Q: Provider error: DatastorePersistenceProvider I'm trying to convert my hibernate-based GWT implementation into a JPA2 version. I've added the persistence.xml, the specific libraries and added some code just to open (by getting an entityManager). I just do a local employment, I do not use google's app engine (and I'm not intended to use it).
I get the following message:

Cannot connect to MySQL database
  server (Provider error. Provider:
  org.datanucleus.store.appengine.jpa.DatastorePersistenceProvider),
  exiting

My persistence.xml looks like:
<?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="mydatabase_dev">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>mypackage.Product</class>
    <class>mypackage.Expert</class>
    <class>mypackage.Person</class>
       <properties>
          <property name="hibernate.archive.autodetection" value="class, hbm"/>
             <property name="hibernate.show_sql" value="false"/>
              <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
              <property name="hibernate.connection.url" value="jdbc:mysql://myhost.mydomain/MYDATABASE"/>
              <property name="hibernate.connection.username" value="myusername"/>
              <property name="hibernate.connection.password" value="topsecret"/>
              <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
              <property name="hibernate.hbm2ddl.auto" value="update"/>

              <property name="hibernate.c3p0.min_size" value="5"/>
              <property name="hibernate.c3p0.max_size" value="20"/>
              <property name="hibernate.c3p0.timeout" value="300"/>
              <property name="hibernate.c3p0.max_statements" value="50"/>
              <property name="hibernate.c3p0.idle_test_period" value="3000"/>  
              <!-- Disable the second-level cache  -->
              <property name="cache.provider_class" value="org.hibernate.cache.NoCacheProvider"/>
           </properties>
    </persistence-unit>
</persistence>

There is no other error message, warning, stacktrace, etc.
What is wrong or in what way can I examine what the real problem is?

A: GAE/J doesn't do MySQL, nor JPA2 so why are you including it/specifying it in your persistence.xml? Perhaps if you post your persistence.xml then people can make an informed opinion ...
