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/*************************************************************************
*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* Copyright 2000, 2010 Oracle and/or its affiliates.
*
* OpenOffice.org - a multi-platform office productivity suite
*
* This file is part of OpenOffice.org.
*
* OpenOffice.org is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 3
* only, as published by the Free Software Foundation.
*
* OpenOffice.org is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License version 3 for more details
* (a copy is included in the LICENSE file that accompanied this code).
*
* You should have received a copy of the GNU Lesser General Public License
* version 3 along with OpenOffice.org. If not, see
* <http://www.openoffice.org/license.html>
* for a copy of the LGPLv3 License.
*
************************************************************************/
package com.sun.star.lib.uno.helper;
import java.lang.ref.WeakReference;
import com.sun.star.uno.XAdapter;
import com.sun.star.uno.XReference;
import java.util.List;
import java.util.Collections;
import java.util.LinkedList;
/** An XAdapter implementation that holds a weak reference (java.lang.ref.WeakReference)
* to an object. Clients can register listener (com.sun.star.lang.XReference) which
* are notified when the the object (the one which is kept weak) is being finalized. That
* is, that object is being destroyed because there are not any hard references
* to it.
*/
public class WeakAdapter implements XAdapter
{
private final boolean DEBUG= false;
// references the XWeak implementation
private WeakReference m_weakRef;
// contains XReference objects registered by addReference
private List m_xreferenceList;
/**
*@param component the object that is to be held weak
*/
public WeakAdapter(Object component)
{
m_weakRef= new WeakReference(component);
m_xreferenceList= Collections.synchronizedList( new LinkedList());
}
/** Called by the XWeak implementation (WeakBase) when it is being finalized.
* It is only being called once.
* The registererd XReference listeners are notified. On notification they are
* to unregister themselves. The notification is thread-safe. However, it is possible
* to add a listener during the notification process, which will never receive a
* notification. To prevent this, one would have to synchronize this method with
* the addReference method. But this can result in deadlocks in a multithreaded
* environment.
*/
void referentDying()
{
//synchronized call
Object[] references= m_xreferenceList.toArray();
for (int i= references.length; i > 0; i--)
{
((XReference) references[i-1]).dispose();
}
}
/** Method of com.sun.star.uno.XAdapter. It is called to obtain a hard reference
* to the object which is kept weak by this instance.
* @return hard reference to the object
*/
public Object queryAdapted()
{
return m_weakRef.get();
}
/** Method of com.sun.star.uno.XAdapter. Called by clients to register listener which
* are notified when the weak object is dying.
*@param xReference a listener
*/
public void removeReference(XReference xReference)
{
m_xreferenceList.remove(xReference);
}
/** Method of com.sun.star.uno.XAdapter. Called by clients to unregister listeners.
*@param a listener
*/
public void addReference(XReference xReference)
{
m_xreferenceList.add(xReference);
}
}
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