1 /** 2 * This file Copyright (c) 2011 Magnolia International 3 * Ltd. (http://www.magnolia-cms.com). All rights reserved. 4 * 5 * 6 * This file is dual-licensed under both the Magnolia 7 * Network Agreement and the GNU General Public License. 8 * You may elect to use one or the other of these licenses. 9 * 10 * This file is distributed in the hope that it will be 11 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the 12 * implied warranty of MERCHANTABILITY or FITNESS FOR A 13 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT. 14 * Redistribution, except as permitted by whichever of the GPL 15 * or MNA you select, is prohibited. 16 * 17 * 1. For the GPL license (GPL), you can redistribute and/or 18 * modify this file under the terms of the GNU General 19 * Public License, Version 3, as published by the Free Software 20 * Foundation. You should have received a copy of the GNU 21 * General Public License, Version 3 along with this program; 22 * if not, write to the Free Software Foundation, Inc., 51 23 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 24 * 25 * 2. For the Magnolia Network Agreement (MNA), this file 26 * and the accompanying materials are made available under the 27 * terms of the MNA which accompanies this distribution, and 28 * is available at http://www.magnolia-cms.com/mna.html 29 * 30 * Any modifications to this file must keep this entire header 31 * intact. 32 * 33 */ 34 package info.magnolia.registry; 35 36 import org.apache.commons.lang.StringUtils; 37 38 import java.util.ArrayList; 39 import java.util.Collection; 40 import java.util.HashMap; 41 import java.util.HashSet; 42 import java.util.Map; 43 import java.util.Set; 44 45 /** 46 * Thread safe map intended to be used for registries. Provides an atomic operation <code>removeAndPutAll</code> that is 47 * used to remove a set of previously added values before adding a collection of new ones. Read operations are blocked 48 * until it completes guaranteeing proper visibility. 49 * <p/> 50 * It is common for entities in registries to also hold their identifier. The method <code>keyFormValue</code> can be 51 * overridden to get the identifier from the value. This removes the need to package a set of entities that should be 52 * added in a Map before calling {@link #removeAndPutAll(java.util.Collection, java.util.Map)}. 53 * 54 * @param <K> the type of keys maintained by this map 55 * @param <V> the type of mapped values 56 * @version $Id$ 57 */ 58 public class RegistryMap<K, V> { 59 60 private final Map<K, V> map = new HashMap<K, V>(); 61 62 public synchronized V get(K key) { 63 return map.get(key); 64 } 65 66 public synchronized V getRequired(K key) throws RegistrationException { 67 V value = map.get(key); 68 if (value == null) { 69 throw new RegistrationException("Entry for [" + key + "] not found in registry, available entries are: " + 70 (map.isEmpty() ? "<none>" : StringUtils.join(map.keySet(), ", "))); 71 } 72 return value; 73 } 74 75 public synchronized void put(K key, V value) { 76 map.put(key, value); 77 } 78 79 public synchronized void put(V value) { 80 map.put(keyFromValue(value), value); 81 } 82 83 public synchronized void remove(K key) { 84 map.remove(key); 85 } 86 87 public synchronized void removeAndPutAll(Collection<K> toRemove, Map<K, V> toPut) { 88 // Fail early if the keyFromValue method hasn't been overridden 89 if (!toPut.isEmpty()) { 90 keyFromValue(toPut.values().iterator().next()); 91 } 92 for (K key : toRemove) { 93 map.remove(key); 94 } 95 map.putAll(toPut); 96 } 97 98 public synchronized Set<K> removeAndPutAll(Collection<K> toRemove, Collection<V> toPut) { 99 if (!toPut.isEmpty()) { 100 keyFromValue(toPut.iterator().next()); 101 } 102 for (K key : toRemove) { 103 map.remove(key); 104 } 105 HashSet<K> keys = new HashSet<K>(); 106 for (V value : toPut) { 107 K key = keyFromValue(value); 108 map.put(key, value); 109 keys.add(key); 110 } 111 return keys; 112 } 113 114 public synchronized Collection<K> keySet() { 115 return new ArrayList<K>(map.keySet()); 116 } 117 118 public synchronized Collection<V> values() { 119 return new ArrayList<V>(map.values()); 120 } 121 122 protected K keyFromValue(V value) { 123 throw new UnsupportedOperationException("keyFromValue"); 124 } 125 }