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.shared.ldap.model.schema.comparators;
021
022
023import java.io.Serializable;
024
025import org.apache.directory.shared.ldap.model.schema.LdapComparator;
026import org.slf4j.Logger;
027import org.slf4j.LoggerFactory;
028
029
030/**
031 * A comparator for Strings.
032 * 
033 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
034 */
035public class StringComparator extends LdapComparator<String> implements Serializable
036{
037    /** The serial version UID */
038    private static final long serialVersionUID = 2L;
039
040
041    /** A logger for this class */
042    private static final Logger LOG = LoggerFactory.getLogger( StringComparator.class );
043
044
045    /**
046     * The StringComparator constructor. Its OID is the StringMatch matching
047     * rule OID.
048     */
049    public StringComparator( String oid )
050    {
051        super( oid );
052    }
053
054
055    /**
056     * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
057     */
058    @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "ES_COMPARING_PARAMETER_STRING_WITH_EQ",
059                justification ="false positive")
060    public int compare( String s1, String s2 )
061    {
062        LOG.debug( "comparing String objects '{}' with '{}'", s1, s2 );
063
064        if ( s1 == s2 )
065        {
066            return 0;
067        }
068
069        // -------------------------------------------------------------------
070        // Handle some basis cases
071        // -------------------------------------------------------------------
072        if ( s1 == null )
073        {
074            return ( s2 == null ) ? 0 : -1;
075        }
076
077        if ( s2 == null )
078        {
079            return 1;
080        }
081
082        return s1.compareTo( s2 );
083    }
084}