Enterprise Java Beans 3.0

Enterprise Java Bean 3.0

Filippo Diotalevihttp://www.diotalevi.com

[email protected]

Java User Group Milanohttp://www.jugmilano.it

February 16th, 2006

http://www.diotalevi.com/

mailto:[email protected]

JUG Milano – EJB 3.0 3

Filippo Diotalevi

http://www.diotalevi.com/weblog

http://www.jugmilano.it

https://java-champions.dev.java.net/


Tag-Cloud

StatefulSessionBean

JavaEE5

EnterpriseJavaBeansStatelessSessionBean

EntityBean

JavaPersistenceAPIGlassfish

Annotations

ResourceInjection

POJOMessageDrivenBean


JavaEE5

• EOD – Easy of Development

• Increase productivity

• Full backward compatibility

• Community involvement

Goals

POJOAnnotations

ResourceInjectionTools:


JavaEE5: Key new Specs

• Java Persistence API (JSR-220)• EJB 3.0 (JSR-220)• JavaServer Faces (JSR-252)• JAX-WS (JSR-224)• JAXB (JSR-222)• Common Annotations (JSR-250)• StAX (JSR-173)


EJB History

EJB 1.1 ( J2EE 1.2 ), 1999• Session beans (stateless & stateful), Entity Beans

• Remote interface

EJB 2.0 ( J2EE 1.3 ), 2001• Message-Driven Beans

• Entity 2.x and EJB QL

• Local and Remote interfaces

EJB 2.1 ( J2EE 1.4 ) 2003• EJB Timer Service

• Minor EJB QL enhancements


EJB 2.x Problems

• “Noisy”• Metadata XML Hell• Difficult test• Not truly OO• Pattern proliferation (DTO, Service Locator, ...)


EJB 3: Solutions

• POJO Model• Annotations• “Configuration by exception”• Java Persistence API


@Stateless Session Bean

• No more Home interfaces!• A POJI Business Interface (optional!) Annotated with @Remote or @Local

• A POJO Implementation Annotated with @Stateless

• No more deployment descriptors! (optional)


public interface Calculator { public int sum(int a, int b);}

@Stateless public class CalculatorImpl implements Calculator { public int sum(int a, int b) { return a + b; }}

@Stateless Session Bean

@Remote@Local

..or default (@Local)


Transaction Management@Stateless public class CalculatorImpl implements Calculator { @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW) public int sum(int a, int b) { //.... }

TransactionAttributeType.MANDATORY

TransactionAttributeType.REQUIRED

TransactionAttributeType.REQUIRES_NEW

TransactionAttributeType.SUPPORTS

TransactionAttributeType.NOT_SUPPORTED

TransactionAttributeType.NEVER


@Stateful Session Bean

• No more Home interfaces!• A POJI Business Interface (optional!) Annotated with @Remote or @Local

• A POJO Implementation Annotated with @Stateful



@Localpublic interface CounterEjb {

public int count();public void reset();

}

@Statefulpublic class CounterEjbImplementation implements CounterEjb {

private int count = 0;public int count() {

return ++count;}public void reset() {

count = 0;}

}

@Stateful Session Bean


@PostConstruct

@PostActivate

@PrePassivate

@PreDestroy

Other features

Callback methods

@Interceptors Declare interceptor classes (@Interceptors)

Develop an interceptor (POJO!)

Annotate interceptor's methods with @AroundInvoke


@EJB Invocation & dependency injectionpublic class CountServlet extends HttpServlet{

@EJBpublic CounterEjb counter;

protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException,IOException {

counter.count();}

} Dependency injection can only be used by managed classesServlet, listener classes, web services end-point, JAX-RPC handlers, EJB, interceptors, web services end-point


Java Persistence API

• Separate specification document • Produced by EJB 3.0 EG (JSR-220)• Available in & outside the Java EE container


@Entity Beans

• No more Home interfaces!• No Business Interfaces!• A POJO Implementation Annotated with @Entity

• A simple deployment descriptor


@Entity Beans@Entitypublic class Item implements Serializable{

private Long id;private String name;

@Id@GeneratedValue(strategy = GenerationType.AUTO)public Long getId() { return id; }public void setId(Long id) { this.id = id; }

public String getName() { return name;}public void setName(String name) { this.name = name; }

}

Primary KeyId auto generation

(if not transient) Properties are automatically persisted


EntityManager

• A detyped “home” interface• create(), merge() and remove() instances• Factory for Query


EntityManager@Statelesspublic class PaginaDAOImpl implements PaginaDAO {

@PersistenceContext EntityManager entityManager;

public void salva(Pagina pagina) { entityManager.merge(pagina);

}public void elimina(Pagina pagina) {

entityManager.remove(pagina);}public Pagina leggi(String titolo) {

Pagina p = entityManager.find(Pagina.class, titolo);}

EntityManager injected!


@PersistenceContext ?

persistence context as "a set of entity instances in which - for any persistent entity identity -there is a unique entity instance."

A persistence unit is a set of classes that are mapped to a single data store

persistence unit #2


Query

Query query = entityManager.createQuery("SELECT p FROM Pagina p");return query.getResultList();

• Query parameters• Support for pagination• Native query

entityManager.createNativeQuery()


Deployment Descriptor

Need to define the Persistence Unit in persistence.xml

<?xml version="1.0" encoding="UTF-8"?><persistence xmlns="http://java.sun.com/xml/ns/persistence"> <persistence-unit name="defaultPersistenceUnit" transaction-type="JTA"> <jta-data-source>jdbc/__default</jta-data-source> <properties> <property name="toplink.platform.class.name" value="oracle.toplink.essentials.platform.database.DerbyPlatform"/> </properties> </persistence-unit></persistence> Glassfish configuration


Entity Beans: advanced features

• Associations @OneToOne

@OneToMany

@ManyToOne

@ManyToMany

• Support for inheritance @Inheritance > 3 inheritance strategies: SINGLE TABLE

TABLE PER CLASS

JOINED TABLES

• Support for “cascadable” associations (@Cascade)• Support for optmistic locking (@Version)


EJB Query Language

• Very similar to HQL (Hibernate Query Language)• Support for polymorphic queries• Support for native queries• Subselects

UPDATE Customer cSET c.status = 'outstanding'WHERE c.balance < 10000


@MessageDriven Bean

• The Business Interface is the message listener interface (for JMS, javax.jms.MessageListener)

• A POJO Implementation Annotated with @MessageDriven



Open Source EJB3 Implementations

http://jonas.objectweb.org/

http://www.jboss.org

https://glassfish.dev.java.net/

To be released: Open JPA (Solarmetric KODO)


@Questions?

Thank you!


References• JSR 220: Enterprise JavaBeansTM 3.0http://www.jcp.org/en/jsr/detail?id=220

• Glassfish website and documentationhttps://glassfish.dev.java.net

• JBoss website and documentationhttp://www.jboss.org

• Gavin King's “Entity Beans in EJB 3” http://hibernate.org/gavin/ebejb3.pdf

• Kenneth Saks “Enterprise Java Bean 3.0”http://www.javasig.com/Archive/lectures/JavaSIG-EJB30.pdf

• Filippo Diotalevi's “Java EE 5 – Step by Step”http://www.diotalevi.com/weblog/?page_id=125

https://glassfish.dev.java.net/

http://www.jboss.org/

http://hibernate.org/gavin/ebejb3.pdf

http://www.javasig.com/Archive/lectures/JavaSIG-EJB30.pdf

Enterprise Java Beans 3.0

Technology

Transcript of Enterprise Java Beans 3.0