src/java.desktop/share/classes/java/beans/beancontext/BeanContextSupport.java - master - niceSOFT/openjdk21

src/java.desktop/share/classes/java/beans/beancontext/BeanContextSupport.java
1 431 строка47 KB
Sergey Bylokhov
8238170: BeanContextSupport remove and propertyChange can deadlock
29 янв 2023, 23:04
29 янв 2023, 23:04d4e9f5e
/*
 * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.beans.beancontext;

import java.awt.Component;
import java.awt.Container;
import java.beans.Beans;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.beans.PropertyVetoException;
import java.beans.VetoableChangeListener;
import java.beans.Visibility;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serial;
import java.io.Serializable;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Locale;
import java.util.Map;

/**
 * This helper class provides a utility implementation of the
 * java.beans.beancontext.BeanContext interface.
 * <p>
 * Since this class directly implements the BeanContext interface, the class
 * can, and is intended to be used either by subclassing this implementation,
 * or via ad-hoc delegation of an instance of this class from another.
 * </p>
 *
 * @author Laurence P. G. Cable
 * @since 1.2
 */
public class      BeanContextSupport extends BeanContextChildSupport
       implements BeanContext,
                  Serializable,
                  PropertyChangeListener,
                  VetoableChangeListener {

    /**
     * Use serialVersionUID from JDK 1.3 for interoperability.
     */
    @Serial
    private static final long serialVersionUID = -4879613978649577204L;

    /**
     *
     * Construct a BeanContextSupport instance
     *
     *
     * @param peer      The peer {@code BeanContext} we are
     *                  supplying an implementation for,
     *                  or {@code null}
     *                  if this object is its own peer
     * @param lcle      The current Locale for this BeanContext. If
     *                  {@code lcle} is {@code null}, the default locale
     *                  is assigned to the {@code BeanContext} instance.
     * @param dTime     The initial state,
     *                  {@code true} if in design mode,
     *                  {@code false} if runtime.
     * @param visible   The initial visibility.
     * @see java.util.Locale#getDefault()
     * @see java.util.Locale#setDefault(java.util.Locale)
     */
    public BeanContextSupport(BeanContext peer, Locale lcle, boolean dTime, boolean visible) {
        super(peer);

        locale          = lcle != null ? lcle : Locale.getDefault();
        designTime      = dTime;
        okToUseGui      = visible;

        initialize();
    }

    /**
     * Create an instance using the specified Locale and design mode.
     *
     * @param peer      The peer {@code BeanContext} we
     *                  are supplying an implementation for,
     *                  or {@code null} if this object is its own peer
     * @param lcle      The current Locale for this {@code BeanContext}. If
     *                  {@code lcle} is {@code null}, the default locale
     *                  is assigned to the {@code BeanContext} instance.
     * @param dtime     The initial state, {@code true}
     *                  if in design mode,
     *                  {@code false} if runtime.
     * @see java.util.Locale#getDefault()
     * @see java.util.Locale#setDefault(java.util.Locale)
     */
    public BeanContextSupport(BeanContext peer, Locale lcle, boolean dtime) {
        this (peer, lcle, dtime, true);
    }

    /**
     * Create an instance using the specified locale
     *
     * @param peer      The peer BeanContext we are
     *                  supplying an implementation for,
     *                  or {@code null} if this object
     *                  is its own peer
     * @param lcle      The current Locale for this
     *                  {@code BeanContext}. If
     *                  {@code lcle} is {@code null},
     *                  the default locale
     *                  is assigned to the {@code BeanContext}
     *                  instance.
     * @see java.util.Locale#getDefault()
     * @see java.util.Locale#setDefault(java.util.Locale)
     */
    public BeanContextSupport(BeanContext peer, Locale lcle) {
        this (peer, lcle, false, true);
    }

    /**
     * Create an instance using with a default locale
     *
     * @param peer      The peer {@code BeanContext} we are
     *                  supplying an implementation for,
     *                  or {@code null} if this object
     *                  is its own peer
     */
    public BeanContextSupport(BeanContext peer) {
        this (peer, null, false, true);
    }

    /**
     * Create an instance that is not a delegate of another object
     */

    public BeanContextSupport() {
        this (null, null, false, true);
    }

    /**
     * Gets the instance of {@code BeanContext} that
     * this object is providing the implementation for.
     * @return the BeanContext instance
     */
    public BeanContext getBeanContextPeer() { return (BeanContext)getBeanContextChildPeer(); }

