org.nuclos.common.collect.collectable.CollectableComparatorFactory.java Source code

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Here is the source code for org.nuclos.common.collect.collectable.CollectableComparatorFactory.java

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//Copyright (C) 2010  Novabit Informationssysteme GmbH
//
//This file is part of Nuclos.
//
//Nuclos is free software: you can redistribute it and/or modify
//it under the terms of the GNU Affero General Public License as published by
//the Free Software Foundation, either version 3 of the License, or
//(at your option) any later version.
//
//Nuclos 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 Affero General Public License for more details.
//
//You should have received a copy of the GNU Affero General Public License
//along with Nuclos.  If not, see <http://www.gnu.org/licenses/>.
package org.nuclos.common.collect.collectable;

import java.util.Comparator;

import org.apache.commons.lang.NullArgumentException;

import org.nuclos.common2.LangUtils;
import org.nuclos.common2.exception.CommonFatalException;
import org.nuclos.common.ApplicationProperties;

/**
 * Factory that creates a <code>Comparator</code> for Collectables.
 * <br>
 * <br>Created by Novabit Informationssysteme GmbH
 * <br>Please visit <a href="http://www.novabit.de">www.novabit.de</a>
 *
 * @author   <a href="mailto:Martin.Weber@novabit.de">Martin.Weber</a>
 * @version 01.00.00
 */
public class CollectableComparatorFactory<Clct extends Collectable> {

    private static CollectableComparatorFactory<?> singleton;

    protected CollectableComparatorFactory() {
    }

    public static synchronized CollectableComparatorFactory<?> getInstance() {
        if (singleton == null) {
            try {
                final String sClassName = LangUtils.defaultIfNull(
                        ApplicationProperties.getInstance().getCollectableComparatorFactoryClassName(),
                        CollectableComparatorFactory.class.getName());

                singleton = (CollectableComparatorFactory<?>) Class.forName(sClassName).newInstance();
            } catch (Exception ex) {
                throw new CommonFatalException("Cannot create CollectableComparatorFactory.", ex);
            }
        }
        return singleton;
    }

    /**
     * @param sEntityName
     * @param clctEntityField
     * @return comparator for given entity and entityfield
     * @precondition clctEntityField != null
     */
    public Comparator<Clct> newCollectableComparator(String sEntityName, CollectableEntityField clctEntityField) {
        if (clctEntityField == null) {
            throw new NullArgumentException("clctEntityField");
        }

        return new CollectableComparator<Clct>(clctEntityField);
    }

    /**
     * @return comparator that sorts by id field
     * @precondition clctEntityField != null
     */
    public Comparator<Clct> newCollectableIdComparator() {
        return new Comparator<Clct>() {

            @Override
            public int compare(Clct clct1, Clct clct2) {
                int result = 0;

                Object oId1 = clct1.getId();
                Object oId2 = clct2.getId();
                if (oId1 instanceof Comparable<?> && oId2 instanceof Comparable<?>) {
                    Comparable<Object> comp1 = (Comparable<Object>) oId1;
                    Comparable<Object> comp2 = (Comparable<Object>) oId2;
                    result = comp1 == null ? 1 : comp2 == null ? -1 : comp1.compareTo(oId2);
                }
                return result;
            }
        };
    }
}