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
  1. javax.ejb.Session - information to persist
     1. Stateless - Do not hold conversational state - no guarentee the client will call same bean
     2. Stateful - Can hold state - will be the same bean across client calls e.g. shopping basket
        • also use to for workflow
  2. javax.ejb.Entity - the implementation containing business logic