Beispiel: Einfache Container Managed Entity Bean

@NamedQuery (name="findAllKuchen", query="select o from KuchenSimpleBean o")
@Entity()
public class KuchenSimple implements Serializable
{

@NamedQueries({
  @NamedQuery (name="findAllKuchen", query="select o from KuchenSimpleBean o"),
  @NamedQuery (name="findByName", query="select o from KuchenSimpleBean o where o.name like ?1")
  })

@NamedQuery (name="findAllKuchen", query="from KuchenSimpleBean") 

  private Integer intId;
  private String strName;
  
  @Column()
  @Id ()
  @GeneratedValue () 
  public Integer getId()
  {
    return this.intId;
  }

  public void setId(Integer int_Id)
  {
    this.intId = int_Id;
  }
  
  @Column()
  public String getName()
  {
    return this.strName;
  }

  public void setName(String str_Name)
  {
    this.strName = str_Name;
  } 

	<?xml version="1.0" encoding="UTF-8"?>
	<persistence xmlns="http://java.sun.com/xml/ns/persistence"
		xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
		version="1.0">
		<persistence-unit name="kuchenPersistenceUnit">
			<jta-data-source>java:/DefaultDS</jta-data-source>
			<properties>
				<!-- Setzen dieser Property aktiviert das automatische Tabellen-Generieren und Löschen beim Deploy! -->
				<property name="hibernate.hbm2ddl.auto" value="create-drop" />
				<!-- SQL-Logging einschalten: -->
				<property name="hibernate.show_sql" value="true"></property>
			</properties>
		</persistence-unit>
	</persistence> 

@Remote
public interface KuchenWorker
{ 

  public void saveKuchen (KuchenSimpleBean kuchen);
  
  public void deleteKuchen (KuchenSimpleBean kuchen);
  
  public List getKuchen(); 

@Stateless
public class KuchenWorkerBean implements KuchenWorker 
{ 

  @PersistenceContext(unitName="kuchenPersistenceUnit")
  EntityManager entityManager = null;

    this.entityManager.merge(kuchen);

	<ejb-ref>
		<ejb-ref-name>ejb/KuchenWorker</ejb-ref-name>
		<ejb-ref-type>Session</ejb-ref-type>
		<home>java.lang.Object</home>
		<remote>de.fhw.swtvertiefung.knauf.kuchen.KuchenWorker</remote>
	</ejb-ref> 

	<?xml version="1.0" encoding="UTF-8"?>
	<!DOCTYPE jboss-client PUBLIC "-//JBoss//DTD Application Client 4.0//EN" "http://www.jboss.org/j2ee/dtd/jboss-client_4_0.dtd" >
	<jboss-client>
		<jndi-name>KuchenSimpleClient</jndi-name>
		<ejb-ref>
			<ejb-ref-name>ejb/KuchenWorker</ejb-ref-name>
			<jndi-name>KuchenSimple/KuchenWorkerBean/remote</jndi-name>
		</ejb-ref>
	</jboss-client> 

      Hashtable props = new Hashtable();
      props.put(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NamingContextFactory");
      props.put(Context.URL_PKG_PREFIXES, "org.jboss.naming.client");
      props.put(Context.PROVIDER_URL, "jnp://localhost:1099");
      props.put("j2ee.clientName", "KuchenSimpleClient");

      InitialContext initialContext = new InitialContext(props);
      
      Object objKuchen = initialContext.lookup("java:comp/env/ejb/KuchenWorker");
      this.kuchenWorker = (KuchenWorker) PortableRemoteObject.narrow(objKuchen, KuchenWorker.class); 

	Manifest-Version: 1.0
	Class-Path: KuchenSimpleEJB.jar
	Main-Class: de.fhw.swtvertiefung.knauf.kuchen.KuchenApplicationClient

