Test illustration isolation

TheTest.java

import static org.hibernate.testing.transaction.TransactionUtil2.inSession;
import static org.hibernate.testing.transaction.TransactionUtil2.inTransaction;

class TheTest {
  @Test
  public void testIsolation() {
    // open the "writing Session"
    inSession(
      getTheSessionFactory(),
      writingSession -> {
        // start a transaction against the "writing Session" and update the data
        inTransaction(
          writingSession,
          
          // get your entity and update its state
          final YourEntity data = writingSession.find( YourData.class, theId );
          data.setYourAttribute( newValue );

          // flush "writing Session" (but do not commit!).  This performs the UPDATE(s).
          // However, because the transaction is not committed, other transactions will
          // not yet be able to see it.  This is called transaction-isolation and is a
          // GoodThing(tm)
          writingSession.flush();
          
          // meanwhile open the "reading Session" and start a transaction
          inTransaction(
            getTheSessionFactory(),
            readingSession -> {
              // try to read the updated
              final YourEntity isolatedData = readingSession.find( YourData.class, theId );
              
              // the "reading Session" will not (yet) see the change (but uncommited) state.
              //
              // NOTE: based on the exact isolation configured for your driver/database
              // this may also block until the "writing Session" transaction has committed
              // releasing the database "resource locks" or may also throw a "deadlock"
              // type exception
              // 
              // Again, this is all called transaction isolation and is a GoodThing(tm).
              // And a standard ANSI SQL thing.  Not even close to a "Hibernate/Oracle bug"
              assertFalse( newValue, isolatedData.getYourAttribute() );
              assertTrue( originalValue, isolatedData.getYourAttribute() );
            }
          );
          
          // assuming the attempted read above did not block or throw the exception,
          // at this point the transaction associated with the "writing Session" has
          // been committed and we should be able to open a "reading Session" and see 
          // the changed state...
      }
    );

    final Session writingSession = openSession();
    final Session readingSession = openSession();
    
    inTransaction(
      
    );
  }
}