3 Domain models and metadata

 

This chapter covers

  • Discovering 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 and Spring Data; certainly, it isn’t useful for understanding the requirements of real-world applications with complex data models. For the rest of the book, we use a much more sophisticated example application—CaveatEmptor, an online auction system—to demonstrate Jakarta Persistence, 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 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

3.3.2 Applying constraints to Java objects

3.3.3 Externalizing metadata with XML files

3.3.4 Accessing metadata at runtime

3.4 Summary

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