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 }