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EJB 3 Developer Guide

EJB 3 Developer Guide

By : Michael Sikora
4.2 (6)
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EJB 3 Developer Guide

EJB 3 Developer Guide

4.2 (6)
By: Michael Sikora

Overview of this book

Table of Contents (18 chapters)
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EJB 3 Developer Guide
Credits
About the Author
About the Reviewers
Preface
1
Annotations and Their Corresponding Packages

Chapter 3. Entities

Entities are classes that need to be persisted, usually in a relational database. In this chapter we cover the following topics:

  • EJB 3 entities

  • Java persistence API

  • Mapping an entity to a database table

  • Metadata defaults

  • Introduction to the entity manager

  • Packaging and deploying entities

  • Generating primary keys

  • Overriding metadata defaults

Introduction

Entities are classes that need to be persisted; their state is stored outside the application, typically in a relational database. Unlike session beans, entities do not have business logic other than validation. As well as storing such entities, we want to query, update, and delete them.

The EJB 3 specification recognizes that many applications have the above persistence needs without requiring the services (security, transactions) of an application server EJB container. Consequently the persistence aspects of EJB 3 have been packaged as a separate specification—the Java Persistence API (JPA). JPA does not assume we...

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