anchor.diff:  - Indicators of unread messages get a color.
   - Read non-flagged messages don’t have an indicator at all.
   
  +[source, java]
  +----
       public void setIndicator(boolean read, Flag flag) {
           MyTheme.MESSAGE_STYLES.forEach(indicatorButton::removeStyleName);
           indicatorButton.setIcon(null);
  
positive.code: 
      List<Message> findByFlagIsNotNullAndTrashed(boolean trashed);
  }
  
  === Facade
  A simple stateless EJB facade accessing repositories. Inject your repository to the facade.
  
  @Stateless
  public class MessageFacade {
  
  
negative.code:     @PersistenceContext(unitName = "tutorialdb")
      public EntityManager entityManager;
  }
  ----
  
  === Entity
  In this simple example you only need a single JPA entity, which represents the listed message. An abstract entity here is a base class containing version and id fields.
  
  [source, java]
  ----
  @Entity
  public class Message extends AbstractEntity {
  
  