    /**
     * <p>
     * The instantiateChild method is a convenience hook
     * in BeanContext to simplify
     * the task of instantiating a Bean, nested,
     * into a {@code BeanContext}.
     * </p>
     * <p>
     * The semantics of the beanName parameter are defined by java.beans.Beans.instantiate.
     * </p>
     *
     * @param beanName the name of the Bean to instantiate within this BeanContext
     * @throws IOException if there is an I/O error when the bean is being deserialized
     * @throws ClassNotFoundException if the class
     * identified by the beanName parameter is not found
     * @return the new object
     */
    public Object instantiateChild(String beanName)
           throws IOException, ClassNotFoundException {
        BeanContext bc = getBeanContextPeer();

        return Beans.instantiate(bc.getClass().getClassLoader(), beanName, bc);
    }

    /**
     * Gets the number of children currently nested in
     * this BeanContext.
     *
     * @return number of children
     */
    public int size() {
        synchronized(children) {
            return children.size();
        }
    }

    /**
     * Reports whether or not this
     * {@code BeanContext} is empty.
     * A {@code BeanContext} is considered
     * empty when it contains zero
     * nested children.
     * @return if there are not children
     */
    public boolean isEmpty() {
        synchronized(children) {
            return children.isEmpty();
        }
    }

    /**
     * Determines whether or not the specified object
     * is currently a child of this {@code BeanContext}.
     * @param o the Object in question
     * @return if this object is a child
     */
    public boolean contains(Object o) {
        synchronized(children) {
            return children.containsKey(o);
        }
    }

    /**
     * Determines whether or not the specified object
     * is currently a child of this {@code BeanContext}.
     * @param o the Object in question
     * @return if this object is a child
     */
    public boolean containsKey(Object o) {
        synchronized(children) {
            return children.containsKey(o);
        }
    }

    /**
     * Gets all JavaBean or {@code BeanContext} instances
     * currently nested in this {@code BeanContext}.
     * @return an {@code Iterator} of the nested children
     */
    public Iterator<Object> iterator() {
        synchronized(children) {
            return new BCSIterator(children.keySet().iterator());
        }
    }

    /**
     * Gets all JavaBean or {@code BeanContext}
     * instances currently nested in this BeanContext.
     */
    public Object[] toArray() {
        synchronized(children) {
            return children.keySet().toArray();
        }
    }

    /**
     * Gets an array containing all children of
     * this {@code BeanContext} that match
     * the types contained in arry.
     * @param arry The array of object
     * types that are of interest.
     * @return an array of children
     */
    public Object[] toArray(Object[] arry) {
        synchronized(children) {
            return children.keySet().toArray(arry);
        }
    }


    /************************************************************************/

    /**
     * protected final subclass that encapsulates an iterator but implements
     * a noop remove() method.
     */

    protected static final class BCSIterator implements Iterator<Object> {
        BCSIterator(Iterator<?> i) { super(); src = i; }

        public boolean hasNext() { return src.hasNext(); }
        public Object       next()    { return src.next();    }
        public void    remove()  { /* do nothing */      }

        private Iterator<?> src;
    }

    /************************************************************************/

    /*
     * protected nested class containing per child information, an instance
     * of which is associated with each child in the "children" hashtable.
     * subclasses can extend this class to include their own per-child state.
     *
     * Note that this 'value' is serialized with the corresponding child 'key'
     * when the BeanContextSupport is serialized.
     */

    /**
     * A protected nested class containing per-child information
     * in the {@code children} hashtable.
     */
    protected class BCSChild implements Serializable {

        /**
         * Use serialVersionUID from JDK 1.7 for interoperability.
         */
        @Serial
        private static final long serialVersionUID = -5815286101609939109L;

        BCSChild(Object bcc, Object peer) {
            super();

            child     = bcc;
            proxyPeer = peer;
        }

        Object  getChild()                  { return child; }

        void    setRemovePending(boolean v) { removePending = v; }

        boolean isRemovePending()           { return removePending; }

        boolean isProxyPeer()               { return proxyPeer != null; }

        Object  getProxyPeer()              { return proxyPeer; }
        /*
         * fields
         */


        /**
         * The child.
         */
        @SuppressWarnings("serial") // Not statically typed as Serializable
        private Object child;

        /**
         * The peer if the child and the peer are related by an implementation
         * of BeanContextProxy
         */
        @SuppressWarnings("serial") // Not statically typed as Serializable
        private           Object   proxyPeer;

        private transient boolean  removePending;
    }

    /**
     * <p>
     * Subclasses can override this method to insert their own subclass
     * of Child without having to override add() or the other Collection
     * methods that add children to the set.
     * </p>
     * @param targetChild the child to create the Child on behalf of
     * @param peer        the peer if the tragetChild and the peer are related by an implementation of BeanContextProxy
     * @return Subtype-specific subclass of Child without overriding collection methods
     */

    protected BCSChild createBCSChild(Object targetChild, Object peer) {
        return new BCSChild(targetChild, peer);
    }

