1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.directory.api.ldap.model.schema.comparators;
21
22
23 import org.apache.directory.api.i18n.I18n;
24 import org.apache.directory.api.ldap.model.schema.LdapComparator;
25 import org.slf4j.Logger;
26 import org.slf4j.LoggerFactory;
27
28
29 /**
30 * Compares two objects taking into account that one might be a Comparable.
31 *
32 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
33 * @param <T> the type, must extend {@link Comparable}
34 */
35 public class ComparableComparator<T> extends LdapComparator<Comparable<T>>
36 {
37 /** The serial version UID */
38 private static final long serialVersionUID = 2L;
39
40 /** A logger for this class */
41 private static final Logger LOG = LoggerFactory.getLogger( ComparableComparator.class );
42
43
44 /**
45 * The ComparableComparator constructor.
46 *
47 * @param oid the comparator OID
48 */
49 public ComparableComparator( String oid )
50 {
51 super( oid );
52 }
53
54
55 /**
56 * Compares two objects taking into account that one may be a Comparable. If
57 * the first is a comparable then its compareTo operation is called and the
58 * result returned as is. If the first is not a Comparable but the second is
59 * then its compareTo method is called and the result is returned after
60 * being negated. If none are comparable the hashCode of o1 minus the
61 * hashCode of o2 is returned.
62 *
63 * @param o1 the first comparable
64 * @param o2 the second comparable
65 * @return {@inheritDoc}
66 */
67 @SuppressWarnings("unchecked")
68 public int compare( Comparable<T> o1, Comparable<T> o2 )
69 {
70 LOG.debug( "comparing objects '{}' with '{}'", o1, o2 );
71
72 if ( ( o1 == null ) && ( o2 == null ) )
73 {
74 return 0;
75 }
76
77 if ( o1 instanceof Comparable<?> )
78 {
79 if ( o2 == null )
80 {
81 return -1;
82 }
83 else
84 {
85 // TODO: check type parameter
86 return o1.compareTo( ( T ) o2 );
87 }
88 }
89
90 if ( o2 == null )
91 {
92 return 1;
93 }
94 else if ( o2 instanceof Comparable<?> )
95 {
96 if ( o1 == null )
97 {
98 return -1;
99 }
100 else
101 {
102 // TODO: check type parameter
103 return -o2.compareTo( ( T ) o1 );
104 }
105 }
106
107 // before https://issues.apache.org/jira/browse/DIRSERVER-928 it was
108 // return o1.hashCode() - o2.hashCode();
109
110 // now we will blow a stack trace if none of the objects are Comparable
111 throw new IllegalArgumentException( I18n.err( I18n.ERR_04217, o1, o2 ) );
112 }
113 }