Google app engine and JPA with Eclipse plug-in

Question

I created an application with JSF ( Primefaces) and JPA and I m trying to deploy it on GAE. First I m trying with the local app engine sdk. I have a problem when trying to use JPA with CloudSQL. I m following the instructions on how to do it using Eclipse here:

https://developers.google.com/eclipse/docs/cloudsql-jpatools

However I get the following error:

Caused by: javax.persistence.PersistenceException: Provider error. Provider: org.datanucleus.store.appengine.jpa.DatastorePersistenceProvider
    at javax.persistence.Persistence.createFactory(Persistence.java:176)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:112)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:66)
    at org.Handlers.EMFService.<clinit>(EMFService.java:8)
    ... 51 more
Caused by: java.lang.NullPointerException
    at org.datanucleus.jpa.EntityManagerFactoryImpl.initialisePMF(EntityManagerFactoryImpl.java:452)
    at org.datanucleus.jpa.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:355)
    at org.datanucleus.store.appengine.jpa.DatastoreEntityManagerFactory.<init>(DatastoreEntityManagerFactory.java:63)
    at org.datanucleus.store.appengine.jpa.DatastorePersistenceProvider.createEntityManagerFactory(DatastorePersistenceProvider.java:35)
    at javax.persistence.Persistence.createFactory(Persistence.java:172)
    ... 54 more

What s more is that I think that datanucleus is used to access the App engine Datastore. However I m trying to connect to the relational cloud sql database ( it s up and running). So i dont understand what the datanucleus has to do with that.

I m using Eclipselink for implementing the JPA spec as proposed by the following guide by GAE: https://developers.google.com/eclipse/docs/cloudsql-jpatools

Below you can also see the persistence.xml:

<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="googleeclipselink"
        transaction-type="RESOURCE_LOCAL">

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

        <class>org.entities.Department</class>
        <class>org.entities.Employee</class>
        <class>org.entities.Partner</class>
        <class>org.entities.Project</class>
        <class>org.entities.User</class>

        <properties>
            <!-- <property name="datanucleus.NontransactionalRead" value="true" /> 
                <property name="datanucleus.NontransactionalWrite" value="true" /> <property 
                name="datanucleus.ConnectionURL" value="appengine" /> -->
            <property name="javax.persistence.jdbc.driver"
                value="com.google.appengine.api.rdbms.AppEngineDriver" />
            <property name="javax.persistence.jdbc.url"
                value="jdbc:google:rdbms://fotisgonidisseerc:googlecloudsql/researchprojects" />
            <property name="javax.persistence.jdbc.user" value="" />
            <property name="javax.persistence.jdbc.password" value="" />
        </properties>
    </persistence-unit>
</persistence>

Anybody could give me a hint of how to solve it?

Firstly clarify what is your persistence.xml and which datastore you're deploying to ? As per the JPA spec, it will make use of the JPA implementation(s) in the CLASSPATH unless your persistence.xml defines which is to be used (and it is present in the CLASSPATH) — DataNucleus, Nov 26 '12 at 16:10

score 1 · Accepted Answer · answered Nov 27 '12 at 10:36

After spending some time on the issue I figured out that I had to remove the DataNucleus libs from the WEB-INF/lib. I also needed to add the EclipseLink lib in my classpath. This is because I m using EclipseLink as JPA implemetation.Therefore DataNucleus were causing a conflict and thus needs to be removed. I guess that Google Plug-in for Eclipse does this automatically but apparently sometimes it fails.

Google app engine and JPA with Eclipse plug-in

1 Answers1