    /************************************************************************/

    /**
     * Adds/nests a child within this {@code BeanContext}.
     * <p>
     * Invoked as a side effect of java.beans.Beans.instantiate().
     * If the child object is not valid for adding then this method
     * throws an IllegalStateException.
     * </p>
     *
     *
     * @param targetChild The child objects to nest
     * within this {@code BeanContext}
     * @return true if the child was added successfully.
     * @see #validatePendingAdd
     */
    public boolean add(Object targetChild) {

        if (targetChild == null) throw new IllegalArgumentException();

        // The specification requires that we do nothing if the child
        // is already nested herein.

        if (children.containsKey(targetChild)) return false; // test before locking

        synchronized(BeanContext.globalHierarchyLock) {
            if (children.containsKey(targetChild)) return false; // check again

            if (!validatePendingAdd(targetChild)) {
                throw new IllegalStateException();
            }


            // The specification requires that we invoke setBeanContext() on the
            // newly added child if it implements the java.beans.beancontext.BeanContextChild interface

            BeanContextChild cbcc  = getChildBeanContextChild(targetChild);
            BeanContextChild  bccp = null;

            synchronized(targetChild) {

                if (targetChild instanceof BeanContextProxy) {
                    bccp = ((BeanContextProxy)targetChild).getBeanContextProxy();

                    if (bccp == null) throw new NullPointerException("BeanContextPeer.getBeanContextProxy()");
                }

                BCSChild bcsc  = createBCSChild(targetChild, bccp);
                BCSChild pbcsc = null;

                synchronized (children) {
                    children.put(targetChild, bcsc);

                    if (bccp != null) children.put(bccp, pbcsc = createBCSChild(bccp, targetChild));
                }

                if (cbcc != null) synchronized(cbcc) {
                    try {
                        cbcc.setBeanContext(getBeanContextPeer());
                    } catch (PropertyVetoException pve) {

                        synchronized (children) {
                            children.remove(targetChild);

                            if (bccp != null) children.remove(bccp);
                        }

                        throw new IllegalStateException();
                    }

                    cbcc.addPropertyChangeListener("beanContext", childPCL);
                    cbcc.addVetoableChangeListener("beanContext", childVCL);
                }

                Visibility v = getChildVisibility(targetChild);

                if (v != null) {
                    if (okToUseGui)
                        v.okToUseGui();
                    else
                        v.dontUseGui();
                }

                if (getChildSerializable(targetChild) != null) serializable++;

                childJustAddedHook(targetChild, bcsc);

                if (bccp != null) {
                    v = getChildVisibility(bccp);

                    if (v != null) {
                        if (okToUseGui)
                            v.okToUseGui();
                        else
                            v.dontUseGui();
                    }

                    if (getChildSerializable(bccp) != null) serializable++;

                    childJustAddedHook(bccp, pbcsc);
                }


            }

            // The specification requires that we fire a notification of the change

            fireChildrenAdded(new BeanContextMembershipEvent(getBeanContextPeer(), bccp == null ? new Object[] { targetChild } : new Object[] { targetChild, bccp } ));

        }

        return true;
    }

    /**
     * Removes a child from this BeanContext.  If the child object is not
     * for adding then this method throws an IllegalStateException.
     * @param targetChild The child objects to remove
     * @see #validatePendingRemove
     */
    public boolean remove(Object targetChild) {
        return remove(targetChild, true);
    }

    /**
     * internal remove used when removal caused by
     * unexpected {@code setBeanContext} or
     * by {@code remove()} invocation.
     * @param targetChild the JavaBean, BeanContext, or Object to be removed
     * @param callChildSetBC used to indicate that
     * the child should be notified that it is no
     * longer nested in this {@code BeanContext}.
     * @return whether or not was present before being removed
     */
    protected boolean remove(Object targetChild, boolean callChildSetBC) {

        if (targetChild == null) throw new IllegalArgumentException();

        synchronized(BeanContext.globalHierarchyLock) {
            if (!containsKey(targetChild)) return false;

            if (!validatePendingRemove(targetChild)) {
                throw new IllegalStateException();
            }

            BCSChild bcsc  = children.get(targetChild);
            BCSChild pbcsc = null;
            Object   peer  = null;

