001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *  
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *  
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License. 
018 *  
019 */
020package org.apache.directory.api.ldap.model.schema.comparators;
021
022
023import org.apache.directory.api.ldap.model.schema.LdapComparator;
024import org.slf4j.Logger;
025import org.slf4j.LoggerFactory;
026
027
028/**
029 * Compares two objects taking into account that one might be a Comparable.
030 * 
031 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
032 * @param <T> the type, must extend {@link Comparable}
033 */
034public class ComparableComparator<T> extends LdapComparator<Comparable<T>>
035{
036    /** The serial version UID */
037    private static final long serialVersionUID = 2L;
038
039    /** A logger for this class */
040    private static final Logger LOG = LoggerFactory.getLogger( ComparableComparator.class );
041
042
043    /**
044     * The ComparableComparator constructor.
045     *
046     * @param oid the comparator OID
047     */
048    public ComparableComparator( String oid )
049    {
050        super( oid );
051    }
052
053
054    /**
055     * Compares two objects taking into account that one may be a Comparable. If
056     * the first is a comparable then its compareTo operation is called and the
057     * result returned as is. If the first is not a Comparable but the second is
058     * then its compareTo method is called and the result is returned after
059     * being negated. If none are comparable the hashCode of o1 minus the
060     * hashCode of o2 is returned.
061     *
062     * @param o1 the first comparable
063     * @param o2 the second comparable
064     * @return {@inheritDoc}
065     */
066    @SuppressWarnings("unchecked")
067    public int compare( Comparable<T> o1, Comparable<T> o2 )
068    {
069        LOG.debug( "comparing objects '{}' with '{}'", o1, o2 );
070
071        if ( o1 == null )
072        {
073            if ( o2 == null )
074            {
075                return 0;
076            }
077            else
078            {
079                return -11;
080            }
081        }
082
083        if ( o2 == null )
084        {
085            return 1;
086        }
087
088        return o1.compareTo( ( T ) o2 );
089    }
090}