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/*
 * Copyright 2010 Bull S.A.S.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package javax.persistence;


/**
 * The PersistenceUnitUtil interface provides access to utility methods that can be invoked on entities associated with the
 * persistence unit. The behavior is undefined if these methods are invoked on an entity instance that is not associated with the
 * persistence unit from whose entity manager factory this interface has been obtained.
 * @see JPA 2.0 specification
 * @author Florent Benoit
 * @since JPA 2.0 version.
 */
public interface PersistenceUnitUtil extends PersistenceUtil {

    /**
     * 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
     */
    boolean isLoaded(Object entity, String attributeName);

    /**
     * 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
     */
    boolean isLoaded(Object entity);

    /**
     * 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
     */
    Object getIdentifier(Object entity);
}