382 lines
12 KiB
Java
382 lines
12 KiB
Java
/* java.beans.beancontext.BeanContextChildSupport
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Copyright (C) 1999 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.beans.beancontext;
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import java.beans.PropertyChangeEvent;
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import java.beans.PropertyChangeListener;
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import java.beans.PropertyChangeSupport;
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import java.beans.PropertyVetoException;
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import java.beans.VetoableChangeListener;
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import java.beans.VetoableChangeSupport;
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import java.io.Serializable;
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/**
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* Support for creating a <code>BeanContextChild</code>.
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* This class contains the most common implementations of the methods in
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* the <code>BeanContextChild</code>
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*
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* @specnote This class is not very well specified. I had to "fill in the
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* blanks" in most places with what I thought was reasonable
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* behavior. If there are problems, let me know.
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*
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* @author John Keiser
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* @since 1.2
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* @see java.beans.beancontext.BeanContextChild
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*/
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public class BeanContextChildSupport
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implements BeanContextChild, BeanContextServicesListener, Serializable
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{
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static final long serialVersionUID = 6328947014421475877L;
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/**
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* The peer on which to perform <code>set</code> actions.
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* This is here so that this class can be used as a peer.
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* <P>
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*
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* When extending this class, this variable will be set to
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* <code>this</code>.
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*/
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public BeanContextChild beanContextChildPeer;
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/**
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* The parent <code>BeanContext</code>.
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*/
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protected transient BeanContext beanContext;
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/**
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* If <code>setBeanContext()</code> was vetoed once before, this
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* is set to <code>true</code> so that the next time, vetoes will
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* be ignored.
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*/
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protected transient boolean rejectedSetBCOnce;
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/**
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* Listeners are registered here and events are fired through here.
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*/
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protected PropertyChangeSupport pcSupport;
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/**
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* Listeners are registered here and events are fired through here.
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*/
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protected VetoableChangeSupport vcSupport;
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/**
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* Create a new <code>BeanContextChildSupport</code> with itself as the peer.
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* This is meant to be used when you subclass
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* <code>BeanContextChildSupport</code> to create your child.
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*/
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public BeanContextChildSupport()
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{
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this (null);
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}
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/**
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* Create a new <code>BeanContextChildSupport</code> with the specified peer.
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* @param peer the peer to use, or <code>null</code> to specify
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* <code>this</code>.
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*/
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public BeanContextChildSupport (BeanContextChild peer)
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{
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if (peer == null)
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{
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peer = this;
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}
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beanContextChildPeer = peer;
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pcSupport = new PropertyChangeSupport (peer);
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vcSupport = new VetoableChangeSupport (peer);
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}
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/**
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* Set the parent <code>BeanContext</code>.
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* <P>
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*
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* When this Object is being added to a new BeanContext or moved
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* from an old one, a non-null value will be passed in.
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* <P>
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*
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* When this Object is being removed from the current
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* <code>BeanContext</code>, <code>setBeanContext()</code> will
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* receive the parameter <code>null</code>.
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* <P>
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*
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* Order of events:
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* <OL>
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* <LI>
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* If the new <code>BeanContext</code> is the same as the old
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* one, nothing happens.
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* </LI>
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* <LI>
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* If the change has not been rejected or vetoed before, call
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* <code>validatePendingSetBeanContext()</code>. If this call
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* returns <code>false</code>, the change is rejected and a
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* <code>PropertyVetoException</code> is thrown.
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* </LI>
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* <LI>
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* If the change has not been rejected or vetoed before,
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* <code>VetoableChangeEvent</code>s are fired with the name
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* <code>"beanContext"</code>, using the
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* <code>fireVetoableChange()</code> method. If a veto
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* occurs, reversion events are fired using the same method,
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* the change is rejected, and the veto is rethrown.
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* </LI>
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* <LI>
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* <code>releaseBeanContextResources()</code> is called.
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* </LI>
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* <LI>
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* The change is made.
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* </LI>
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* <LI>
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* <code>PropertyChangeEvent</code>s are fired using the
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* <code>firePropertyChange()</code> method.
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* </LI>
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* <LI>
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* <code>initializeBeanContextResources()</code> is called.
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* </LI>
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* </OL>
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* <P>
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*
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* @param newBeanContext the new parent for the
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* <code>BeanContextChild</code>, or <code>null</code> to
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* signify removal from a tree.
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* @exception PropertyVetoException if the
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* <code>BeanContextChild</code> implementor does not
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* wish to have its parent changed.
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*/
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public void setBeanContext(BeanContext newBeanContext)
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throws PropertyVetoException
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{
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synchronized (beanContextChildPeer)
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{
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if (newBeanContext == beanContext)
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return;
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if (!rejectedSetBCOnce)
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{
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if (!validatePendingSetBeanContext (newBeanContext))
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{
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rejectedSetBCOnce = true;
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throw new PropertyVetoException ("validatePendingSetBeanContext() rejected change",
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new PropertyChangeEvent(beanContextChildPeer, "beanContext", beanContext, newBeanContext));
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}
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try
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{
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fireVetoableChange ("beanContext", beanContext, newBeanContext);
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}
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catch (PropertyVetoException e)
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{
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rejectedSetBCOnce = true;
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throw e;
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}
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}
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releaseBeanContextResources ();
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beanContext = newBeanContext;
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rejectedSetBCOnce = false;
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firePropertyChange ("beanContext", beanContext, newBeanContext);
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initializeBeanContextResources ();
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}
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}
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/**
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* Get the parent <code>BeanContext</code>.
