JPA - persistence.xml

About

The JPA specification requires the use of a persistence.xml file for deployment.

The persistence configuration file must be named “META-INF/persistence.xml” in the persistence archive.

This file defines one or more persistence unit where:

the provider node define the provider
the class nodes define the entity class
the properties nodes define the persistence properties of the provider.

The Xsd for the persistence configuration file can be found:

Persistence_2_0
or in the specification

Articles Related

Schema

Persistence configuration files must indicate

the persistence schema by using the persistence namespace:

http://java.sun.com/xml/ns/persistence

and indicate the version of the schema by using the version element as shown below:

<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_2_0.xsd"
             version="2.0">
...
</persistence>

Node

Provider

The provider node define the entity managers class. The provider element is optional but should be specified if the application is dependent upon a particular persistence provider being used. The class must be present in the classpath.

For EclipseLink:

<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>

For Hibernate:

<provider>org.hibernate.ejb.HibernatePersistence</provider>

For Toplink:

<provider>oracle.toplink.essentials.PersistenceProvider</provider>

exclude-unlisted-classes

<exclude-unlisted-classes>false</exclude-unlisted-classes>

All the class that are unlisted will/or not be automatically discovered with reflection. Ie if the @Entity annotations is present, the class is an entity.

Example

SE

Eclipselink configuration for a derby database with Logging level as properties

<?xml version="2.0" encoding="UTF-8"?>
<persistence version="1.0" 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_2_0.xsd">
  <persistence-unit name="TroubleTicketSystemServer" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>com.oracle.ticketsystem.beans.Tickethistory</class>
	<class>com.oracle.ticketsystem.beans.Ticket</class>
	<class>com.oracle.ticketsystem.beans.Technicianprivatedata</class>
	<class>com.oracle.ticketsystem.beans.Product</class>
	<class>com.oracle.ticketsystem.beans.Department</class>
	<class>com.oracle.ticketsystem.beans.Technician</class>
    <properties>
      <property name="eclipselink.target-database" value="Derby"/>            
      <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/>
      <property name="javax.persistence.jdbc.url" value="jdbc:derby://localhost:1527/jpatutorial;create=true"/>
      <property name="javax.persistence.jdbc.user" value="app"/>
      <property name="javax.persistence.jdbc.password" value="app"/>
      <property name="eclipselink.logging.level" value="ALL"/>            
    </properties>
  </persistence-unit>
</persistence>

Add the derby jars to the application classpath

EE

<persistence version="2.0" 
    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_2_0.xsd">
    <persistence-unit name="example" transaction-type="JTA">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <jta-data-source>localJTA</jta-data-source>
        <!-- optional --><class>org.eclipse.persistence.example.business.Cell</class>
        <properties>
            <!-- optional --><property name="eclipselink.target-database" 
                      value="org.eclipse.persistence.platform.database.DerbyPlatform"/>
            <property name="eclipselink.target-server" value="WebLogic_10"/>
            <property name="eclipselink.logging.level" value="FINEST"/>
        </properties>       
    </persistence-unit>
</persistence>

Add derby jars to the application server classpath (Example: for WebLogic place in the modules directory)

Support

No Persistence provider for EntityManager

Exception in thread "main" javax.persistence.PersistenceException: No Persistence provider for EntityManager named myProviderUnit:  
The following providers:
oracle.toplink.essentials.PersistenceProvider
oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider
Returned null to createEntityManagerFactory.
	at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:154)
	at test.Main.main(Main.java:51)

No persistence provider node with the name myProviderUnit can be found.

Documentation / Reference

See chapter 8.2.1 of the specification
EclipseLink/Examples/JPA/Derby