ListPageFetcher.java example

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/*
 * NOTE: This copyright does *not* cover user programs that use HQ
 * program services by normal system calls through the application
 * program interfaces provided as part of the Hyperic Plug-in Development
 * Kit or the Hyperic Client Development Kit - this is merely considered
 * normal use of the program, and does *not* fall under the heading of
 * "derived work".
 * 
 * Copyright (C) [2004, 2005, 2006], Hyperic, Inc.
 * This file is part of HQ.
 * 
 * HQ is free software; you can redistribute it and/or modify
 * it under the terms version 2 of the GNU General Public License as
 * published by the Free Software Foundation. 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA.
 */

package org.hyperic.util.pager;

import org.hyperic.util.math.MathUtil;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.ListIterator;

/**
 * A PageFetcher which works with a pre-fetched list as the 
 * data backing the fetcher.
 */

public class ListPageFetcher 
    extends PageFetcher
{
    private List data;
    private int  sortOrder;

    public ListPageFetcher(List data){
        super();
        this.data      = data;
        this.sortOrder = PageControl.SORT_UNSORTED;
    }

    public PageList getPage(PageControl control){
        PageList res = new PageList();
        int startIdx, curIdx, endIdx;

        if(this.data.size() == 0){
            return new PageList();
        }

        this.ensureSortOrder(control);
        res.setTotalSize(this.data.size());

        startIdx = MathUtil.clamp(control.getPageEntityIndex(), 0, 
                              this.data.size() - 1);
        curIdx   = startIdx;

        if(control.getPagesize() == PageControl.SIZE_UNLIMITED){
            endIdx = this.data.size();
        } else {
            endIdx = MathUtil.clamp(startIdx + control.getPagesize(), startIdx,
                                this.data.size());
        }

        for(ListIterator i=this.data.listIterator(startIdx); 
            i.hasNext() && curIdx < endIdx; 
            curIdx++)
        {
            res.add(i.next());
        }
        return res;
    }

    private class DescSorter implements Comparator {
        public int compare(Object o1, Object o2){
            return -((Comparable)o1).compareTo((Comparable)o2);
        }

        public boolean equals(Object other){
            return false;
        }
    }

    private void ensureSortOrder(PageControl control){
        if(control.getSortorder() == this.sortOrder)
            return;
        
        this.sortOrder = control.getSortorder();
        if(this.sortOrder == PageControl.SORT_UNSORTED){
            return;
        } else if(this.sortOrder == PageControl.SORT_ASC){
            Collections.sort(data);
        } else if(this.sortOrder == PageControl.SORT_DESC){
            Collections.sort(data, new DescSorter());
        } else {
            throw new IllegalStateException("Unknown control sorting type: " +
                                            this.sortOrder);
        }
    }
}