1 /************************************************************** 2 * 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, 14 * software distributed under the License is distributed on an 15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 16 * KIND, either express or implied. See the License for the 17 * specific language governing permissions and limitations 18 * under the License. 19 * 20 *************************************************************/ 21 22 23 24 package com.sun.star.lib.uno.helper; 25 import java.lang.ref.WeakReference; 26 import com.sun.star.uno.XAdapter; 27 import com.sun.star.uno.XReference; 28 import java.util.List; 29 import java.util.Collections; 30 import java.util.LinkedList; 31 32 /** An XAdapter implementation that holds a weak reference (java.lang.ref.WeakReference) 33 * to an object. Clients can register listener (com.sun.star.lang.XReference) which 34 * are notified when the the object (the one which is kept weak) is being finalized. That 35 * is, that object is being destroyed because there are not any hard references 36 * to it. 37 */ 38 public class WeakAdapter implements XAdapter 39 { 40 private final boolean DEBUG= false; 41 // references the XWeak implementation 42 private WeakReference m_weakRef; 43 // contains XReference objects registered by addReference 44 private List m_xreferenceList; 45 46 /** 47 *@param component the object that is to be held weak 48 */ WeakAdapter(Object component)49 public WeakAdapter(Object component) 50 { 51 m_weakRef= new WeakReference(component); 52 m_xreferenceList= Collections.synchronizedList( new LinkedList()); 53 } 54 55 /** Called by the XWeak implementation (WeakBase) when it is being finalized. 56 * It is only being called once. 57 * The registererd XReference listeners are notified. On notification they are 58 * to unregister themselves. The notification is thread-safe. However, it is possible 59 * to add a listener during the notification process, which will never receive a 60 * notification. To prevent this, one would have to synchronize this method with 61 * the addReference method. But this can result in deadlocks in a multithreaded 62 * environment. 63 */ referentDying()64 void referentDying() 65 { 66 //synchronized call 67 Object[] references= m_xreferenceList.toArray(); 68 for (int i= references.length; i > 0; i--) 69 { 70 ((XReference) references[i-1]).dispose(); 71 } 72 } 73 74 /** Method of com.sun.star.uno.XAdapter. It is called to obtain a hard reference 75 * to the object which is kept weak by this instance. 76 * @return hard reference to the object 77 */ queryAdapted()78 public Object queryAdapted() 79 { 80 return m_weakRef.get(); 81 } 82 83 /** Method of com.sun.star.uno.XAdapter. Called by clients to register listener which 84 * are notified when the weak object is dying. 85 *@param xReference a listener 86 */ removeReference(XReference xReference)87 public void removeReference(XReference xReference) 88 { 89 m_xreferenceList.remove(xReference); 90 } 91 92 /** Method of com.sun.star.uno.XAdapter. Called by clients to unregister listeners. 93 *@param xReference listener 94 */ addReference(XReference xReference)95 public void addReference(XReference xReference) 96 { 97 m_xreferenceList.add(xReference); 98 } 99 } 100 101