001 /* 002 * Copyright (C) 2003-2009 eXo Platform SAS. 003 * 004 * This is free software; you can redistribute it and/or modify it 005 * under the terms of the GNU Lesser General Public License as 006 * published by the Free Software Foundation; either version 2.1 of 007 * the License, or (at your option) any later version. 008 * 009 * This software is distributed in the hope that it will be useful, 010 * but WITHOUT ANY WARRANTY; without even the implied warranty of 011 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 012 * Lesser General Public License for more details. 013 * 014 * You should have received a copy of the GNU Lesser General Public 015 * License along with this software; if not, write to the Free 016 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 017 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 018 */ 019 package org.crsh.util; 020 021 import java.util.concurrent.*; 022 import java.util.concurrent.locks.Lock; 023 import java.util.concurrent.locks.ReentrantLock; 024 025 /** 026 * @author <a href="mailto:julien.viet@exoplatform.com">Julien Viet</a> 027 */ 028 public class LatchedFuture<V> implements Future<V> { 029 030 /** . */ 031 private V value = null; 032 033 /** . */ 034 private final CountDownLatch latch = new CountDownLatch(1); 035 036 /** . */ 037 private final Lock lock = new ReentrantLock(); 038 039 /** The optional listener. */ 040 private FutureListener<V> listener; 041 042 public LatchedFuture() { 043 } 044 045 public LatchedFuture(V value) { 046 set(value); 047 } 048 049 public boolean cancel(boolean b) { 050 return false; 051 } 052 053 public boolean isCancelled() { 054 return false; 055 } 056 057 public boolean isDone() { 058 return latch.getCount() == 0; 059 } 060 061 public V get() throws InterruptedException, ExecutionException { 062 latch.await(); 063 return value; 064 } 065 066 public V get(long l, TimeUnit timeUnit) throws InterruptedException, ExecutionException, TimeoutException { 067 latch.await(l, timeUnit); 068 return value; 069 } 070 071 public void addListener(FutureListener<V> listener) { 072 if (listener == null) { 073 throw new NullPointerException(); 074 } 075 lock.lock(); 076 try { 077 078 // Avoid double init 079 if (this.listener != null) { 080 throw new IllegalStateException(); 081 } 082 083 // Set state 084 this.listener = listener; 085 086 // 087 if (latch.getCount() == 0) { 088 listener.completed(value); 089 } 090 091 // 092 } finally { 093 lock.unlock(); 094 } 095 } 096 097 public void set(V value) { 098 lock.lock(); 099 try { 100 if (latch.getCount() > 0) { 101 this.value = value; 102 latch.countDown(); 103 if (listener != null) { 104 listener.completed(value); 105 } 106 } else { 107 throw new IllegalStateException(); 108 } 109 } finally { 110 lock.unlock(); 111 } 112 } 113 }