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}