

The goals of this specification are:

• To describe the event mailbox service

• To provide guidance in the use and deployment of the event mailbox service

EM.1.2. Other Types

The types defined in the specification of the event mailbox service are in the net.jini.event package. This specification assumes knowledge of The Jini Technology Core Platform Specification, “Distributed Events” and The Jini Technology Core Platform Specification, “Distributed Leasing”. The following object types may be referenced in this chapter. Whenever referenced, these object types will be referenced in unqualified form:

java.rmi.NoSuchObjectException 
java.rmi.RemoteException 
net.jini.core.event.RemoteEvent 
net.jini.core.event.RemoteEventListener 
net.jini.core.lease.Lease 
net.jini.core.lease.LeaseDeniedException