Processes communicate among each other using these shared objects — by updating the state of the objects as and when needed. An object, when deposited into a space, needs to be registered with an Object Directory in the Object Space. Any processes can then identify the object from the Object Directory , using properties lookup, where the property specifying the criteria for the lookup of the object is its name or some other property which uniquely identifies it.
A process may choose to wait for an object to be placed in the Object Space , if the needed object is not already present.
Objects, when deposited in an Object Space are passive, i. Instead, the accessing process must retrieve it from the Object Space into its local memory, use the service provided by the object, update the state of the object and place it back into the Object Space. This paradigm inherently provides mutual exclusion. Because once an object is accessed, it has to be removed from the Object Space , and is placed back only after it has been released. This means that no other process can access an object while it is being used by one process, thereby ensuring mutual exclusion.
JavaSpaces is a service specification providing a distributed object exchange and coordination mechanism which may or may not be persistent for Java objects. It is used to store the distributed system state and implement distributed algorithms. In a JavaSpace, all communication partners peers communicate and coordinate by sharing state.
JavaSpaces can be used to achieve scalability through parallel processing, it can also be used to provide reliable storage of objects through distributed replication, although this won't survive a total power failure like a disk; it is regarded by many to be reliable as long as the power is reliable. Distribution can also be to remote locations; however, this is rare as JavaSpaces are usually used for low-latency , high-performance applications rather than reliable object caching. The most common software pattern used in JavaSpaces is the Master-Worker pattern.
The Master hands out units of work to the "space", and these are read, processed and written back to the space by the workers. In a typical environment there are several "spaces", several masters and many workers; the workers are usually designed to be generic, i.
JavaSpaces principles patterns, and practice - CERN Document Server
JavaSpaces is part of the Java Jini technology, which on its own has not been a commercial success. JavaSpaces remains a niche technology mostly used in the financial services and telco industries where it continues to maintain a faithful following. The following example shows an application made using JavaSpaces. First, an object to be shared in the Object Space is made.
Such an object is called an Entry in JavaSpace terminology. Here, the Entry is used to encapsulate a service which returns a Hello World! The server which provides this service will create an Object Space , or JavaSpace. The Entry is then written into the JavaSpace.
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The client reads the entry from the JavaSpace and invokes its method to access the service, updating its usage count by doing so. The updated Entry is written back to the JavaSpace. From Wikipedia, the free encyclopedia.
SunWorld , August [15 January ]. Categories : Parallel computing Distributed computing architecture Tree programming languages Java platform.
JavaSpaces™ Principles, Patterns, and Practice by Ken Arnold, Susanne Hupfer, Eric Freeman
Each JavaSpace object is a local object that acts as a proxy to the remote space implementation—it is not a reference to a remote object. As a result, all space operations go through the intermediate proxy and then on to the remote space see Figure 2. To transfer an entry to or from the remote space, the proxy makes use of serialization.
Serialization provides a way to turn an object into a stream of bytes that can be stored in a file or transmitted over a network and later reconstituted Stay ahead with the world's most comprehensive technology and business learning platform.