13.6. Summary

This chapter presented various best practices applicable when working with JDO.

The section called “Data Modeling” covered best practices for modeling and coding the domain model of persistent classes. Advanced applications may wish to fine tune usage of certain JDO features and, for example, store some fields embedded in others, use arrays for small collections of fixed size multi-value fields, reference to non-persistence-capable classes, and so on. For the other 80 percent of all applications, however, the usage guidelines presented should prove useful.

A brief discussion on JDO and the Servlet API showed how transparent persistent could be used directly from within Web applications. Some similarities to concepts seen in the EJB chapter (regarding storing and retrieving by object identities) were mentioned.

The section called “Using XML as a Data Exchange Format” described how persistent objects could be stored and read from the XML format. This can be useful for data exchange or migration purposes.

In the section called “Validation,” ways to enforce data integrity were explored.