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What is meant by persistence?
Question: What is meant by persistence
Answer: Persistence indicates that a
collection of data remains intact even if its source is no longer attached to
the network or even more - Java program is not running.
The objects, in JavaSpaces for example, remain available to other users even if
the source has temporarily disconnected from the network. This feature is
critical to keep distributed systems highly available.
In Java by persistence is meant that an object’s lifetime is
not determined by whether a program is executing. In between
invocations of the program the object lives.
The simple example of persistance: serialize object and write it to disk,
then restore the object when the program is reinvoked. If you need a more
serious persistence mechanism, consider Java Data Objects (JDO) or a tool
like Hibernate (http://hibernate.sourceforge.net). This example is taken
from "Thinking in Java" book.
9 comments | | Score: 0
Posted by jalex on Wednesday, July 09, 2003 (00:00:00) (4448 reads)
How is JavaSpaces technology different from databases?
Question: How is JavaSpaces technology
different from a database?
Answer: JavaSpaces technology
provides a more loosely coupled repository of information than databases. The
identity of a client or a server is no longer relevant; data
packets are treated just like any other object posted to the space
as an anonymous service. Databases require a tremendous amount of overhead in
structured programming, screen design, type matching, and indexing
to achieve their results. Clients post specific questions to the server, and
receive a specific answer.
More importantly, JavaSpaces technology can host more than just data. A space
can find, match and reference objects by both type and value, meaning they can
store objects as information or behavior. This means any object-based program,
device, or user profile can join a JavaSpace system. This capacity greatly
enhances the ability to coordinate different functions and processes in a
Java Space technology is ready for usage product although it is still under
development. One example of Java Space based product here:
This newsletter is based on:
"JAVASPACES: A CRITIICAL ANALYSIS OFF CONCEPTS & TECHNIQUES"
21 comments | | Score: 4
Posted by jalex on Tuesday, July 08, 2003 (00:00:00) (3285 reads)