There are three JDO identity models to allow for different underlying database management systems (DBMSs). The type of JDO identity used is a property of a JDO PersistenceCapable class.
The JDO identity models are:
- Application (primary key) identity. This is the JDO identity type used for data stores in which the value(s) in the instance determine the identity of the object in the data store. (This is commonly used in relational DBMSs)
- Data store identity. This is the JDO identity type used for data stores in which the identity of the data in the data store does not depend on the values in the instance. The implementation guarantees uniqueness for all instances. (This is commonly used in object DBMSs.)
- Non-data store JDO identity. The primary usage for non-data store JDO identity is for log files, history files, and other similar files, where performance is a primary concern.
A JDO implementation is required to support either application (primary key) identity or datastore identity, and may optionally support non-datastore identity.
More on the general topic: Java Data Objects (JDO)
Author: Douglas K Barry
You may use this material for your work or classes. Reprint Policy. Be sure to check the menu at the left for other articles available on this site.
The Savvy Manager's Guide
Douglas K Barry is also the author of a book that explains Web Services, service-oriented architecture, and Cloud Computing in an easy-to-understand, non-technical manner.
Web Services, Service-Oriented Architectures, and Cloud Computing: The Savvy Manager's Guide (Second Edition)
by Douglas K Barry with David Dick
This is a guide for the savvy manager who wants to capitalize on the wave of change that is occurring with Web Services, service-oriented architecture, and—more recently—Cloud Computing. The changes wrought by these technologies will require both a basic grasp of the technologies and an effective way to deal with how these changes will affect the people who build and use the systems in our organizations. This book covers both issues. Managers at all levels of all organizations must be aware of both the changes that we are now seeing and ways to deal with issues created by those changes.