If the data in your database is complex or the mapping from the relational model to the Java object model is complex, it is best to use JDO with Java application servers instead of JDBC or SQLJ. This would mean that the mapping can be placed in one location outside of your application or application server as opposed to mapping data in multiple locations. See JDBC Data Conversion and SQLJ Data Conversion. Having to map data in only one location simplifies both development and maintenance.
If you have new data and do not have an existing database that requires data mapping, take a look at EJB accelerators.
For more information on JDO issues related to data mapping, see JDO Data Conversion.
Also, if you are not familiar with the concept of complex data, see complex data.
Context for When to Use JDO with Java Application Servers
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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.