JPA: Reuse persistence.xml with jta-data-source in JSE and JUnit by overriding the datasource

Question

I have this peristence.xml that deploys on WildFly:

  <persistence-unit name="optaweb-employee-rostering-persistence-unit" transaction-type="JTA">
    <jta-data-source>java:jboss/datasources/ExampleDS</jta-data-source>
    ...
  </persistence-unit>

Now I'd like to reuse it in a plain Java application, with a direct JDBC connection, so without JNDI :

    Map<String, String> properties = new HashMap<>();
    properties.put("javax.persistence.jdbc.driver", "org.hsqldb.jdbcDriver");
    properties.put("javax.persistence.jdbc.url", "jdbc:hsqldb:mem:testdb");
    properties.put("javax.persistence.jdbc.user", "sa");
    properties.put("javax.persistence.jdbc.password", "");

    // Overwrites transaction-type successfully 
    properties.put("javax.persistence.transactionType", "RESOURCE_LOCAL");

    // TODO overwrite jta-data-source

    EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory(
            "optaweb-employee-rostering-persistence-unit", properties);

How do I overwrite jta-data-source ?

---

I've tried a number of JPA properties to override jta-data-source , with no success:

    // Overwrites jta-data-source
    // but triggers a JNDI lookup of "" which crashes of course
    properties.put("javax.persistence.jtaDataSource", "");
    // Does not overwrite jta-data-source
    properties.put("javax.persistence.jtaDataSource", null);

    // Does not overwrite jta-data-source
    properties.put("javax.persistence.nonJtaDataSource", "foo");

I've also tried a number of hibernate specific properties, such as hibernate.transaction.coordinator_class and hibernate.connection.datasource with the same failing results as above.

Answer 1

As far as I can tell from the source of Hibernate ORM (in particular org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl#EntityManagerFactoryBuilderImpl(org.hibernate.jpa.boot.spi.PersistenceUnitDescriptor, java.util.Map, java.lang.ClassLoader, org.hibernate.boot.registry.classloading.spi.ClassLoaderService) ), these particular JPA settings override settings from hibernate.properties or from the Map you will provide to Persistence.createEntityManagerFactory .

It may be a dumb idea, but can't you just do the opposite, ie not set the datasource in your persistence unit, but set it through a hibernate.properties file in your WildFly application? Then you can do whatever you want in your plain java application.