Java Reference
In-Depth Information
Interacting with Databases
through the Java
Persistence API
The
Java Persistence API
(
JPA
) is an
object-relational mapping
(
ORM
) API. ORM
tools help us to automate the mapping of Java objects to relational database tables.
Earlier versions of J2EE used Entity Beans as the standard approach for ORM. Entity
Beans attempted to always keep the data in memory synchronized with the database
data, a good idea in theory, however, in practice this feature resulted in poorly
performing applications.
Several ORM APIs were developed to overcome the limitations of Entity Beans, such
as Hibernate, iBatis, Cayenne, and TopLink, among others.
Java EE 5 deprecated Entity Beans in favor of JPA. JPA took ideas from several ORM
tools and incorporated them in the standard. As we will see in this chapter, NetBeans
has several features that make development with JPA a breeze.
The following topics will be covered in this chapter:
• Creating our first JPA entity
• Interacting with JPA entities using EntityManager
• Generating JPA entities from an existing database schema
• JPA named queries and
Java Persistence Query Language
(
JPQL
)
• Entity relationships
• Generating complete JSF applications from JPA entities
