Java Reference
In-Depth Information
Data persistence meets the standard
The arrival of an Enterprise Java Persistence standard based on the
Plain Old Java Object
(
POJO
) development model fills a substantial gap in the Java EE platform. The previous
attempt (the EJB 2.x specification) missed the mark and created a stereotype of EJB entity
beans that was awkward to develop and too heavy for many applications. Therefore, it nev-
er achieved widespread adoption or general approval in many sectors of the industry.
Software developers knew what they wanted, but many could not find it in the existing
standards, so they decided to look elsewhere. What they found was lightweight persistence
frameworks, both in the commercial and open source domains.
In contrast to EJB 2.x entity beans, the EJB 3.0
Java Persistence API
(
JPA
) is a metadata
driven POJO technology, that is, to save the data held in Java objects in a database, our ob-
jects are not required to implement an interface, extend a class, or fit into a framework pat-
tern.
Another key feature of JPA is the query language called the
Java Persistence Query Lan-
guage
(
JPQL
), which gives you a way to define the queries in a portable way, independent
of the particular database you use in an enterprise environment. JPA queries resemble SQL
queries by syntax but operate against entity objects rather than directly with database
tables.