            // we are required to notify the child that it is no longer nested here if
            // it implements java.beans.beancontext.BeanContextChild

            synchronized(targetChild) {
                if (callChildSetBC) {
                    BeanContextChild cbcc = getChildBeanContextChild(targetChild);
                    if (cbcc != null) synchronized(cbcc) {
                        cbcc.removePropertyChangeListener("beanContext", childPCL);
                        cbcc.removeVetoableChangeListener("beanContext", childVCL);

                        try {
                            cbcc.setBeanContext(null);
                        } catch (PropertyVetoException pve1) {
                            cbcc.addPropertyChangeListener("beanContext", childPCL);
                            cbcc.addVetoableChangeListener("beanContext", childVCL);
                            throw new IllegalStateException();
                        }

                    }
                }

                synchronized (children) {
                    children.remove(targetChild);

                    if (bcsc.isProxyPeer()) {
                        pbcsc = children.get(peer = bcsc.getProxyPeer());
                        children.remove(peer);
                    }
                }

                if (getChildSerializable(targetChild) != null) serializable--;

                childJustRemovedHook(targetChild, bcsc);

                if (peer != null) {
                    if (getChildSerializable(peer) != null) serializable--;

                    childJustRemovedHook(peer, pbcsc);
                }
            }

            fireChildrenRemoved(new BeanContextMembershipEvent(getBeanContextPeer(), peer == null ? new Object[] { targetChild } : new Object[] { targetChild, peer } ));

        }

        return true;
    }

    /**
     * Tests to see if all objects in the
     * specified {@code Collection} are children of
     * this {@code BeanContext}.
     * @param c the specified {@code Collection}
     *
     * @return {@code true} if all objects
     * in the collection are children of
     * this {@code BeanContext}, false if not.
     */
    @SuppressWarnings("rawtypes")
    public boolean containsAll(Collection c) {
        synchronized(children) {
            for (Object o : c)
                if(!contains(o))
                    return false;

            return true;
        }
    }

    /**
     * add Collection to set of Children (Unsupported)
     * implementations must synchronized on the hierarchy lock and "children" protected field
     * @throws UnsupportedOperationException thrown unconditionally by this implementation
     * @return this implementation unconditionally throws {@code UnsupportedOperationException}
     */
    @SuppressWarnings("rawtypes")
    public boolean addAll(Collection c) {
        throw new UnsupportedOperationException();
    }

    /**
     * remove all specified children (Unsupported)
     * implementations must synchronized on the hierarchy lock and "children" protected field
     * @throws UnsupportedOperationException thrown unconditionally by this implementation
     * @return this implementation unconditionally throws {@code UnsupportedOperationException}

     */
    @SuppressWarnings("rawtypes")
    public boolean removeAll(Collection c) {
        throw new UnsupportedOperationException();
    }


    /**
     * retain only specified children (Unsupported)
     * implementations must synchronized on the hierarchy lock and "children" protected field
     * @throws UnsupportedOperationException thrown unconditionally by this implementation
     * @return this implementation unconditionally throws {@code UnsupportedOperationException}
     */
    @SuppressWarnings("rawtypes")
    public boolean retainAll(Collection c) {
        throw new UnsupportedOperationException();
    }

    /**
     * clear the children (Unsupported)
     * implementations must synchronized on the hierarchy lock and "children" protected field
     * @throws UnsupportedOperationException thrown unconditionally by this implementation
     */
    public void clear() {
        throw new UnsupportedOperationException();
    }

    /**
     * Adds a BeanContextMembershipListener
     *
     * @param  bcml the BeanContextMembershipListener to add
     * @throws NullPointerException if the argument is null
     */

    public void addBeanContextMembershipListener(BeanContextMembershipListener bcml) {
        if (bcml == null) throw new NullPointerException("listener");

        synchronized(bcmListeners) {
            if (bcmListeners.contains(bcml))
                return;
            else
                bcmListeners.add(bcml);
        }
    }

    /**
     * Removes a BeanContextMembershipListener
     *
     * @param  bcml the BeanContextMembershipListener to remove
     * @throws NullPointerException if the argument is null
     */

    public void removeBeanContextMembershipListener(BeanContextMembershipListener bcml) {
        if (bcml == null) throw new NullPointerException("listener");

        synchronized(bcmListeners) {
            if (!bcmListeners.contains(bcml))
                return;
            else
                bcmListeners.remove(bcml);
        }
    }

    /**
     * @param name the name of the resource requested.
     * @param bcc  the child object making the request.
     *
     * @return  the requested resource as an InputStream
     * @throws  NullPointerException if the argument is null
     */

    public InputStream getResourceAsStream(String name, BeanContextChild bcc) {
        if (name == null) throw new NullPointerException("name");
        if (bcc  == null) throw new NullPointerException("bcc");

        if (containsKey(bcc)) {
            ClassLoader cl = bcc.getClass().getClassLoader();

            return cl != null ? cl.getResourceAsStream(name)
                              : ClassLoader.getSystemResourceAsStream(name);
        } else throw new IllegalArgumentException("Not a valid child");
    }

