How can I use derby in memory with jpa2? - eclipselink

Question

Regardless of the following persistence.xml configuration the database is persisted on disk.
<persistence-unit name="com.mysimpatico_inmemory_persistence_nbm_1.0-SNAPSHOTPU" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>com.mysimpatico.memoplatform.persistence.entities.Expression</class>
<properties>
<property name="javax.persistence.jdbc.url" value="jdbc:derby:memory:tempDb;create=true"/>
<property name="javax.persistence.jdbc.password" value=""/>
<property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/>
<property name="javax.persistence.jdbc.user" value=""/>
</properties>
http://wiki.apache.org/db-derby/InMemoryBackEndPrimer

Answer 1

I'm using Derby in memory for testing and my configuration is very close to yours.
Here is my persistence.xml:
<?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_2_0.xsd" version="2.0">
<persistence-unit name="TestPu" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>com.acme.Foo</class>
<class>com.acme.Bar</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<!-- Common properties -->
<property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/>
<property name="javax.persistence.jdbc.url" value="jdbc:derby:memory:test-jpa;create=true"/>
<property name="javax.persistence.jdbc.user" value="APP"/>
<property name="javax.persistence.jdbc.password" value="APP"/>
<!-- EclipseLink specific properties -->
<property name="eclipselink.target-database" value="Derby"/>
<property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
<property name="eclipselink.debug" value="ALL"/>
<property name="eclipselink.weaving" value="static"/>
<property name="eclipselink.logging.level" value="FINEST"/>
<property name="eclipselink.logging.level.sql" value="FINEST"/>
<property name="eclipselink.logging.level.cache" value="FINEST"/>
</properties>
</persistence-unit>
</persistence>
Where org.apache.derby:derby:jar:10.6.2.1 is on the classpath.
Now two questions/suggestions:
How do you know the database is persisted on disk?
If it really does, make sure you're using the persistence.xml you think you are.

Answer 2

Add the following to your maven configuration
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>3.3.2.GA</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.derby</groupId>
<artifactId>derby</artifactId>
<version>10.5.3.0</version>
<scope>test</scope>
</dependency>
The following persistance.xml works pretty well with hibernate.
<persistence-unit name="testPU" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class>myapp.model.entities.Group</class>
<class>myapp.model.entities.User</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<property name="hibernate.connection.url" value="jdbc:derby:memory:jpa"/>
<property name="hibernate.connection.driver_class" value="org.apache.derby.jdbc.EmbeddedDriver"/>
<property name="hibernate.dialect" value="org.hibernate.dialect.DerbyDialect"/>
<property name="hibernate.hbm2ddl.auto" value="create"/>
<property name="hibernate.connection.username" value=""/>
<property name="hibernate.connection.password" value=""/>
</properties>
</persistence-unit>