Summary

This chapter introduces JDO's persistence service and defines much of the vocabulary needed to discuss it. As often happens when a paradigm changes, new terms are required to describe the new concepts and their interrelationships. This chapter uses, so far as possible, old and familiar concepts to define the new terms.

JDO is a paradigm shift for application programmers who are used to working with a datastore service. JDO encapsulates and removes from the application all of the work involved in interacting with a datastore service. In place of the datastore service for information, JDO provides a persistence service for objects. This service ensures that some aspects of persistence are taken care of transparently without requiring the application to make explicit requests.

Although JDO hides some persistence services, it also exposes the aspects of persistence that the application must control. Queries and transactions are among the most important of JDO's explicit services. The next chapter describes how to construct and execute a query using JDO.