3 Domain models and metadata

This chapter covers

  • Introducing the CaveatEmptor example application
  • Implementing the domain model
  • Examining object/relational mapping metadata options

The “Hello World” example in the previous chapter introduced you to Hibernate, Spring Data, and JPA, but it isn’t useful for understanding the requirements of real-world applications with complex data models. For the rest of the book, we’ll use a much more sophisticated example application—CaveatEmptor, an online auction system—to demonstrate JPA, Hibernate, and later Spring Data. (Caveat emptor means “Let the buyer beware.”)

Major new features in JPA 2

A JPA persistence provider now integrates automatically with a Bean Validation provider. When data is stored, the provider automatically validates constraints on persistent classes.

The Metamodel API has also been added. You can obtain the names, properties, and mapping metadata of the classes in a persistence unit.

3.1 The example CaveatEmptor application

3.1.1 A layered architecture

3.1.2 Analyzing the business domain

3.1.3 The CaveatEmptor domain model

3.2 Implementing the domain model

3.2.1 Addressing leakage of concerns

3.2.2 Transparent and automated persistence

3.2.3 Writing persistence-capable classes

3.2.4 Implementing POJO associations

3.3 Domain model metadata

3.3.1 Annotation-based metadata

Summary

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