enterprise java beans 301641 (1)

7/28/2019 Enterprise Java Beans 301641 (1)

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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]:[email protected]://www.diotalevi.com/


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JUG Milano EJB 3.0 3

Filippo Diotalevi

http://www.diotalevi.com/weblog

http://www.jugmilano.it

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


4/30JUG Milano EJB 3.0 4

Tag-Cloud

StatefulSessionBean

JavaEE5

EnterpriseJavaBeansStatelessSessionBean

EntityBean

JavaPersistenceAPIGlassfishAnnotations

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, ServiceLocator, ...)



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);

}

@Statelesspublic 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


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@Stateful Session Bean


A POJI Business Interface (optional!)

Annotated with @Remote or @Local A POJO Implementation

Annotated with @Stateful



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@Local

public 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


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@PostConstruct

@PostActivate

@PrePassivate

@PreDestroy

Other features

Callback methods

@Interceptors

Declare interceptor classes (@Interceptors)Develop an interceptor (POJO!)

Annotate interceptor's methods with @AroundInvoke


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@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 servicesend-point

i


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Java Persistence API

Separate specification document Produced by EJB 3.0 EG

(JSR-220)

Available in & outside the

Java EE container

E tit B


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@Entity Beans


No Business Interfaces!

A POJO ImplementationAnnotated with @Entity

A simple deployment descriptor

E tit B


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@Entity Beans@Entity

public 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 Key

Id auto generation

(if not transient) Properties are automatically persisted

E tit M


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EntityManager

A detyped home interface

create(), merge() and

remove() instances

Factory for Query

E tit M


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EntityManager@Stateless

public 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!

@P i t C t t ?


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@PersistenceContext ?

persistence contextas "a set of entityinstances in which - for any persistent entityidentity -there is a unique entity instance."

Apersistence unitisa set of classes thatare mapped to asingle data store

persistence unit #2

Q er


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Query

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

return query.getResultList();

Query parameters Support for pagination

Native query

entityManager.createNativeQuery()

Deployment Descriptor


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Deployment Descriptor

Need to define the Persistence Unit inpersistence.xml

jdbc/__default

Glassfish configuration

Entity Beans: advanced features


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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


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EJB Query Language

Very similar to HQL (Hibernate Query Language)

Support for polymorphic queries

Support for native queries Subselects

UPDATE Customer c

SET c.status = 'outstanding'

WHERE c.balance < 10000

@MessageDriven Bean


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@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


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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?


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@Questions?

Thank you!

References


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References JSR 220: Enterprise JavaBeansTM 3.0

http://www.jcp.org/en/jsr/detail?id=220 Glassfish website and documentation

https://glassfish.dev.java.net

JBoss website and documentation

http://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
http://localhost/var/www/apps/conversion/tmp/scratch_14/https://glassfish.dev.java.net/http://www.jboss.org/http://hibernate.org/gavin/ebejb3.pdfhttp://www.javasig.com/Archive/lectures/JavaSIG-EJB30.pdfhttp://www.javasig.com/Archive/lectures/JavaSIG-EJB30.pdfhttp://hibernate.org/gavin/ebejb3.pdfhttp://www.jboss.org/https://glassfish.dev.java.net/http://localhost/var/www/apps/conversion/tmp/scratch_14/

enterprise java beans 301641 (1)

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