When you use a transparent persistence interface like JDO with an object database, there is no need for data conversion (or mapping) from tables to objects and back. Both the Enterprise Java Beans (EJBs) and the database use the same object model. This is illustrated in the diagram where it indicates that no data conversion is needed.
If you use a relational database as part of an EJB accelerator, there will be data conversion. The location of that data conversion will depend on the interface you use:
For more information on EJB accelerators and application servers, see When to Use EJB Accelerators with Java Application Servers.
Context for EJB Accelerator Data Conversion
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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.