Hibernate User Guide

Entity value encoding

Value encoders are automatically created for all mapped Hibernate entity types. This is done by encoding the entity as it's id (coerced to a String) and decoding the entity by looking it up in the Hibernate Session using the encoded id. Consider the following example:

public class ViewPerson
{
  @Property
  private Person person;
  
  void onActivate(Person person)
  {
    this.person = person;
  }
  
  Person onPassivate()
  {
    return person;
  }
}
<html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_1_0.xsd">
<body>
  The person's name is: ${person.name}
</body>
</html>

Accessing the page as /viewperson/152 would load the Person entity with id 152 and use that as the page context.

Using @PageActivationContext

If you prefer to use annotations, you may let Tapestry generate the page activation context handlers for you. Relying on an existing ValueEncoder for the corresponding property you can use the @PageActivationContext annotation. The disadvantage is that you can't access the handlers in a unit test.

public class ViewPerson
{
  @Property
  @PageActivationContext
  private Person person;
  
}

Using @Persist with entities

If you wish to persist an entity in the session, you may use the "entity" persistence strategy:

public class ViewPerson
{
  @Persist("entity")
  @Property
  private Person person;
  
  void onActivate(Person person)
  {
    this.person = person;
  }
  
}

This persistence strategy works with any Hibernate entity that is associated with a valid Hibernate Session by persisting only the id of the entity. Notice that no onPassivate() method is needed; when the page renders the entity is loaded by the id stored in the session.

Using @SessionState with entities

Added in 5.2

The default strategy for persisting Session State Objects is "session". Storing a Hibernate entity into a <HttpSession> is problematic because the stored entity is detached from the Hibernate session. Similar to @Persist("entity") you may use the "entity" persistence strategy to persist Hibernate entities as SSOs:

public class Index
{
  @SessionState
  @Property
  private Person person;
  
  ...
  
}

For this purpose you need to set the value of the symbol <HibernateSymbols.ENTITY_SESSION_STATE_PERSISTENCE_STRATEGY_ENABLED> to <true>:

public class AppModule
{
    public static void contributeApplicationDefaults(MappedConfiguration<String, String> configuration)
    {
        configuration.add(HibernateSymbols.ENTITY_SESSION_STATE_PERSISTENCE_STRATEGY_ENABLED, "true");
    }
}

Alternatively you can apply the "entity" persistence strategy to a single Hibernate entity:

public class AppModule
{
    public void contributeApplicationStateManager(MappedConfiguration<Class, ApplicationStateContribution> configuration)
    {
    	configuration.add(Person.class, new ApplicationStateContribution(HibernatePersistenceConstants.ENTITY));
    }
}

Committing Changes

All Hibernate operations occur in a transaction, but that transaction is aborted at the end of each request; thus any changes you make will be lost unless the transaction is committed.

The correct way to commit the transaction is via the @CommitAfter annotation:

public class EditPerson
{
  @Persist("entity")
  @Property
  private Person person;

  @InjectPage
  private PersonIndex personIndex;

  void onActivate(Person person)
  {
    this.person = person;
  }

  Object onPassivate() { return person; }

  @CommitAfter
  Object onSuccess()
  {
    return personIndex;
  }
}

In this example, the Person object may be updated by a form; the form's success event handler method, onSuccess() has the @CommitAfter annotation.

Behind the scenes, the @CommitAfter annotation causes the HibernateSessionManager's commit() method to be executed before the method returns.

The transaction will be committed when the method completes normally.

The transaction will be aborted if the method throws a RuntimeException.

The transaction will be committed if the method throws a checked exception (one listed in the throws clause of the method).

Managing Transactions using DAOs

As your application grows, you will likely create a Data Access Object layer between your pages and the Hibernate APIs.

The @CommitAfter annotation can be useful there as well.

You may use @CommitAfter on method of your service interface, then use a decorator to provide the transaction management logic.

First definine your DAO's service interface:

public interface PersonDAO
{
  Person findByName(String name);

  @CommitAfter
  void add(Person newPerson);

  @CommitAfter
  void update(Person person);

  @CommitAfter
  void delete(Person person);
}

Next, define your service in your application's Module class:

public class AppModule
{
   public static void bind(ServiceBinder binder)
   {
      binder.bind(PersonDAO.class, PersonDAOImpl.class);
   }
}

Finally, you should use the HibernateTransactionAdvisor to add transaction advice:

    @Match("*DAO")
    public static void adviseTransactions(HibernateTransactionAdvisor advisor, MethodAdviceReceiver receiver)
    {
        advisor.addTransactionCommitAdvice(receiver);
    }

This advice method is configured to match against any service whose id ends with "DAO", such as "PersonDAO".

The advisor scans the service interface and identifies any methods with the @CommitAfter annotation.