2006-09-13 20:28:24,437 DEBUG [org.hibernate.persister.entity.AbstractEntityPersister] Static SQL for entity: de.fhw.swtvertiefung.knauf.kuchen.KuchenSimpleBean
2006-09-13 20:28:24,437 DEBUG [org.hibernate.persister.entity.AbstractEntityPersister]  Version select: select id from KuchenSimpleBean where id =?
2006-09-13 20:28:24,437 DEBUG [org.hibernate.persister.entity.AbstractEntityPersister]  Snapshot select: select kuchensimp_.id, kuchensimp_.name as name0_ from KuchenSimpleBean kuchensimp_ where kuchensimp_.id=?
2006-09-13 20:28:24,437 DEBUG [org.hibernate.persister.entity.AbstractEntityPersister]  Insert 0: insert into KuchenSimpleBean (name, id) values (?, ?)
2006-09-13 20:28:24,437 DEBUG [org.hibernate.persister.entity.AbstractEntityPersister]  Update 0: update KuchenSimpleBean set name=? where id=?
2006-09-13 20:28:24,437 DEBUG [org.hibernate.persister.entity.AbstractEntityPersister]  Delete 0: delete from KuchenSimpleBean where id=?
2006-09-13 20:28:24,437 DEBUG [org.hibernate.persister.entity.AbstractEntityPersister]  Identity insert: insert into KuchenSimpleBean (id, name) values (null, ?)
2006-09-13 20:28:24,453 DEBUG [org.hibernate.loader.entity.EntityLoader] Static select for entity de.fhw.swtvertiefung.knauf.kuchen.KuchenSimpleBean: select kuchensimp0_.id as id0_0_, kuchensimp0_.name as name0_0_ from KuchenSimpleBean kuchensimp0_ where kuchensimp0_.id=?
2006-09-13 20:28:24,453 DEBUG [org.hibernate.loader.entity.EntityLoader] Static select for entity de.fhw.swtvertiefung.knauf.kuchen.KuchenSimpleBean: select kuchensimp0_.id as id0_0_, kuchensimp0_.name as name0_0_ from KuchenSimpleBean kuchensimp0_ where kuchensimp0_.id=?
2006-09-13 20:28:24,453 DEBUG [org.hibernate.loader.entity.EntityLoader] Static select for entity de.fhw.swtvertiefung.knauf.kuchen.KuchenSimpleBean: select kuchensimp0_.id as id0_0_, kuchensimp0_.name as name0_0_ from KuchenSimpleBean kuchensimp0_ where kuchensimp0_.id=?
2006-09-13 20:28:24,453 DEBUG [org.hibernate.loader.entity.EntityLoader] Static select for entity de.fhw.swtvertiefung.knauf.kuchen.KuchenSimpleBean: select kuchensimp0_.id as id0_0_, kuchensimp0_.name as name0_0_ from KuchenSimpleBean kuchensimp0_ where kuchensimp0_.id=?
2006-09-13 20:28:24,468 DEBUG [org.hibernate.loader.entity.EntityLoader] Static select for action ACTION_MERGE on entity de.fhw.swtvertiefung.knauf.kuchen.KuchenSimpleBean: select kuchensimp0_.id as id0_0_, kuchensimp0_.name as name0_0_ from KuchenSimpleBean kuchensimp0_ where kuchensimp0_.id=?
2006-09-13 20:28:24,468 DEBUG [org.hibernate.loader.entity.EntityLoader] Static select for action ACTION_REFRESH on entity de.fhw.swtvertiefung.knauf.kuchen.KuchenSimpleBean: select kuchensimp0_.id as id0_0_, kuchensimp0_.name as name0_0_ from KuchenSimpleBean kuchensimp0_ where kuchensimp0_.id=?

2006-09-13 20:28:24,484 INFO  [org.hibernate.tool.hbm2ddl.SchemaExport] Running hbm2ddl schema export
2006-09-13 20:28:24,484 DEBUG [org.hibernate.tool.hbm2ddl.SchemaExport] import file not found: /import.sql
2006-09-13 20:28:24,484 INFO  [org.hibernate.tool.hbm2ddl.SchemaExport] exporting generated schema to database
2006-09-13 20:28:24,484 DEBUG [org.hibernate.tool.hbm2ddl.SchemaExport] drop table KuchenSimpleBean if exists
2006-09-13 20:28:24,484 DEBUG [org.hibernate.tool.hbm2ddl.SchemaExport] create table KuchenSimpleBean (id integer generated by default as identity (start with 1), name varchar(255), primary key (id))
2006-09-13 20:28:24,484 INFO  [org.hibernate.tool.hbm2ddl.SchemaExport] schema export complete 

