ManagedTypeValueMerger.java

/**
 * Copyright (C) 2022 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.sessions.merge;

import cz.cvut.kbss.jopa.model.descriptors.Descriptor;
import cz.cvut.kbss.jopa.sessions.ChangeRecord;
import cz.cvut.kbss.jopa.sessions.UnitOfWorkImpl;
import cz.cvut.kbss.jopa.utils.EntityPropertiesUtils;

class ManagedTypeValueMerger implements ValueMerger {

    private final UnitOfWorkImpl uow;

    ManagedTypeValueMerger(UnitOfWorkImpl uow) {
        this.uow = uow;
    }

    @Override
    public void mergeValue(Object target, ChangeRecord changeRecord, Descriptor attributeDescriptor) {
        final Object mergedValue = changeRecord.getNewValue();
        final Object toSet = getValueToSet(mergedValue, attributeDescriptor);
        EntityPropertiesUtils.setFieldValue(changeRecord.getAttribute().getJavaField(), target, toSet);
        // Replace the value in the change record as the mergedValue may not have been managed
        changeRecord.setNewValue(toSet);
    }

    Object getValueToSet(Object mergedValue, Descriptor descriptor) {
        if (mergedValue == null) {
            return null;
        }
        final Object identifier = EntityPropertiesUtils.getIdentifier(mergedValue, uow.getMetamodel());
        if (identifier == null) {
            return mergedValue;
        }
        final Class<?> type = mergedValue.getClass();
        final Object managedInstance = uow.readObject(type, identifier, descriptor);
        // If the object cannot be found, it is a new one (not yet registered), which we can assign directly
        return managedInstance != null ? managedInstance : mergedValue;
    }
}