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Java™ Data Objects by Robin M. Roos

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5.5. Type restrictions for persistent fields

The XML Document Type Definition (DTD) for the persistence descriptor allows individual fields of a persistence-capable class to be marked as persis tent, transactional, or none. Fields that are persistent are by default transactional as well.

5.5.1. Non-persistent non-transactional fields

For non-persistent non-transactional fields there are no type restrictions, and such fields in a persistence-capable class may be of any allowable Java type. JDO does not manage the values of such fields in any way.

5.5.2. Transactional non-persistent fields

For non-persistent but transactional fields, there are once again no type restrictions. JDO will manage these fields’ values only in so far as they are cached ...

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