Because the topic of this book is database interaction, the rest of this chapter focuses on the Model layer of the MVC methodology. We will show you how to design abstract methods that can be used and reused in a variety of applications. We'll also show how to weave persistence into your Model with minimal duplication of code, and—for good measure—speed up access by implementation a caching layer.
The Model contains abstractions of all concrete things used within the application. Therefore, a solid Model is an important foundation for the rest of the application.
Luckily for us, designing a Model for a database-driven application is straightforward. That is because the work of discovering the relevant abstractions in a system is done when the database scheme is created, as we described in Chapter 7.
Usually, each table in the database corresponds to one class in the Model. The fields of the tables correspond to the attributes of the class. Relationships between tables can usually be expressed in the following manner:
If two tables have a one-to-one relationship, their relationship can involve either containment or aggregation , concepts that are familiar to object-oriented programmers. If one contains the other, the contained object should be defined as an attribute of the container class. For instance, if every ISBN corresponds to one and only one title, one of them can be an attribute of the other. If the relationship is one of aggregation, ...