2.4. Rolling Your Own Persistence Mapping Layer
The preceding sections explored some object-relational specific mapping issues. The following section looks into some topics that are not strictly O/R-related, but apply to any persistence framework that maps a Java object from and to an external datastore, be it relational, an object database, XML repositories, or any other imaginable data store.
While again such issues are addressed by existing products and do not need to be a source of concern for application-level developers, an understanding, or at least awareness of it may be of interest.
Furthermore, such issues have to be addressed if you want to realize your own JDO-like persistence layer with good performance characteristics. This section ...