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* @return the parent <code>BeanContext</code>.
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*/
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public BeanContext getBeanContext()
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{
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return beanContext;
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}
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/**
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* Get the peer (or <code>this</code> if there is no peer).
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* @return the peer, or <code>this</code> if there is no peer.
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*/
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public BeanContextChild getBeanContextChildPeer() {
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return beanContextChildPeer;
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}
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/**
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* Determine whether there is a peer.
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* This is true iff <code>getBeanContextChildPeer() == this</code>.
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* @return whether there is a peer.
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*/
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public boolean isDelegated() {
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return beanContextChildPeer == this;
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}
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/**
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* Add a listener that will be notified when a specific property changes.
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* @param propertyName the name of the property to listen on.
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* @param listener the listener to listen on the property.
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*/
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public void addPropertyChangeListener(String propertyName, PropertyChangeListener listener) {
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pcSupport.addPropertyChangeListener(propertyName, listener);
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}
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/**
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* Remove a listener to a certain property.
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*
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* @param propertyName the name of the property being listened on.
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* @param listener the listener listening on the property.
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*/
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public void removePropertyChangeListener(String propertyName, PropertyChangeListener listener) {
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pcSupport.removePropertyChangeListener(propertyName, listener);
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}
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/**
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* Add a listener that will be notified when a specific property
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* change is requested (a PropertyVetoException may be thrown) as
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* well as after the change is successfully made.
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*
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* @param propertyName the name of the property to listen on.
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* @param listener the listener to listen on the property.
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*/
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public void addVetoableChangeListener(String propertyName, VetoableChangeListener listener) {
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vcSupport.addVetoableChangeListener(propertyName, listener);
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}
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/**
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* Remove a listener to a certain property.
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*
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* @param propertyName the name of the property being listened on
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* @param listener the listener listening on the property.
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*/
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public void removeVetoableChangeListener(String propertyName, VetoableChangeListener listener) {
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vcSupport.removeVetoableChangeListener(propertyName, listener);
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}
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/**
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* Fire a property change.
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*
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* @param propertyName the name of the property that changed
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* @param oldVal the old value of the property
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* @param newVal the new value of the property
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*/
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public void firePropertyChange(String propertyName, Object oldVal, Object newVal) {
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pcSupport.firePropertyChange(propertyName, oldVal, newVal);
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}
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/**
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* Fire a vetoable property change.
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*
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* @param propertyName the name of the property that changed
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* @param oldVal the old value of the property
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* @param newVal the new value of the property
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* @exception PropertyVetoException if the change is vetoed.
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*/
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public void fireVetoableChange(String propertyName, Object oldVal, Object newVal)
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throws PropertyVetoException {
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vcSupport.fireVetoableChange(propertyName, oldVal, newVal);
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}
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/**
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* Called by <code>BeanContextServices.revokeService()</code> to indicate that a service has been revoked.
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* If you have a reference to such a service, it should be
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* discarded and may no longer function properly.
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* <code>getService()</code> will no longer work on the specified
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* service class after this event has been fired.
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* <P>
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*
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* <EM>This method is meant to be overriden.</EM>
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* <code>BeanContextChildSupport</code>'s implementation does
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* nothing.
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*
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* @param event the service revoked event.
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* @see java.beans.beancontext.BeanContextServices#revokeService(java.lang.Class,java.beans.beancontext.BeanContextServiceProvider,boolean)
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*/
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public void serviceRevoked(BeanContextServiceRevokedEvent event) {
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}
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/**
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* Called by <code>BeanContextServices</code> whenever a service is made available.
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* <P>
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*
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* <EM>This method is meant to be overriden.</EM>
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* <code>BeanContextChildSupport</code>'s implementation does
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* nothing.
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*
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* @param event the service revoked event, with useful information
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* about the new service.
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*/
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public void serviceAvailable(BeanContextServiceAvailableEvent event) {
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}
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/**
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* Called by <code>setBeanContext()</code> to determine whether the set should be rejected.
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* <P>
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*
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* <EM>This method is meant to be overriden.</EM>
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* <code>BeanContextChildSupport</code>'s implementation simply
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* returns <code>true</code>.
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*
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* @param newBeanContext the new parent.
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* @return whether to allow the parent to be changed to the new
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* value.
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*/
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public boolean validatePendingSetBeanContext(BeanContext newBeanContext) {
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return true;
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}
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/**
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* Called by <code>setBeanContext()</code> to release resources of a what will soon no longer be the parent.
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* <P>
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*
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* <EM>This method is meant to be overriden.</EM>
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* <code>BeanContextChildSupport</code>'s implementation does
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* nothing.
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*/
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protected void releaseBeanContextResources() {
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}
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/**
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* Called by <code>setBeanContext()</code> to grab resources when the parent has been set.
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* <P>
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*
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* <EM>This method is meant to be overriden.</EM>
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* <code>BeanContextChildSupport</code>'s implementation does
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* nothing.
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*/
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protected void initializeBeanContextResources() {
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}
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}
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