Initial commit of the Spanner Features code sample for Hibernate.

Demonstrates:

• Stale Reads
• Read-Only Transactions

Open Questions:

From my testing it seems like the Hibernate Sessions share the JDBC Connection. This means that if you set the connection to read-only like this:

    try (Session session = sessionFactory.openSession()) {
      session.beginTransaction();
      session.doWork(connection -> connection.setReadOnly(true));
      ... Do something ...
      session.getTransaction().commit();
    }

You will have to undo that later on by setting the connection to readOnly = false in the next connection. The setting will stay even when you open a new session.

    try (Session session = sessionFactory.openSession()) {
      session.beginTransaction();
      session.doWork(connection -> connection.setReadOnly(false));
      ... Do something ...
      session.getTransaction().commit();
    }

Would this break the multi-threaded use-case though? Will ask.