Introduction

The NextGen application—like most—requires storing and retrieving information in a persistent storage mechanism, such as a relational database (RDB). This chapter explores the design of a framework for storing persistent objects.

It is usually better to get or buy than build one of these, either as a standalone product or as part of container-managed persistence for entity beans if using EJBs and other Java technologies. Building an industrial-strength O-R persistence service can consume person-years of effort, and there are subtle issues requiring specialized expertise. Furthermore, technologies such as those based on the Java Data Objects (JDO) specification offer partial solutions.

Therefore, the intention is not to show an industrial-strength framework or suggest ignoring technologies like JDO, but rather to use a persistence framework as a vehicle for explaining general framework design with patterns, because it makes an especially good case study. It is also another demonstration of using the UML to communicate a software design.