Java Persistence with Hibernate

1.2. The paradigm mismatch

The object/relational paradigm mismatch can be broken into several parts, which we'll examine one at a time. Let's start our exploration with a simple example that is problem free. As we build on it, you'll begin to see the mismatch appear.

Suppose you have to design and implement an online e-commerce application. In this application, you need a class to represent information about a user of the system, and another class to represent information about the user's billing details, as shown in figure 1.1.

In this diagram, you can see that a User has many BillingDetails. You can navigate the relationship between the classes in both directions. The classes representing these entities may be extremely simple:

 public class ...