This is a lightning presentation given by Scott Rabon, a member of my development team. He presents a high level overview of the JPA based on his first exposure to it.

1. Java Persistence API (JPA)
A Brief Overview
By Scott Rabon

2. We have come a long way
• Java
application
persistence
history
– JDBC
– EJB Entity
Beans
1

3. Industry answered the call
• Proprietary
persistence products
were introduced
– JBoss Hibernate
– Oracle Top Link
2

4. Why Another Standard
• Standard goes
deeper than a product
• Can be implemented
by different vendors
• Developers code to
interface, not
implementation
3

5. A Standard Is Born
JSR 220 – EJB 3.0
Specification
Java Persistence
API part of EJB 3.0
Specification
4

6. JPA Fun Facts
• JSR 220 formed May
2003
• Released May 2006
• Expert group
consisted of industry
ORM developers
5

7. JPA – Designed for Ease of Use
• Main goal of design
team
• Elegant, powerful and
flexible
• Easy to learn
6

8. Aspects: POJO Persistence
• Objects are POJO’s
• Mapping is metadata
driven
• External XML or
annotation based
7

9. Aspects: Non Intrusiveness
• API does not intrude
on objects
• API exists as a
separate layer from
persistent objects
• Objects are
“unaware” of the API
8

10. Aspects: Object Queries
• Query across entities
and relationships
• Expressed in Java
Persistence Query
Language (JPQL)
• Uses a schema
abstraction
9

11. Aspects: Mobile Entities
• Detachment Model
• Move entities
between JVM’s
• Can change state
anywhere along the
way
• Reattach upon return
10

12. Aspects: Simple Configuration
• Java SE 5
Annotations
• XML
• Heavy use of defaults
11

13. Aspects: Integration and Testability
• Challenge: Testing on
an app server
• API works outside
application server
– Two tier apps
– Unit tests and
automated testing
frameworks
12

14. Entities
Not same as entity
beans
13

15. Entity Characteristics -
Persistability
• Entities must be persistable
• State can be represented in
a data store
• Entities can be manipulated
without having persistent
repercussions – app must
use API
14

16. Entity Characteristics - Identity
• Key that uniquely
identifies an instance
• Persistent identity
• Equivalent to primary
key
15

17. Entity Characteristics -
Transactionality
• Adds, updates and
deletes normally
occur in a transaction
• Changes succeed or
fail atomically
• In memory entities
16

18. Entity Characteristics - Granularity
• Not primitives,
wrappers, built-in
objects
• Are business domain
objects that mean
something
• Should be fairly
lightweight objects
17

19. Entity Manager
• Interface encapsulating
most persistence
functionality
• Set of managed
instances is named
persistence context
18

20. Queries
• Use JPQL syntax
• Can be defined
statically (named) or
dynamically
• Dynamic queries
supply query criteria
19

21. JPA’s future - Independence
• Break free from the
EJB specification
• Will get it’s own JSR
for future evolution
20

22. The End
5 minutes of question time
starts now!

23. Questions
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27. Questions
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28. Questions
TIME IS UP!