org.structr.common.PagingHelper.java Source code

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Here is the source code for org.structr.common.PagingHelper.java

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/**
 * Copyright (C) 2010-2016 Structr GmbH
 *
 * This file is part of Structr <http://structr.org>.
 *
 * Structr 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.
 *
 * Structr 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 Structr.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.structr.common;

import java.util.Collections;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.commons.lang3.StringUtils;
import org.structr.core.GraphObject;
import org.structr.core.Result;

//~--- classes ----------------------------------------------------------------

/**
 * Utility for paging
 *
 *
 */
public class PagingHelper {

    private static final Logger logger = Logger.getLogger(PagingHelper.class.getName());

    //~--- methods --------------------------------------------------------

    /**
     * Return a single page of the list with the given paging parameters.
     *
     * @param list
     * @param pageSize
     * @param page
     * @param offsetId
     * @return subList
     */
    public static List<? extends GraphObject> subList(final List<? extends GraphObject> list, int pageSize,
            int page, String offsetId) {

        if (pageSize <= 0 || page == 0) {

            return Collections.EMPTY_LIST;
        }

        int size = list.size();
        int fromIndex;
        int toIndex;
        if (StringUtils.isNotBlank(offsetId)) {

            int offsetIndex = 0;
            int i = 0;
            for (GraphObject obj : list) {
                if (obj.getUuid().equals(offsetId)) {
                    offsetIndex = i;
                    break;
                } else {
                    i++;
                    continue;
                }
            }

            fromIndex = page > 0 ? offsetIndex : offsetIndex + (page * pageSize);

        } else {

            fromIndex = page > 0 ? (page - 1) * pageSize : size + (page * pageSize);

        }

        toIndex = fromIndex + pageSize;

        int finalFromIndex = Math.max(0, fromIndex);
        int finalToIndex = Math.min(size, Math.max(0, toIndex));

        // prevent fromIndex to be greater than toIndex
        if (finalFromIndex > finalToIndex) {
            finalFromIndex = finalToIndex;
        }

        try {
            return list.subList(finalFromIndex, finalToIndex);

        } catch (Throwable t) {

            logger.log(Level.WARNING,
                    "Invalid range for sublist in paging, pageSize {0}, page {1}, offsetId {2}: {3}",
                    new Object[] { pageSize, page, offsetId, t.getMessage() });
        }

        return Collections.EMPTY_LIST;

    }

    /**
     * Return a single page of the result with the given paging parameters.
     *
     * @param result
     * @param pageSize
     * @param page
     * @param offsetId
     * @return subResult
     */
    public static Result subResult(final Result result, int pageSize, int page, String offsetId) {

        if (pageSize <= 0 || page == 0) {

            return result;
        }

        int pageCount = getPageCount(result.getRawResultCount(), pageSize);

        if (pageCount > 0) {

            result.setPageCount(pageCount);
        }

        if (page > pageCount) {

            page = pageCount;
        }

        result.setPage(page);
        result.setPageSize(pageSize);

        return new Result(subList(result.getResults(), pageSize, page, offsetId), result.getResults().size(),
                result.isCollection(), result.isPrimitiveArray());

    }

    public static Result addPagingParameter(Result result, int pageSize, int page) {

        if (pageSize > 0 && pageSize < Integer.MAX_VALUE) {

            int pageCount = getPageCount(result.getRawResultCount(), pageSize);

            if (pageCount > 0) {

                result.setPageCount(pageCount);
            }

            result.setPage(page);
            result.setPageSize(pageSize);

        }

        return result;

    }

    //~--- get methods ----------------------------------------------------

    private static int getPageCount(int resultCount, int pageSize) {

        return (int) Math.rint(Math.ceil((double) resultCount / (double) pageSize));

    }

}