Problems with EJB 2.1

1
Problems with EJB 2.1
2
Deployment Descriptors

• Complex
• Multiple
• Partly vendor dependent
• Lack adequate defaults
• Better graphical tools needed

3
Verbosity

• Need two interfaces to specify one EJB.
• Remote and local interface
• Remote and local home interface
• Must implement special EJB classes.
• Numerous callback methods required.
• Even normally-empty callbacks like ejbPostCreate
  must be specified

4
EJB Query Language

• EJB QL is currently weak.
• Strange object-oriented syntax
• Does not implement full SQL language
• Lacks functions and operations
• Programmers are forced to resort to JDBC and SQL.
• EJB 2.1 lacks vendor-independent
  object-relational mapping tools.

5
Testing

• Entity beans are abstract classes.
• Consequently, they are completely untestable
  outside the context of the container.

6
Whats Coming in EJB 3.0
EJB 3.0 Public Review Draft is on your CD (in
three parts). Proposed Final Review Draft due
to be approved in 2006.
7
Organization of the Specification Documents

• EJB 3.0 Simplified API
• EJB 3.0 Core Contracts and Requirements
• Java Persistence API

8
EJB 3.0 Overview

• Purpose is to reduce complexity of the EJB
  architecture from the enterprise application
  developers point of view.
• Replace deployment descriptors with annotations
  in the source code (like javadoc comments).
• Specify defaults representing the expected
  behaviors (configuration by exceptions).
• Backward compatibility with EJB 2.1 (can mix and
  match).

continued
9
EJB 3.0 Overview
continued

• Use of annotations to simplify JNDI lookup
  mechanisms and environmental dependencies.
• Simplification of enterprise bean types.
• Eliminate need for EJB component interfaces for
  session beans. Use plain old Java objects (POJOs)
  instead.
• Eliminate need for home interfaces for session
  beans.

10
EJB 3.0 Overview
continued

• Simplify entity bean persistence.
• Object-relational persistence API will work with
  Hibernate, TopLink and JDO.
• Eliminate all required interfaces for entities
  written to the new persistence API.
• Enhancement of EJB QL.
• Eliminate the requirement for the implementation
  of callback interfaces.
• Improve ability for testing outside the container

11
Acknowledgement

• The following slides are based on code that was
  kindly provided by Bill Burke, Chief Architect at
  JBoss.
• It will appear in his new O'Reilly book
  "Enterprise JavaBeans (Fifth Edition)".

12
Developing an Entity Bean
package com.titan.domain import
javax.persistence. _at_Entity _at_Table(name"CABIN")
public class Cabin implements
java.io.Serializable private int id
private String name private int deckLevel
private int shipId private int bedCount
_at_Id _at_Column(name"CABIN_ID") public
int getId() return id public void
setId(int pk) id pk
_at_Column(name"CABIN_NAME") public String
getName() return name
Cabin The Bean Class
continued
13
Developing an Entity Bean
continued
_at_Column(name"CABIN_NAME") public String
getName() return name public void
setName(String str) name str
_at_Column(name"CABIN_DECK_LEVEL") public int
getDeckLevel() return deckLevel public void
setDeckLevel(int level) deckLevel level
_at_Column(name"CABIN_SHIP_ID") public int
getShipId() return shipId public void
setShipId(int sid) shipId sid
_at_Column(name"CABIN_BED_COUNT") public int
getBedCount() return bedCount public void
setBedCount(int bed) bedCount bed
14
Developing an Entity Bean

• Annotations are objects, for example
• _at_javax.persistence.Entity specifes a persistent
  entity managed by an EntityManager service.
• _at_javax.persistence.Table specifies the database
  table to map to.
• _at_javax.persistence.Column defines a field in the
  database table
• _at_Id specifies the primary key of a row.
• Setters and getters are no longer abstract
  methods as in EJB 2.1.

required
15
Developing an Entity Bean

• Entity bean is a POJO.
• Does not extend javax.ejb.EJBObject.
• Bean class implements Serializable, therefore
• Entity classes can be used as parameters and
  return values.
• Can be used as data transfer objects between
  client and server.
• Can be persisted in a database.

16
persistence.xml
ltpersistencegt ltpersistence-unitgt
ltnamegttitanlt/namegt ltjta-data-sourcegtjava/Defau
ltDSlt/jta-data-sourcegt lt/persistence-unitgt lt/pe
rsistencegt
17
Developing a Session Bean
package com.titan.travelagent import
javax.ejb.Remote import com.titan.domain.Cabin
_at_Remote public interface TravelAgentRemote
public void createCabin(Cabin cabin) public
Cabin findCabin(int id)
TravelAgentRemote The Remote Interface
18
Developing a Session Bean
package com.titan.travelagent import
javax.ejb.Stateless import javax.persistence.
import com.titan.domain.Cabin
_at_Stateless public class TravelAgentBean
implements TravelAgentRemote
_at_PersistenceContext(unitName"titan") private
EntityManager manager public void
createCabin(Cabin cabin)
manager.persist(cabin) public Cabin
findCabin(int pKey) return
manager.find(Cabin.class, pKey)
TravelAgentBean The Bean Class
19
Developing a Session Bean Annotations

• _at_javax.ejb.Remote as opposed to Local.
• _at_javax.ejb.Stateless as opposed to Stateful.
• _at_javax.persistence.PersistenceContext gives
  access to the EntityManager.

20
CABIN Table in the Database
create table CABIN ( ID int primary key NOT
NULL, SHIP_ID int, BED_COUNT int,
NAME char(30), DECK_LEVEL int )
21
Creating a Client Application
package com.titan.clients import
com.titan.travelagent.TravelAgentRemote import
com.titan.domain.Cabin import
javax.naming. import java.util.Properties impor
t javax.rmi.PortableRemoteObject public class
Client_1 public static void main(String
args) try ontext jndiContext
new InitialContext() // use the jndi
properties file Object ref
jndiContext.lookup (TravelAgentRemote.class.ge
tName()) TravelAgentRemote dao (
TravelAgentRemote)PortableRemoteObject.na
rrow (ref,TravelAgentRemote.class)
continued
22
Creating a Client Application
continued
Cabin cabin_1 new Cabin()
cabin_1.setId(1) cabin_1.setName("Mast
er Suite") cabin_1.setDeckLevel(1)
cabin_1.setShipId(1)
cabin_1.setBedCount(3)
dao.createCabin(cabin_1) Cabin
cabin_2 dao.findCabin(1)
System.out.println(cabin_2.getName())
System.out.println(cabin_2.getDeckLevel())
System.out.println(cabin_2.getShipId())
System.out.println(cabin_2.getBedCount())
catch (javax.naming.NamingException
ne) ne.printStackTrace()
23
INSTALL.html
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Coming May 1, 2006
Enterprise JavaBeans 3.0 by Bill Burke and
Richard Monson-Haefel, OReilly, ISBN 059600978X