Question

I am newbie with JPA. I’m trying to run some sample code using JPA but I get the following exception:

javax.persistence.PersistenceException: No Persistence provider for EntityManager named MyJPAApplicationPU

I put my exception message here,

INFO: Could not find any META-INF/persistence.xml file in the classpath
javax.persistence.PersistenceException: No Persistence provider for EntityManager named MyJPAApplicationPU
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
        at com.myJpa.TestJPA.setUp(TestJPA.java:30)
        at com.myJpa.TestJPA.main(TestJPA.java:72)

Any help would be appreciated.

Answer 1

Well, the error is self explaining, you need to provide a META-INF/persistence.xml to use JPA. This file is used to define a “persistence unit”. From the JPA 1.0 specification:

6.2.1 persistence.xml file

A persistence.xml file defines a
persistence unit. It may be used to
specify managed persistence classes
included in the persistence unit,
object/relational mapping information
for those classes, and other
configuration information for the
persistence unit and for the entity
manager(s) and entity manager factory
for the persistence unit. The
persistence.xml file is located in
the META-INF directory of the root
of the persistence unit. This
information may be defined by
containment or by reference, as
described below.

Here is a sample persistence.xml for a Java SE environment (using Hibernate as JPA provider):

<?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="MyJPAApplicationPU" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <class>com.mycompany.Foo</class>
        <class>com.mycompany.Bar</class>
        <exclude-unlisted-classes>true</exclude-unlisted-classes>
        <properties>
            <property name="hibernate.connection.provider_class" value="org.hibernate.connection.DriverManagerConnectionProvider" />
            <property name="hibernate.connection.url" value="jdbc:hsqldb:mem:unit-testing-jpa"/>
            <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
            <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
            <property name="hibernate.connection.username" value="sa"/>
            <property name="hibernate.connection.password" value=""/>
            <property name="hibernate.show_sql" value="true"/>
        </properties>
    </persistence-unit>
</persistence>

Some comments about the above file:

• when running in a Java SE environment, you cannot rely on JTA and the transaction type must be RESOURCE_LOCAL (which is actually the default in a Java SE environment but specifying it make it more clear).
• when running in a Java SE environment, you cannot use a JDNI data source and the provider will obtain connections directly from the JDBC driver so you must pass the relevant informations to the provider (driver class name, connection url, user, password). With JPA 1.0 the properties used to pass these metadata are provider specific.
• To insure the portability of a Java SE application, it is necessary to explicitly list the managed persistence classes that are included in the persistence unit.