Summary


Jini services are manifested as Java objects that expose an interface conforming to the Jini specification. This is in contrast to JXTA and other P2P protocols that maintain programming language-neutrality.

Jini services advertise their operations by registering an object with a Jini-compliant lookup service. Service registration is at the core of building the Jini network community.

There are three infrastructure services that are required somewhere on your Jini network. They are as follows:

  • An HTTP server that supports dynamic downloading of code

  • The Remote Method Invocation daemon (rmid) that provides the distributed remote object lookup and activation mechanism

  • The Jini Lookup Service that provides the service registry and the service lookup capabilities on the Jini network

The Sun-supplied Jini services rely heavily on the Remote Method Invocation (RMI) framework. Understanding RMI is critical to understanding Jini. RMI provides P2P systems with the capability to exchange objects, not just messages or XML.

The discovery and join protocols are protocols that enable services to discover, become part of, and advertise supplied services to other members of the Jini community.

The discovery protocol requires support for multicast or restricted-scope broadcast (such as UDP), along with support for reliable unicast delivery in the transport layer (such as TCP). The discovery protocol makes use of the Java platform's object serialization capabilities to exchange information in a platform-independent manner.

The join protocol makes use of the discovery protocol to provide a standard sequence of steps that services should perform when they are starting up and registering themselves with a LUS. The join protocol is used to register a service and advertise its functionality in all lookup services of interest.

To help simplify the process of developing clients and services for the Jini environment, several helper services have been defined. The Jini specifications define two categories of helper entities: helper utilities and helper services. These utilities and services provide a basis for building applications that demonstrate desirable behavior in a Jini community.

One of the most important services for Jini-P2P is the JavaSpaces service. JavaSpaces is a Jini service that supports distributed persistence and the design of distributed algorithms. We will look at this service in more detail in the next chapter.



JavaT P2P Unleashed
JavaT P2P Unleashed
ISBN: N/A
EAN: N/A
Year: 2002
Pages: 209

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