<?xml version="1.0" encoding="UTF-8"?>
<ejb-jar version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                           http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd">
	<display-name>KuchenSimpleEJB</display-name>
	<enterprise-beans>
		<session>
			<description>
				<![CDATA[Stateless Session Bean für den Zugriff auf die Entitiy Bean
 * "Kuchen". Enthält Methoden zum Speichern und Löschen eines einzelnen
 * Kuchens sowie zum Holen einer Liste aller Kuchen.]]>
			</description>
			<display-name>KuchenWorkerBean</display-name>
			<ejb-name>KuchenWorkerBean</ejb-name>
			<remote>de.fhw.swtvertiefung.knauf.kuchen.KuchenWorker</remote>
			<ejb-class>de.fhw.swtvertiefung.knauf.kuchen.KuchenWorkerBean</ejb-class>
			<session-type>Stateless</session-type>
			<!--EntityManager-Injection -->
			<persistence-context-ref>
				<persistence-context-ref-name>KuchenPersistenceUnitRef</persistence-context-ref-name>
				<persistence-unit-name>kuchenPersistenceUnit</persistence-unit-name>
				<injection-target>
					<injection-target-class>
						de.fhw.swtvertiefung.knauf.kuchen.KuchenWorkerBean
					</injection-target-class>
					<injection-target-name>entityManager</injection-target-name>
				</injection-target>
			</persistence-context-ref>
		</session>
		<entity>
			<description>
				<![CDATA[Entity Bean für einen einzelnen Kuchen.]]>
			</description>
			<display-name>KuchenSimpleBean</display-name>
			<ejb-name>KuchenSimpleBean</ejb-name>
			<ejb-class>de.fhw.swtvertiefung.knauf.kuchen.KuchenSimpleBean</ejb-class>
			<persistence-type>Container</persistence-type>
			<prim-key-class>java.lang.Integer</prim-key-class>
			<reentrant>false</reentrant>
		</entity>
	</enterprise-beans>
</ejb-jar> 

• Injection des Persistence Context in die Session Bean (wobei das Pflichtelement "persistence-context-ref-name" für uns keine Bedeutung hat, das ist nur relevant wenn der Persistence Context per JNDI-Lookup geholt werden muss).
• Bei der EntityBean sind die oben markierten Angaben Pflicht. "persistence-type" gibt an ob der Container oder die Bean selbst sich um die Datenbankzugriffe kümmert. Bei einer EntityBean gemäß EJB3-Spezifikation ist hier natürlich "Container" die einzig sinnvolle Angabe. Die "prim-key-class" gibt den Datentyp des Primary Keys an, hier "java.lang.Integer". "reentrant" gibt an ob man ausgehend von einer Methode der Bean zu einer anderen Bean und wieder zurück laufen kann. Für unsere Bedürfnisse können wir hier immer "true" nehmen.

<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm http://java.sun.com/xml/ns/persistence/orm_1_0.xsd"
	version="1.0">
	<named-query name="findAllKuchen">
		<query>select o from KuchenSimpleBean o</query>
	</named-query>

	<entity class="de.fhw.swtvertiefung.knauf.kuchen.KuchenSimpleBean" access="PROPERTY"
	 metadata-complete="true">
		<table name="KUCHENSIMPLEBEAN"></table>
		<attributes>
			<id name="id">
				<column name="ID" /> 
				<generated-value/>
			</id>
			<basic name="name">
				<column name="NAME" />
			</basic>
		</attributes>
	</entity>

</entity-mappings> 

  @Column()
  @Id()
  public Integer getId()
  {
    return this.intId;
  } 

@NamedQueries( { 
  @NamedQuery(name = "findAllKuchen", query = "select o from KuchenSimpleBean o"),
  @NamedQuery(name = "getMaxKuchenId", query = "select max (o.id) from KuchenSimpleBean o")
  })
public class KuchenSimpleBean implements Serializable
{
  ...

  public void saveKuchen (KuchenSimpleBean kuchen)
  {
    if (kuchen.getId() == null)
    {
      Query query = this.entityManager.createNamedQuery("getMaxKuchenId");
      Integer intMaxId = (Integer) query.getSingleResult();
      //Beim ersten Aufruf kommt hier NULL zurück weil keine ID da ist.
      if (intMaxId == null)
      {
        //Wir starten mit der ID "1"
        kuchen.setId(1);
      }
      else
      {
        //MaxID + 1 verwenden:
        kuchen.setId(intMaxId + 1);
      }
    }
    this.entityManager.merge(kuchen);
  } 

	kuchen.setId( new Integer (intMaxId.intValue() + 1));