com.liferay.portal.kernel.dao.orm.QueryUtil.java Source code

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Here is the source code for com.liferay.portal.kernel.dao.orm.QueryUtil.java

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/**
 * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This library 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 Lesser General Public License for more
 * details.
 */

package com.liferay.portal.kernel.dao.orm;

import com.liferay.portal.kernel.dao.db.DB;
import com.liferay.portal.kernel.dao.db.DBManagerUtil;
import com.liferay.portal.kernel.log.Log;
import com.liferay.portal.kernel.log.LogFactoryUtil;
import com.liferay.portal.kernel.security.RandomUtil;

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

/**
 * @author Brian Wing Shun Chan
 */
public class QueryUtil {

    public static final int ALL_POS = -1;

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

        return iterate(query, dialect, start, end, true);
    }

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

        List<?> list = list(query, dialect, start, end);

        return list.iterator();
    }

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

        return list(query, dialect, start, end, true);
    }

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

        if ((start == ALL_POS) && (end == ALL_POS)) {
            return query.list(unmodifiable);
        }

        if (start < 0) {
            start = 0;
        }

        if (end < start) {
            end = start;
        }

        if (start == end) {
            if (unmodifiable) {
                return Collections.emptyList();
            }

            return new ArrayList<>();
        }

        if (dialect.supportsLimit()) {
            query.setMaxResults(end - start);
            query.setFirstResult(start);

            return query.list(unmodifiable);
        }

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

        DB db = DBManagerUtil.getDB();

        if (!db.isSupportsScrollableResults()) {
            if (_log.isWarnEnabled()) {
                _log.warn("Database does not support scrollable results");
            }

            return list;
        }

        ScrollableResults sr = query.scroll();

        if (sr.first() && sr.scroll(start)) {
            for (int i = start; i < end; i++) {
                Object[] array = sr.get();

                if (array.length == 1) {
                    list.add(array[0]);
                } else {
                    list.add(array);
                }

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

        if (unmodifiable) {
            return Collections.unmodifiableList(list);
        }

        return list;
    }

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

        return randomList(query, dialect, total, num, true);
    }

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

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

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

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

        DB db = DBManagerUtil.getDB();

        if (!db.isSupportsScrollableResults()) {
            if (_log.isWarnEnabled()) {
                _log.warn("Database does not support scrollable results");
            }

            return list;
        }

        ScrollableResults sr = query.scroll();

        int[] scrollIds = RandomUtil.nextInts(total, num);

        for (int scrollId : scrollIds) {
            if (sr.scroll(scrollId)) {
                Object[] array = sr.get();

                if (array.length == 1) {
                    list.add(array[0]);
                } else {
                    list.add(array);
                }

                sr.first();
            }
        }

        if (unmodifiable) {
            return Collections.unmodifiableList(list);
        }

        return list;
    }

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

}