    /**
     * @param name the name of the resource requested.
     * @param bcc  the child object making the request.
     *
     * @return the requested resource as an InputStream
     */

    public URL getResource(String name, BeanContextChild bcc) {
        if (name == null) throw new NullPointerException("name");
        if (bcc  == null) throw new NullPointerException("bcc");

        if (containsKey(bcc)) {
            ClassLoader cl = bcc.getClass().getClassLoader();

            return cl != null ? cl.getResource(name)
                              : ClassLoader.getSystemResource(name);
        } else throw new IllegalArgumentException("Not a valid child");
    }

    /**
     * Sets the new design time value for this {@code BeanContext}.
     * @param dTime the new designTime value
     */
    public synchronized void setDesignTime(boolean dTime) {
        if (designTime != dTime) {
            designTime = dTime;

            firePropertyChange("designMode", Boolean.valueOf(!dTime), Boolean.valueOf(dTime));
        }
    }


    /**
     * Reports whether or not this object is in
     * currently in design time mode.
     * @return {@code true} if in design time mode,
     * {@code false} if not
     */
    public synchronized boolean isDesignTime() { return designTime; }

    /**
     * Sets the locale of this BeanContext.
     * @param newLocale the new locale. This method call will have
     *        no effect if newLocale is {@code null}.
     * @throws PropertyVetoException if the new value is rejected
     */
    public synchronized void setLocale(Locale newLocale) throws PropertyVetoException {

        if ((locale != null && !locale.equals(newLocale)) && newLocale != null) {
            Locale old = locale;

            fireVetoableChange("locale", old, newLocale); // throws

            locale = newLocale;

            firePropertyChange("locale", old, newLocale);
        }
    }

    /**
     * Gets the locale for this {@code BeanContext}.
     *
     * @return the current Locale of the {@code BeanContext}
     */
    public synchronized Locale getLocale() { return locale; }

    /**
     * <p>
     * This method is typically called from the environment in order to determine
     * if the implementor "needs" a GUI.
     * </p>
     * <p>
     * The algorithm used herein tests the BeanContextPeer, and its current children
     * to determine if they are either Containers, Components, or if they implement
     * Visibility and return needsGui() == true.
     * </p>
     * @return {@code true} if the implementor needs a GUI
     */
    public synchronized boolean needsGui() {
        BeanContext bc = getBeanContextPeer();

        if (bc != this) {
            if (bc instanceof Visibility) return ((Visibility)bc).needsGui();

            if (bc instanceof Container || bc instanceof Component)
                return true;
        }

        synchronized(children) {
            for (Object c : children.keySet()) {
                try {
                    return ((Visibility)c).needsGui();
                } catch (ClassCastException cce) {
                    // do nothing ...
                }

                if (c instanceof Container || c instanceof Component)
                    return true;
            }
        }

        return false;
    }

    /**
     * notify this instance that it may no longer render a GUI.
     */

    public synchronized void dontUseGui() {
        if (okToUseGui) {
            okToUseGui = false;

            // lets also tell the Children that can that they may not use their GUI's
            synchronized(children) {
                for (Object c : children.keySet()) {
                    Visibility v = getChildVisibility(c);

                    if (v != null) v.dontUseGui();
                }
            }
        }
    }

    /**
     * Notify this instance that it may now render a GUI
     */

    public synchronized void okToUseGui() {
        if (!okToUseGui) {
            okToUseGui = true;

            // lets also tell the Children that can that they may use their GUI's
            synchronized(children) {
                for (Object c : children.keySet()) {
                    Visibility v = getChildVisibility(c);

                    if (v != null) v.okToUseGui();
                }
            }
        }
    }

    /**
     * Used to determine if the {@code BeanContext}
     * child is avoiding using its GUI.
     * @return is this instance avoiding using its GUI?
     * @see Visibility
     */
    public boolean avoidingGui() {
        return !okToUseGui && needsGui();
    }

    /**
     * Is this {@code BeanContext} in the
     * process of being serialized?
     * @return if this {@code BeanContext} is
     * currently being serialized
     */
    public boolean isSerializing() { return serializing; }

    /**
     * Returns an iterator of all children
     * of this {@code BeanContext}.
     * @return an iterator for all the current BCSChild values
     */
    protected Iterator<BCSChild> bcsChildren() { synchronized(children) { return children.values().iterator();  } }

