Java Reference
In-Depth Information
data integrity. Enterprise beans support transactions, the
mechanisms that manage the concurrent access of shared
objects. The application will have a variety of clients. With
just a few lines of code, remote clients can locate enterprise
beans. These clients can be thin, various, and numerous.
Scalable applications can be building using EJBs.
EJB 3.0 has been split into two parts: the EJB spec and the
JPA spec. EJBs are now known as entities in JEE 5 and later
and are POJOs. JPA (Java Persistence API) is as the name
suggests the persistence part of the API. This is commonly
used in libraries like EclipseLink, Hibernate and Toplink.
Hibernate is the most popular and predates JPA but the
differences aren't so large. JPA is an ORM (object-relational
mapper) for projecting an object model onto a relational
database.
EJB 3 Improvements
• Simplified process of developing ejb reduces significantly
overhead.
• Using Java Language annotations as configuration improves
developer's productivity.
• Specification of programmatic defaults, including for
metadata, reducing the need for the developer to specify
common, expected behaviors and requirements on the EJB
container.
• Encapsulation of environmental dependencies and JNDI
access through the use of annotations, dependency injection
mechanisms, and simple lookup mechanisms.
