Discussion :

[SpeedOverflow]

Bonjour,

Je débute avec JPA.

Je reçoit déjà un message d'erreur quand je lancement mon application

J'utilise le serveur MySql pour mes base de données.

Pourriez- vous me données une solution ou des pistes à suivre.

Merci

L'erreur qui est jeté:

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log4j:WARN No appenders could be found for logger (org.hibernate.ejb.Version).
log4j:WARN Please initialize the log4j system properly.
Exception in thread "main" javax.persistence.PersistenceException: No Persistence provider for EntityManager named helloworld
	at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
	at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
	at Application.main(Application.java:14)

le fichier de persistence:

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<?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="helloworld" transaction-type="RESOURCE_LOCAL">
		<!--  provider>org.hibernate.ejb.HibernatePersistence</provider>
		<class>helloworld.Message</class-->
		<properties>
			<property name="hibernate.archive.autodetection" value="class"/>
			<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
			<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/jpa1helloworld"/>
		    <property name="hibernate.connection.username" value="root"/>
		    <property name="hibernate.connection.password" value="root"/>
		    <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
		    <property name="hibernate.show_sql" value="true"/>
		    <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
		</properties>
	</persistence-unit>
</persistence>

et l'application

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import helloworld.Message;
 
import java.util.List;
 
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
 
public class Application {
 
	public static void main(String[] args) {
		// same in xml file
		EntityManagerFactory emf = Persistence.createEntityManagerFactory("helloworld");
		EntityManager em = emf.createEntityManager();
		EntityTransaction tx = em.getTransaction();
		tx.begin();
		Message message = new Message();
		message.setText("Using JPA with Hibernate");
		em.persist(message);
		Message message2 = new Message();
		message2.setText("Hello World");
		em.persist(message2);
		tx.commit();
		em.close();
 
		EntityManager newEm = emf.createEntityManager();
		EntityTransaction newTx = newEm.getTransaction();
		newTx.begin();
		List messages = newEm.createQuery("select m from Message m order by m.text asc").getResultList();
		System.out.println(messages.size() + "message(s) found:");
		for(Object m : messages){
			Message loadedMsg = (Message)m;
			System.out.println(loadedMsg.getText());
		}
		newTx.commit();
		newEm.close();
		emf.close();
	}
 
}

[DevServlet]

Il est dans quel repertoire ton persistence.xml?

[SpeedOverflow]

Il est dans quel repertoire ton persistence.xml?

/jpa1helloworld/src/resources/META-INF/persistence.xml

[DevServlet]

Essaie ca :

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@PersistenceContext(unitName="helloworld")
private EntityManager em;

[SpeedOverflow]

J'ai ouvert un projets JPA.

et voici ce qui m'affiche

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[EL Info]: 2011-07-25 14:38:08.234--ServerSession(23387093)--EclipseLink, version: Eclipse Persistence Services - 1.1.3.v20091002-r5404
[EL Severe]: 2011-07-25 14:38:08.25--ServerSession(23387093)--Local Exception Stack: 
Exception [EclipseLink-4021] (Eclipse Persistence Services - 1.1.3.v20091002-r5404): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Unable to acquire a connection from driver [null], user [null] and URL [null].  Verify that you have set the expected driver class and URL.  Check your login, persistence.xml or sessions.xml resource.  The jdbc.driver property should be set to a class that is compatible with your database platform
	at org.eclipse.persistence.exceptions.DatabaseException.unableToAcquireConnectionFromDriverException(DatabaseException.java:375)
	at org.eclipse.persistence.sessions.DefaultConnector.connect(DefaultConnector.java:90)
	at org.eclipse.persistence.sessions.DatasourceLogin.connectToDatasource(DatasourceLogin.java:162)
	at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:583)
	at org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:227)
	at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:255)
	at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.getServerSession(EntityManagerFactoryImpl.java:112)
	at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:164)
	at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:151)
	at model.EmployeeTest.main(EmployeeTest.java:12)
 
Exception in thread "main" javax.persistence.PersistenceException: Exception [EclipseLink-4021] (Eclipse Persistence Services - 1.1.3.v20091002-r5404): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Unable to acquire a connection from driver [null], user [null] and URL [null].  Verify that you have set the expected driver class and URL.  Check your login, persistence.xml or sessions.xml resource.  The jdbc.driver property should be set to a class that is compatible with your database platform
	at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:272)
	at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.getServerSession(EntityManagerFactoryImpl.java:112)
	at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:164)
	at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:151)
	at model.EmployeeTest.main(EmployeeTest.java:12)
Caused by: Exception [EclipseLink-4021] (Eclipse Persistence Services - 1.1.3.v20091002-r5404): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Unable to acquire a connection from driver [null], user [null] and URL [null].  Verify that you have set the expected driver class and URL.  Check your login, persistence.xml or sessions.xml resource.  The jdbc.driver property should be set to a class that is compatible with your database platform
	at org.eclipse.persistence.exceptions.DatabaseException.unableToAcquireConnectionFromDriverException(DatabaseException.java:375)
	at org.eclipse.persistence.sessions.DefaultConnector.connect(DefaultConnector.java:90)
	at org.eclipse.persistence.sessions.DatasourceLogin.connectToDatasource(DatasourceLogin.java:162)
	at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:583)
	at org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:227)
	at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:255)
	... 4 more

J'y comprend rien du tout

[DevServlet]

Il ne voit rien dans ton persistence.xml, il ne chope aucune des valeurs de ta datasource, tu le vois bien dans tes traces d'erreur.