    /**
     * called by writeObject after defaultWriteObject() but prior to
     * serialization of currently serializable children.
     *
     * This method may be overridden by subclasses to perform custom
     * serialization of their state prior to this superclass serializing
     * the children.
     *
     * This method should not however be used by subclasses to replace their
     * own implementation (if any) of writeObject().
     * @param oos the {@code ObjectOutputStream} to use during serialization
     * @throws IOException if serialization failed
     */

    protected void bcsPreSerializationHook(ObjectOutputStream oos) throws IOException {
    }

    /**
     * called by readObject after defaultReadObject() but prior to
     * deserialization of any children.
     *
     * This method may be overridden by subclasses to perform custom
     * deserialization of their state prior to this superclass deserializing
     * the children.
     *
     * This method should not however be used by subclasses to replace their
     * own implementation (if any) of readObject().
     * @param ois the {@code ObjectInputStream} to use during deserialization
     * @throws IOException if deserialization failed
     * @throws ClassNotFoundException if needed classes are not found
     */

    protected void bcsPreDeserializationHook(ObjectInputStream ois) throws IOException, ClassNotFoundException {
    }

    /**
     * Called by readObject with the newly deserialized child and BCSChild.
     * @param child the newly deserialized child
     * @param bcsc the newly deserialized BCSChild
     */
    protected void childDeserializedHook(Object child, BCSChild bcsc) {
        synchronized(children) {
            children.put(child, bcsc);
        }
    }

    /**
     * Used by writeObject to serialize a Collection.
     * @param oos the {@code ObjectOutputStream}
     * to use during serialization
     * @param coll the {@code Collection} to serialize
     * @throws IOException if serialization failed
     */
    protected final void serialize(ObjectOutputStream oos, Collection<?> coll) throws IOException {
        int      count   = 0;
        Object[] objects = coll.toArray();

        for (int i = 0; i < objects.length; i++) {
            if (objects[i] instanceof Serializable)
                count++;
            else
                objects[i] = null;
        }

        oos.writeInt(count); // number of subsequent objects

        for (int i = 0; count > 0; i++) {
            Object o = objects[i];

            if (o != null) {
                oos.writeObject(o);
                count--;
            }
        }
    }

    /**
     * used by readObject to deserialize a collection.
     * @param ois the ObjectInputStream to use
     * @param coll the Collection
     * @throws IOException if deserialization failed
     * @throws ClassNotFoundException if needed classes are not found
     */
    @SuppressWarnings({"rawtypes", "unchecked"})
    protected final void deserialize(ObjectInputStream ois, Collection coll) throws IOException, ClassNotFoundException {
        int count = 0;

        count = ois.readInt();

        while (count-- > 0) {
            coll.add(ois.readObject());
        }
    }

    /**
     * Used to serialize all children of
     * this {@code BeanContext}.
     * @param oos the {@code ObjectOutputStream}
     * to use during serialization
     * @throws IOException if serialization failed
     */
    public final void writeChildren(ObjectOutputStream oos) throws IOException {
        if (serializable <= 0) return;

        boolean prev = serializing;

        serializing = true;

        int count = 0;

        synchronized(children) {
            Iterator<Map.Entry<Object, BCSChild>> i = children.entrySet().iterator();

            while (i.hasNext() && count < serializable) {
                Map.Entry<Object, BCSChild> entry = i.next();

                if (entry.getKey() instanceof Serializable) {
                    try {
                        oos.writeObject(entry.getKey());   // child
                        oos.writeObject(entry.getValue()); // BCSChild
                    } catch (IOException ioe) {
                        serializing = prev;
                        throw ioe;
                    }
                    count++;
                }
            }
        }

        serializing = prev;

        if (count != serializable) {
            throw new IOException("wrote different number of children than expected");
        }

    }

    /**
     * Serialize the BeanContextSupport, if this instance has a distinct
     * peer (that is this object is acting as a delegate for another) then
     * the children of this instance are not serialized here due to a
     * 'chicken and egg' problem that occurs on deserialization of the
     * children at the same time as this instance.
     *
     * Therefore in situations where there is a distinct peer to this instance
     * it should always call writeObject() followed by writeChildren() and
     * readObject() followed by readChildren().
     *
     * @param  oos the {@code ObjectOutputStream} to write
     * @throws IOException if an I/O error occurs
     */
    @Serial
    private synchronized void writeObject(ObjectOutputStream oos) throws IOException {
        serializing = true;

        synchronized (BeanContext.globalHierarchyLock) {
            try {
                oos.defaultWriteObject(); // serialize the BeanContextSupport object

                bcsPreSerializationHook(oos);

                if (serializable > 0 && this.equals(getBeanContextPeer()))
                    writeChildren(oos);

                serialize(oos, (Collection)bcmListeners);
            } finally {
                serializing = false;
            }
        }
    }

