View source for EJB high level

* Separates transaction and security metadata from bean
* Provides transaction management, state management, resource pooling, security

* if not using security or transactions question if you need EJB

= EJB3 =
* No longer have to lookup home and do create. Bean created automatically when looked up.
* Tend to be called "Entity" in EJB 3 and "Entity Bean" in EJB 2.0

== JPA ==
Defines:
* Creation of ORM (Object-Relational Mapping) metadata
* Entity Manager API - API for CRUD - persistence operations
* JPQL (Java persistence query language) - searching & retrieving

Designed to also exist outside application server

== Entity Manager ==
* Reads ORM metadata
* Persists data - performs CRUD operations
* Handles life-cycle - performance tuning - cache, transaction management

== JPQL ==
Supports:
* inner joins
* outer joins
* bulk updates
* delete
* sub queries
* Does not support full sql
Also supports native queries - exam doesn't consider this as full sql

== Terminology ==
=== EJB 3 ===
* Remote business interface - the @remote interface

* Supports annotations and deployment descriptors
** deployment descriptor overrides
*** So can deploy in different environments without changing code

* No longer have to implement lifecycle callbacks
** can put lifecycle callbacks in a separate class
  public class FooListener{
    @PrePassivate public void doPrePassiveStuff() {
       ....
    }
  }

  @CallbackListener FooListener
  @stateful
  public class FooBean{

=== EJB 2 ===
* Remote home interface - factory for creating bean
* Component interface - clients view - interface of the bean
** remote component interface - remote proxy for accessing the bean
** local component interface (also known as local client)
* Business interface - interface implemented by the remote component interface and the bean

= EJB 2 =
* Home   - javax.ejb.EJBHome - factory pattern to create instance of EJB
* Remove - javax.ejb.EJBObject - proxy for accessing the bean
* Bean  
*# javax.ejb.Session - information to persist
*## Stateless - Do not hold conversational state - no guarentee the client will call same bean
*## Stateful  - Can hold state - will be the same bean across client calls e.g. shopping basket
*##* also use to for workflow
*# javax.ejb.Entity  - the implementation containing business logic