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package javax.persistence;

/**
 * Utility interface between the application and the persistence provider managing the persistence unit.
 * 
 * The methods of this interface should only be invoked on entity instances obtained from or managed by entity managers for this persistence
 * unit or on new entity instances.
 */
public interface PersistenceUnitUtil extends PersistenceUtil {
	/**
	 * Return the id of the entity. A generated id is not guaranteed to be available until after the database insert has occurred. Returns
	 * null if the entity does not yet have an id.
	 * 
	 * @param entity
	 *            entity instance
	 * @return id of the entity
	 * @throws IllegalArgumentException
	 *             if the object is found not to be an entity
	 */
	public Object getIdentifier(Object entity);

	/**
	 * Determine the load state of an entity belonging to the persistence unit. This method can be used to determine the load state of an
	 * entity passed as a reference. An entity is considered loaded if all attributes for which FetchType EAGER has been specified have been
	 * loaded. The isLoaded(Object, String) method should be used to determine the load state of an attribute. Not doing so might lead to
	 * unintended loading of state.
	 * 
	 * @param entity
	 *            entity whose load state is to be determined
	 * @return false if the entity has not been loaded, else true
	 */
	@Override
	public boolean isLoaded(Object entity);

	/**
	 * Determine the load state of a given persistent attribute of an entity belonging to the persistence unit.
	 * 
	 * @param entity
	 *            entity instance containing the attribute
	 * @param attributeName
	 *            name of attribute whose load state is to be determined
	 * @return false if entity's state has not been loaded or if the attribute state has not been loaded, else true
	 */
	@Override
	public boolean isLoaded(Object entity, String attributeName);
}