com.liferay.jbpm.util.QueryUtil.java Source code

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Here is the source code for com.liferay.jbpm.util.QueryUtil.java

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/**
 * Copyright (c) 2000-2009 Liferay, Inc. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package com.liferay.jbpm.util;

import com.liferay.portal.kernel.log.Log;
import com.liferay.portal.kernel.log.LogFactoryUtil;
import com.liferay.portal.kernel.util.OrderByComparator;
import com.liferay.portal.kernel.util.Randomizer;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.hibernate.Query;
import org.hibernate.ScrollableResults;
import org.hibernate.dialect.Dialect;

/**
 * <a href="QueryUtil.java.html"><b><i>View Source</i></b></a>
 *
 * @author Brian Wing Shun Chan
 *
 */
public class QueryUtil {

    public static final int ALL_POS = -1;

    public static Iterator<?> iterate(Query query, Dialect dialect, int begin, int end) {

        return list(query, dialect, begin, end).iterator();
    }

    public static List<?> list(Query query, Dialect dialect, int begin, int end) {

        if ((begin == ALL_POS) && (end == ALL_POS)) {
            return query.list();
        } else {
            if (dialect.supportsLimit()) {
                query.setMaxResults(end - begin);
                query.setFirstResult(begin);

                return query.list();
            } else {
                List<Object> list = new ArrayList<Object>();

                ScrollableResults sr = query.scroll();

                if (sr.first() && sr.scroll(begin)) {
                    for (int i = begin; i < end; i++) {
                        Object obj = sr.get(0);

                        list.add(obj);

                        if (!sr.next()) {
                            break;
                        }
                    }
                }

                return list;
            }
        }
    }

    public static List<?> randomList(Query query, Dialect dialect, int total, int num) {

        if ((total == 0) || (num == 0)) {
            return new ArrayList<Object>();
        }

        if (num >= total) {
            return list(query, dialect, ALL_POS, ALL_POS);
        }

        int[] scrollIds = Randomizer.getInstance().nextInt(total, num);

        List<Object> list = new ArrayList<Object>();

        ScrollableResults sr = query.scroll();

        for (int i = 0; i < scrollIds.length; i++) {
            if (sr.scroll(scrollIds[i])) {
                Object obj = sr.get(0);

                list.add(obj);

                sr.first();
            }
        }

        return list;
    }

    public static Comparable<?>[] getPrevAndNext(Query query, int count, OrderByComparator obc,
            Comparable<?> comparable) {

        int pos = count;
        int boundary = 0;

        Comparable<?>[] array = new Comparable[3];

        ScrollableResults sr = query.scroll();

        if (sr.first()) {
            while (true) {
                Object obj = sr.get(0);

                if (obj == null) {
                    if (_log.isWarnEnabled()) {
                        _log.warn("Object is null");
                    }

                    break;
                }

                Comparable<?> curComparable = (Comparable<?>) obj;

                int value = obc.compare(comparable, curComparable);

                if (_log.isDebugEnabled()) {
                    _log.debug("Comparison result is " + value);
                }

                if (value == 0) {
                    if (!comparable.equals(curComparable)) {
                        break;
                    }

                    array[1] = curComparable;

                    if (sr.previous()) {
                        array[0] = (Comparable<?>) sr.get(0);
                    }

                    sr.next();

                    if (sr.next()) {
                        array[2] = (Comparable<?>) sr.get(0);
                    }

                    break;
                }

                if (pos == 1) {
                    break;
                }

                pos = (int) Math.ceil(pos / 2.0);

                int scrollPos = pos;

                if (value < 0) {
                    scrollPos = scrollPos * -1;
                }

                boundary += scrollPos;

                if (boundary < 0) {
                    scrollPos = scrollPos + (boundary * -1) + 1;

                    boundary = 0;
                }

                if (boundary > count) {
                    scrollPos = scrollPos - (boundary - count);

                    boundary = scrollPos;
                }

                if (_log.isDebugEnabled()) {
                    _log.debug("Scroll " + scrollPos);
                }

                if (!sr.scroll(scrollPos)) {
                    if (value < 0) {
                        if (!sr.next()) {
                            break;
                        }
                    } else {
                        if (!sr.previous()) {
                            break;
                        }
                    }
                }
            }
        }

        return array;
    }

    private static Log _log = LogFactoryUtil.getLog(QueryUtil.class);

}