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    
015    package org.apache.hivemind.impl;
016    
017    import java.util.AbstractMap;
018    import java.util.Map;
019    import 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     */
029    public 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    }