mapcomparator.java

国外的一套开源CRM

/*
 * $Id: MapComparator.java,v 1.2 2003/11/30 18:02:16 jonesde Exp $
 *
 *  Copyright (c) 2001, 2002 The Open For Business Project - www.ofbiz.org
 *
 *  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 org.ofbiz.base.util;

import java.sql.Timestamp;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 * MapComparator.java
 * 
 * @author     <a href="mailto:[e-mail]">Andy Zeneski</a>
 * @author     <a href="mailto:[e-mail]">David E. Jones</a>
 * @version    $Revision: 1.2 $
 * @since      2.0
 */
public class MapComparator implements Comparator {
    
    public static final String module = MapComparator.class.getName();
    
    private List keys;

    /**
     * Method MapComparator.
     * @param keys List of Map keys to sort on
     */
    public MapComparator(List keys) {
        this.keys = keys;
    }

    /**
     * @see java.lang.Object#equals(java.lang.Object)
     */
    public boolean equals(Object obj) {
        return obj.equals(this);
    }

    /**
     * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
     */
    public int compare(Object obj1, Object obj2) {
        Map map1, map2;
        try {
            map1 = (Map) obj1;
            map2 = (Map) obj2;
        } catch (ClassCastException e) {
            throw new IllegalArgumentException("Objects not from the Map interface");
        }

        if (keys == null || keys.size() < 1) {
            throw new IllegalArgumentException("No sort fields defined");
        }

        Iterator i = keys.iterator();
        while (i.hasNext()) {
            // if false will be descending, ie reverse order
            boolean ascending = true;
            Object key = i.next();
            if (key instanceof String) {
                String keyStr = (String) key;
                if (keyStr.charAt(0) == '-') {
                    ascending = false;
                    key = keyStr.substring(1);
                } else if (keyStr.charAt(0) == '+') {
                    ascending = true;
                    key = keyStr.substring(1);
                }
            }
            
            Object o1 = map1.get(key);
            Object o2 = map2.get(key);
            if (o1 == null && o2 == null) {
                continue;
            }
            
            int compareResult = 0;
            if (o1 != null && o2 == null) {
                compareResult = -1;
            }
            if (o1 == null && o2 != null) {
                compareResult = 1;
            }
            
            if (compareResult == 0) {
                try {
                    // the map values in question MUST implement the Comparable interface, if not we'll throw an exception
                    Comparable comp1 = (Comparable) o1;
                    Comparable comp2 = (Comparable) o2;
                    compareResult = comp1.compareTo(comp2);
                } catch (Exception e) {
                    String errorMessage = "Error sorting list of Maps: " + e.toString();
                    Debug.logError(e, errorMessage, module);
                    throw new RuntimeException(errorMessage);
                }
            }

            // if zero they are equal, so we carry on to the next key to try and find a difference
            if (compareResult != 0) {
                if (ascending) {
                    return compareResult;
                } else {
                    return -compareResult;
                }
            }
        }
        
        // none of them were different, so they are equal
        return 0;
    }
}