    /**
     * When an instance of this class is used as a delegate for the
     * implementation of the BeanContext protocols (and its subprotocols)
     * there exists a 'chicken and egg' problem during deserialization
     * @param ois the ObjectInputStream to use
     * @throws IOException if deserialization failed
     * @throws ClassNotFoundException if needed classes are not found
     */

    public final void readChildren(ObjectInputStream ois) throws IOException, ClassNotFoundException {
        int count = serializable;

        while (count-- > 0) {
            Object child = ois.readObject();
            BCSChild bscc = (BCSChild) ois.readObject();

            synchronized(child) {
                BeanContextChild bcc = null;

                try {
                    bcc = (BeanContextChild)child;
                } catch (ClassCastException cce) {
                    // do nothing;
                }

                if (bcc != null) {
                    try {
                        bcc.setBeanContext(getBeanContextPeer());

                       bcc.addPropertyChangeListener("beanContext", childPCL);
                       bcc.addVetoableChangeListener("beanContext", childVCL);

                    } catch (PropertyVetoException pve) {
                        continue;
                    }
                }

                childDeserializedHook(child, bscc);
            }
        }
    }

    /**
     * deserialize contents ... if this instance has a distinct peer the
     * children are *not* serialized here, the peer's readObject() must call
     * readChildren() after deserializing this instance.
     *
     * @param  ois the {@code ObjectInputStream} to read
     * @throws ClassNotFoundException if the class of a serialized object could
     *         not be found
     * @throws IOException if an I/O error occurs
     */
    @Serial
    private synchronized void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {

        synchronized(BeanContext.globalHierarchyLock) {
            ois.defaultReadObject();

            initialize();

            bcsPreDeserializationHook(ois);

            if (serializable > 0 && this.equals(getBeanContextPeer()))
                readChildren(ois);

            deserialize(ois, bcmListeners = new ArrayList<>(1));
        }
    }

    /**
     * subclasses may envelope to monitor veto child property changes.
     */

    public void vetoableChange(PropertyChangeEvent pce) throws PropertyVetoException {
        String propertyName = pce.getPropertyName();
        Object source       = pce.getSource();

        synchronized(children) {
            if ("beanContext".equals(propertyName) &&
                containsKey(source)                    &&
                !getBeanContextPeer().equals(pce.getNewValue())
            ) {
                if (!validatePendingRemove(source)) {
                    throw new PropertyVetoException("current BeanContext vetoes setBeanContext()", pce);
                } else children.get(source).setRemovePending(true);
            }
        }
    }

    /**
     * subclasses may envelope to monitor child property changes.
     */

    public void propertyChange(PropertyChangeEvent pce) {
        String propertyName = pce.getPropertyName();
        Object source       = pce.getSource();

        if ("beanContext".equals(propertyName)) {
            synchronized (BeanContext.globalHierarchyLock) {
                synchronized (children) {
                    if (containsKey(source)
                            && children.get(source).isRemovePending())
                    {
                        BeanContext bc = getBeanContextPeer();

                        if (bc.equals(pce.getOldValue())
                                && !bc.equals(pce.getNewValue()))
                        {
                            remove(source, false);
                        } else {
                            children.get(source).setRemovePending(false);
                        }
                    }
                }
            }
        }
    }

    /**
     * <p>
     * Subclasses of this class may override, or envelope, this method to
     * add validation behavior for the BeanContext to examine child objects
     * immediately prior to their being added to the BeanContext.
     * </p>
     *
     * @param targetChild the child to create the Child on behalf of
     * @return true iff the child may be added to this BeanContext, otherwise false.
     */

    protected boolean validatePendingAdd(Object targetChild) {
        return true;
    }

    /**
     * <p>
     * Subclasses of this class may override, or envelope, this method to
     * add validation behavior for the BeanContext to examine child objects
     * immediately prior to their being removed from the BeanContext.
     * </p>
     *
     * @param targetChild the child to create the Child on behalf of
     * @return true iff the child may be removed from this BeanContext, otherwise false.
     */

    protected boolean validatePendingRemove(Object targetChild) {
        return true;
    }

