001package org.eclipse.aether.util.listener; 002 003/* 004 * Licensed to the Apache Software Foundation (ASF) under one 005 * or more contributor license agreements. See the NOTICE file 006 * distributed with this work for additional information 007 * regarding copyright ownership. The ASF licenses this file 008 * to you under the Apache License, Version 2.0 (the 009 * "License"); you may not use this file except in compliance 010 * with the License. You may obtain a copy of the License at 011 * 012 * http://www.apache.org/licenses/LICENSE-2.0 013 * 014 * Unless required by applicable law or agreed to in writing, 015 * software distributed under the License is distributed on an 016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 017 * KIND, either express or implied. See the License for the 018 * specific language governing permissions and limitations 019 * under the License. 020 */ 021 022import java.util.Arrays; 023import java.util.Collection; 024import java.util.List; 025import java.util.concurrent.CopyOnWriteArrayList; 026 027import org.eclipse.aether.transfer.AbstractTransferListener; 028import org.eclipse.aether.transfer.TransferCancelledException; 029import org.eclipse.aether.transfer.TransferEvent; 030import org.eclipse.aether.transfer.TransferListener; 031 032/** 033 * A transfer listener that delegates to zero or more other listeners (multicast). The list of target listeners is 034 * thread-safe, i.e. target listeners can be added or removed by any thread at any time. 035 */ 036public final class ChainedTransferListener 037 extends AbstractTransferListener 038{ 039 040 private final List<TransferListener> listeners = new CopyOnWriteArrayList<>(); 041 042 /** 043 * Creates a new multicast listener that delegates to the specified listeners. In contrast to the constructor, this 044 * factory method will avoid creating an actual chained listener if one of the specified readers is actually 045 * {@code null}. 046 * 047 * @param listener1 The first listener, may be {@code null}. 048 * @param listener2 The second listener, may be {@code null}. 049 * @return The chained listener or {@code null} if no listener was supplied. 050 */ 051 public static TransferListener newInstance( TransferListener listener1, TransferListener listener2 ) 052 { 053 if ( listener1 == null ) 054 { 055 return listener2; 056 } 057 else if ( listener2 == null ) 058 { 059 return listener1; 060 } 061 return new ChainedTransferListener( listener1, listener2 ); 062 } 063 064 /** 065 * Creates a new multicast listener that delegates to the specified listeners. 066 * 067 * @param listeners The listeners to delegate to, may be {@code null} or empty. 068 */ 069 public ChainedTransferListener( TransferListener... listeners ) 070 { 071 if ( listeners != null ) 072 { 073 add( Arrays.asList( listeners ) ); 074 } 075 } 076 077 /** 078 * Creates a new multicast listener that delegates to the specified listeners. 079 * 080 * @param listeners The listeners to delegate to, may be {@code null} or empty. 081 */ 082 public ChainedTransferListener( Collection<? extends TransferListener> listeners ) 083 { 084 add( listeners ); 085 } 086 087 /** 088 * Adds the specified listeners to the end of the multicast chain. 089 * 090 * @param listeners The listeners to add, may be {@code null} or empty. 091 */ 092 public void add( Collection<? extends TransferListener> listeners ) 093 { 094 if ( listeners != null ) 095 { 096 for ( TransferListener listener : listeners ) 097 { 098 add( listener ); 099 } 100 } 101 } 102 103 /** 104 * Adds the specified listener to the end of the multicast chain. 105 * 106 * @param listener The listener to add, may be {@code null}. 107 */ 108 public void add( TransferListener listener ) 109 { 110 if ( listener != null ) 111 { 112 listeners.add( listener ); 113 } 114 } 115 116 /** 117 * Removes the specified listener from the multicast chain. Trying to remove a non-existing listener has no effect. 118 * 119 * @param listener The listener to remove, may be {@code null}. 120 */ 121 public void remove( TransferListener listener ) 122 { 123 if ( listener != null ) 124 { 125 listeners.remove( listener ); 126 } 127 } 128 129 @SuppressWarnings( "EmptyMethod" ) 130 protected void handleError( TransferEvent event, TransferListener listener, RuntimeException error ) 131 { 132 // default just swallows errors 133 } 134 135 @Override 136 public void transferInitiated( TransferEvent event ) 137 throws TransferCancelledException 138 { 139 for ( TransferListener listener : listeners ) 140 { 141 try 142 { 143 listener.transferInitiated( event ); 144 } 145 catch ( RuntimeException e ) 146 { 147 handleError( event, listener, e ); 148 } 149 } 150 } 151 152 @Override 153 public void transferStarted( TransferEvent event ) 154 throws TransferCancelledException 155 { 156 for ( TransferListener listener : listeners ) 157 { 158 try 159 { 160 listener.transferStarted( event ); 161 } 162 catch ( RuntimeException e ) 163 { 164 handleError( event, listener, e ); 165 } 166 } 167 } 168 169 @Override 170 public void transferProgressed( TransferEvent event ) 171 throws TransferCancelledException 172 { 173 for ( TransferListener listener : listeners ) 174 { 175 try 176 { 177 listener.transferProgressed( event ); 178 } 179 catch ( RuntimeException e ) 180 { 181 handleError( event, listener, e ); 182 } 183 } 184 } 185 186 @Override 187 public void transferCorrupted( TransferEvent event ) 188 throws TransferCancelledException 189 { 190 for ( TransferListener listener : listeners ) 191 { 192 try 193 { 194 listener.transferCorrupted( event ); 195 } 196 catch ( RuntimeException e ) 197 { 198 handleError( event, listener, e ); 199 } 200 } 201 } 202 203 @Override 204 public void transferSucceeded( TransferEvent event ) 205 { 206 for ( TransferListener listener : listeners ) 207 { 208 try 209 { 210 listener.transferSucceeded( event ); 211 } 212 catch ( RuntimeException e ) 213 { 214 handleError( event, listener, e ); 215 } 216 } 217 } 218 219 @Override 220 public void transferFailed( TransferEvent event ) 221 { 222 for ( TransferListener listener : listeners ) 223 { 224 try 225 { 226 listener.transferFailed( event ); 227 } 228 catch ( RuntimeException e ) 229 { 230 handleError( event, listener, e ); 231 } 232 } 233 } 234 235}