The JDO PersistenceManager is the primary interface for JDO-aware application components. It is the factory for the query interface and contains methods for managing the life cycle of persistent instances.
The JDO PersistenceManager interface is designed to support a variety of environments and data sources, from small footprint, real-time embedded systems to large enterprise application servers. It might be a layer on top of a standard Connector implementation such as JDBC or JMS, or itself include connection management and distributed transaction support.
J2EE Connector support is optional. If it is not supported by a JDO implementation, then a constructor for the JDO PersistenceManager or PersistenceManagerFactory is required.
There are three primary environments in which the JDO PersistenceManager is designed to work:
- Non-managed (non-application server): minimum function, single transaction, single JDO PersistenceManager where compactness is important.
- Non-managed but where extended features are desired: multiple PersistenceManager instances may support multiple data sources, XA coordinated transactions, or nested transactions.
- Managed: where the full range of capabilities of an application server is required.
A JDO PersistenceManager instance supports one transaction at a time and uses one connection to the underlying data source at a time. The JDO PersistenceManager instance might use multiple transactions serially, and might use multiple connections serially. Therefore, to support multiple concurrent connection-oriented data sources in an application, multiple JDO PersistenceManager instances are required.
More on the general topic: Java Data Objects (JDO)
Author: Douglas K Barry
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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.