PersistenceUnitUtil.java

/**
 * Copyright (C) 2020 Czech Technical University in Prague
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details. You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package cz.cvut.kbss.jopa.model;

/**
 * Utility interface between the application and the persistence provider managing the persistence unit.
 * <p>
 * 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 {

    /**
     * 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.
     * <p>
     * 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 {@code FetchType.EAGER} has been specified have been loaded.
     * <p>
     * The {@link #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 instance 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);
}