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  • Book Overview & Buying EJB 3 Developer Guide
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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

Generating Primary Keys


Up to now we have relied on the application to set an entity's primary key by supplying a primary key identifier as a parameter. However, we may want to relieve the application of this responsibility and use automatically generated keys. JPA provides the Table, Sequence, Auto, and Identity strategies for generating primary keys.

Table Strategy

With this strategy the persistence engine uses a relational database table from which the keys are generated. This strategy has the advantage of portability; we can use it with any relational database. Here is an example of how we would specify a table generation strategy for the id attribute of the Customer entity:

@TableGenerator(name="CUST_SEQ",
table="SEQUENCE_TABLE",
pkColumnName="SEQUENCE_NAME",
valueColumnName="SEQUENCE_COUNT")
@Id
@GeneratedValue(strategy=GenerationType.TABLE,
generator="CUST_SEQ")
public int getId() { return id; }

First we use the @TableGenerator annotation to specify the table used for key generation...

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Tech Concepts
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Programming languages
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EJB 3 Developer Guide
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