Here is an interesting one. I am beginning to modernise a Java application and have created a solution to a current requirement that entities can be persisted using database credentials other than those used to define the persistence unit's DataSource.

The ideal solution to the different credentials problem would be for the persistence provider to implement the javax.persistence.EntityManagerFactory.createEntityManager(Map) interface so that when new credentials are supplied, they are used. Apache OpenJPA does this but we are using Hibernate and it does not. So I created a Hibernate-specific solution for us that finds the org.hibernate.connection.ConnectionProvider instance and calls its configure method before calling createEntityManager().

It works well and calling the EJB that provides the business interface is like this:

@EJB
private RunningSheetManager manager;

    // In a method...
    manager.setCredentials(user, pass);
    manager.addRunningSheetEntry( /* params */ );

Then I tried creating a fluent interface to make the call something like:

@EJB
private RunningSheetManager manager;

    // In a method...
    manager.withCredentials(user, pass)
           .addRunningSheetEntry( /* params */ );

It all ran without error and Hibernate dumps all the same SQL statements to the console as before, but nothing was saved into the database! I can only conclude that the transaction was rolled back instead of being committed.

Has anybody seen this kind of behaviour before? Did I miss something in the use of fluent interfaces with EJBs? Perhaps this is a peculiarity of the app server or of Hibernate.

I ran this on OC4J 10.1.3.4 (a partial Java EE 5 implementation) and Hibernate 3.3.

Any thoughts? I have scrapped the fluent interface and restored the original one.

Adam

Thanks for your feedback. I know OC4J is EOL but our two major customers use it. They will migrate to WebLogic Server during the next 12 months so I am working with that.

Fluent Interface

The stuff about user credentials was the background to the reason for my original post. There is more detail about that below.

I had a servlet that injects a bean, then uses it like this:

    manager.setCredentials(user, pass);
    manager.doBusinessMethod(cat, dog);

It works as expected. But my fluent-interface version of the bean failed to commit the transaction in OC4J. The calling sequence was:

    manager.withCredentials(user, pass)
           .doBusinessMethod(cat, dog);

The difference is what happens to the manager object between the calls.

• In the fluent interface, the withCredentials method returns this and the business method is performed directly on it.
• In the original version, the container appears to do something with the object before the business method is called.

Have you seen anything like this elsewhere?

User credentials and EntityManagerFactory

I didn’t show you the intermediate classes, but I did create one that injects EntityManagerFactory. Here it is:

@Stateless
@Local(CredentialsEntityManagerFactory.class)
public class CredentialsEntityManagerFactoryBean
      implements CredentialsEntityManagerFactory {

  @PersistenceUnit
  private EntityManagerFactory emf;

  public EntityManager getEntityManager(String username, String password) {

    if (username == null || password == null) {
      throw new IllegalStateException("CredentialsEntityManagerFactoryBean: username and password must not be null");
    }

    if (emf instanceof HibernateEntityManagerFactory) {
      // Find the connection provider, which will be an instance of
      // org.hibernate.ejb.connection.InjectedDataSourceConnectionProvider
      // in an EJB.
      SessionFactory fact = ((HibernateEntityManagerFactory)emf).getSessionFactory();
      ConnectionProvider prov = ((SessionFactoryImplementor)fact).getConnectionProvider();
      // Username and password properties, if set, will be used by
      // a Hibernate connection provider when getting a connection from
      // the data source.
      Properties props = new Properties();
      props.setProperty(Environment.USER, username);
      props.setProperty(Environment.PASS, password);
      prov.configure(props);
    } else {
      throw new IllegalStateException("CredentialsEntityManagerFactoryBean requires Hibernate as the persistence provider");
    }

    return emf.createEntityManager();

  }

}

An example of its use is a stateless bean called RunningSheetManagerBean with:

  @EJB
  private CredentialsEntityManagerFactory cemf;

It also contains a setCredentials method and a business method that includes:

    EntityManager em = cemf.getEntityManager(username, password);
    try {
      em.persist(entry);
    } finally {
      // We must close the entity manager explicitly.
      em.close();
    }

—Michael