package com.atlassian.activeobjects.confluence.hibernate;
   
   import com.atlassian.hibernate.PluginHibernateSessionFactory;
   import com.atlassian.sal.api.transaction.TransactionCallback;
   import com.atlassian.sal.api.transaction.TransactionTemplate;
   import net.sf.hibernate.SessionFactory;
   import net.sf.hibernate.dialect.Dialect;
   import net.sf.hibernate.engine.SessionFactoryImplementor;
   
  import static com.google.common.base.Preconditions.checkNotNull;
  
  /**
   * Extracts the dialect from the {@link net.sf.hibernate.SessionFactory hibernate session factory}, provided the
   * concrete implementation, also implements {@link net.sf.hibernate.engine.SessionFactoryImplementor}.
   */
  public final class HibernateSessionDialectExtractor implements DialectExtractor {
      private final PluginHibernateSessionFactory sessionFactory;
  
      private final TransactionTemplate transactionTemplate;
  
      public HibernateSessionDialectExtractor(PluginHibernateSessionFactory sessionFactory, TransactionTemplate transactionTemplate) {
          this.sessionFactory = checkNotNull(sessionFactory);
          this.transactionTemplate = checkNotNull(transactionTemplate);
      }
  
      public Class<? extends Dialect> getDialect() {
          // hibernate needs a transaction to create the session
          return transactionTemplate.execute(new TransactionCallback<Class<? extends Dialect>>() {
              @Override
              public Class<? extends Dialect> doInTransaction() {
                  final SessionFactory hibernateSessionFactory = sessionFactory.getSession().getSessionFactory();
                  if (hibernateSessionFactory instanceof SessionFactoryImplementor) {
                      return ((SessionFactoryImplementor) hibernateSessionFactory).getDialect().getClass();
                  } else {
                      return null;
                  }
              }
          });
      }
  }