001 /* 002 * JBoss DNA (http://www.jboss.org/dna) 003 * See the COPYRIGHT.txt file distributed with this work for information 004 * regarding copyright ownership. Some portions may be licensed 005 * to Red Hat, Inc. under one or more contributor license agreements. 006 * See the AUTHORS.txt file in the distribution for a full listing of 007 * individual contributors. 008 * 009 * Unless otherwise indicated, all code in JBoss DNA is licensed 010 * to you under the terms of the GNU Lesser General Public License as 011 * published by the Free Software Foundation; either version 2.1 of 012 * the License, or (at your option) any later version. 013 * 014 * JBoss DNA is distributed in the hope that it will be useful, 015 * but WITHOUT ANY WARRANTY; without even the implied warranty of 016 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 017 * Lesser General Public License for more details. 018 * 019 * You should have received a copy of the GNU Lesser General Public 020 * License along with this software; if not, write to the Free 021 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 022 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 023 */ 024 package org.jboss.dna.jcr.cache; 025 026 import java.util.UUID; 027 import net.jcip.annotations.Immutable; 028 import org.jboss.dna.graph.property.Name; 029 import org.jboss.dna.graph.property.Path; 030 031 /** 032 * The representation of a child node. This is an immutable representation of a child node within the collection of its siblings 033 * as the collection appeared at some point in time. This should be used as a guide to determine how long to hold onto references. 034 * <p> 035 * For example, adding and removing children may affect the {@link #getSnsIndex() same-name-sibling index} of the children, so 036 * these kinds of operations will result in the replacement of old ChildObject instances. Therefore, clients should generally find 037 * the ChildNode instances in a {@link Children} container, use the ChildNode objects quickly, then discard their references. 038 * </p> 039 * <p> 040 * There may be times when a client does wish to keep a representation of a ChildNode as it appeared at some moment in time, and 041 * so it may want to hold onto references to ChildNode objects for longer durations. This is fine, as long as it is understood 042 * that at some point the referenced ChildNode may no longer represent the current state. 043 * </p> 044 */ 045 @Immutable 046 public final class ChildNode { 047 048 private final UUID uuid; 049 private final Path.Segment segment; 050 051 public ChildNode( UUID uuid, 052 Path.Segment segment ) { 053 assert uuid != null; 054 assert segment != null; 055 this.uuid = uuid; 056 this.segment = segment; 057 } 058 059 /** 060 * Get the UUID of the node. 061 * 062 * @return the node's UUID; never null 063 */ 064 public UUID getUuid() { 065 return uuid; 066 } 067 068 /** 069 * Get the path segment for this node. 070 * 071 * @return the path segment; never null 072 */ 073 public Path.Segment getSegment() { 074 return segment; 075 } 076 077 /** 078 * Get the name of the node. 079 * 080 * @return the node's current name; never null 081 */ 082 public Name getName() { 083 return segment.getName(); 084 } 085 086 /** 087 * Get the same-name-sibling index of the node. 088 * 089 * @return the node's SNS index; always positive 090 */ 091 public int getSnsIndex() { 092 return segment.getIndex(); 093 } 094 095 /** 096 * {@inheritDoc} 097 * 098 * @see java.lang.Object#hashCode() 099 */ 100 @Override 101 public int hashCode() { 102 return uuid.hashCode(); 103 } 104 105 /** 106 * {@inheritDoc} 107 * 108 * @see java.lang.Object#equals(java.lang.Object) 109 */ 110 @Override 111 public boolean equals( Object obj ) { 112 if (obj == this) return true; 113 if (obj instanceof ChildNode) { 114 return this.uuid.equals(((ChildNode)obj).uuid); 115 } 116 return false; 117 } 118 119 /** 120 * {@inheritDoc} 121 * 122 * @see java.lang.Object#toString() 123 */ 124 @Override 125 public String toString() { 126 return uuid.toString() + " ( " + getSegment() + " )"; 127 } 128 129 /** 130 * Obtain a new instance that uses the same {@link #getUuid() UUID} but the supplied path segment. 131 * 132 * @param newSegment the new segment; may not be null 133 * @return the new instance; never null 134 */ 135 public ChildNode with( Path.Segment newSegment ) { 136 return new ChildNode(uuid, newSegment); 137 } 138 139 }