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.hivemind.impl;
016
017import java.util.AbstractMap;
018import java.util.Map;
019import java.util.Set;
020
021/**
022 * Implements a {@link java.util.Map} as a proxy to an actual map of elements, provided by an
023 * extension point. The proxy is unmodifiable and will work with the extension point to generate the
024 * real map of elements in a just-in-time manner.
025 * 
026 * @author Knut Wannheden
027 * @since 1.1
028 */
029public final class ElementsInnerProxyMap extends AbstractMap
030{
031    private Map _inner;
032
033    private ConfigurationPointImpl _point;
034
035    private ElementsProxyMap _outer;
036
037    ElementsInnerProxyMap(ConfigurationPointImpl point, ElementsProxyMap outer)
038    {
039        _point = point;
040        _outer = outer;
041
042        _outer.setInner(this);
043    }
044
045    public Set entrySet()
046    {
047        return inner().entrySet();
048    }
049
050    private synchronized Map inner()
051    {
052        if (_inner == null)
053        {
054            _inner = _point.constructMapElements();
055
056            // Replace ourselves in the outer proxy with the actual list.
057            _outer.setInner(_inner);
058        }
059
060        return _inner;
061    }
062
063    public boolean equals(Object o)
064    {
065        if (this == o)
066            return true;
067
068        if (o == null)
069            return false;
070
071        return inner().equals(o);
072    }
073
074    public int hashCode()
075    {
076        return inner().hashCode();
077    }
078
079    public synchronized String toString()
080    {
081        if (_inner != null)
082            return _inner.toString();
083
084        return "<Element Map Proxy for " + _point.getExtensionPointId() + ">";
085    }
086
087}