001// Copyright 2004, 2005 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry.record;
016
017import org.apache.hivemind.util.Defense;
018
019/**
020 * Used to identify a property change.
021 * 
022 * @author Howard Lewis Ship
023 */
024
025public class ChangeKey
026{
027    private int _hashCode = -1;
028
029    private String _componentPath;
030
031    private String _propertyName;
032
033    public ChangeKey(String componentPath, String propertyName)
034    {
035        Defense.notNull(propertyName, "propertyName");
036
037        _componentPath = componentPath;
038        _propertyName = propertyName;
039    }
040
041    public boolean equals(Object object)
042    {
043        if (object == null)
044            return false;
045
046        if (this == object)
047            return true;
048
049        if (!(object instanceof ChangeKey))
050            return false;
051
052        ChangeKey other = (ChangeKey) object;
053
054        return same(_propertyName, other._propertyName)
055                && same(_componentPath, other._componentPath);
056    }
057
058    private boolean same(String s1, String s2)
059    {
060        return s1 == s2 || (s1 != null && s1.equals(s2));
061    }
062
063    public String getComponentPath()
064    {
065        return _componentPath;
066    }
067
068    public String getPropertyName()
069    {
070        return _propertyName;
071    }
072
073    /**
074     * Returns a hash code computed from the property name and component path.
075     */
076
077    public int hashCode()
078    {
079        if (_hashCode == -1)
080        {
081            _hashCode = 31 * 27 + _propertyName.hashCode();
082
083            if (_componentPath != null)
084                _hashCode = 31 * _hashCode + _componentPath.hashCode();
085        }
086
087        return _hashCode;
088    }
089}