    /**
     * subclasses may override this method to simply extend add() semantics
     * after the child has been added and before the event notification has
     * occurred. The method is called with the child synchronized.
     * @param child the child
     * @param bcsc the BCSChild
     */

    protected void childJustAddedHook(Object child, BCSChild bcsc) {
    }

    /**
     * subclasses may override this method to simply extend remove() semantics
     * after the child has been removed and before the event notification has
     * occurred. The method is called with the child synchronized.
     * @param child the child
     * @param bcsc the BCSChild
     */

    protected void childJustRemovedHook(Object child, BCSChild bcsc) {
    }

    /**
     * Gets the Component (if any) associated with the specified child.
     * @param child the specified child
     * @return the Component (if any) associated with the specified child.
     */
    protected static final Visibility getChildVisibility(Object child) {
        try {
            return (Visibility)child;
        } catch (ClassCastException cce) {
            return null;
        }
    }

    /**
     * Gets the Serializable (if any) associated with the specified Child
     * @param child the specified child
     * @return the Serializable (if any) associated with the specified Child
     */
    protected static final Serializable getChildSerializable(Object child) {
        try {
            return (Serializable)child;
        } catch (ClassCastException cce) {
            return null;
        }
    }

    /**
     * Gets the PropertyChangeListener
     * (if any) of the specified child
     * @param child the specified child
     * @return the PropertyChangeListener (if any) of the specified child
     */
    protected static final PropertyChangeListener getChildPropertyChangeListener(Object child) {
        try {
            return (PropertyChangeListener)child;
        } catch (ClassCastException cce) {
            return null;
        }
    }

    /**
     * Gets the VetoableChangeListener
     * (if any) of the specified child
     * @param child the specified child
     * @return the VetoableChangeListener (if any) of the specified child
     */
    protected static final VetoableChangeListener getChildVetoableChangeListener(Object child) {
        try {
            return (VetoableChangeListener)child;
        } catch (ClassCastException cce) {
            return null;
        }
    }

    /**
     * Gets the BeanContextMembershipListener
     * (if any) of the specified child
     * @param child the specified child
     * @return the BeanContextMembershipListener (if any) of the specified child
     */
    protected static final BeanContextMembershipListener getChildBeanContextMembershipListener(Object child) {
        try {
            return (BeanContextMembershipListener)child;
        } catch (ClassCastException cce) {
            return null;
        }
    }

    /**
     * Gets the BeanContextChild (if any) of the specified child
     * @param child the specified child
     * @return  the BeanContextChild (if any) of the specified child
     * @throws  IllegalArgumentException if child implements both BeanContextChild and BeanContextProxy
     */
    protected static final BeanContextChild getChildBeanContextChild(Object child) {
        try {
            BeanContextChild bcc = (BeanContextChild)child;

            if (child instanceof BeanContextChild && child instanceof BeanContextProxy)
                throw new IllegalArgumentException("child cannot implement both BeanContextChild and BeanContextProxy");
            else
                return bcc;
        } catch (ClassCastException cce) {
            try {
                return ((BeanContextProxy)child).getBeanContextProxy();
            } catch (ClassCastException cce1) {
                return null;
            }
        }
    }

    /**
     * Fire a BeanContextshipEvent on the BeanContextMembershipListener interface
     * @param bcme the event to fire
     */

    protected final void fireChildrenAdded(BeanContextMembershipEvent bcme) {
        Object[] copy;

        synchronized(bcmListeners) { copy = bcmListeners.toArray(); }

        for (int i = 0; i < copy.length; i++)
            ((BeanContextMembershipListener)copy[i]).childrenAdded(bcme);
    }

    /**
     * Fire a BeanContextshipEvent on the BeanContextMembershipListener interface
     * @param bcme the event to fire
     */

    protected final void fireChildrenRemoved(BeanContextMembershipEvent bcme) {
        Object[] copy;

        synchronized(bcmListeners) { copy = bcmListeners.toArray(); }

        for (int i = 0; i < copy.length; i++)
            ((BeanContextMembershipListener)copy[i]).childrenRemoved(bcme);
    }

    /**
     * protected method called from constructor and readObject to initialize
     * transient state of BeanContextSupport instance.
     *
     * This class uses this method to instantiate inner class listeners used
     * to monitor PropertyChange and VetoableChange events on children.
     *
     * subclasses may envelope this method to add their own initialization
     * behavior
     */

    protected synchronized void initialize() {
        children     = new HashMap<>(serializable + 1);
        bcmListeners = new ArrayList<>(1);

        childPCL = new PropertyChangeListener() {

            /*
             * this adaptor is used by the BeanContextSupport class to forward
             * property changes from a child to the BeanContext, avoiding
             * accidental serialization of the BeanContext by a badly
             * behaved Serializable child.
             */

            public void propertyChange(PropertyChangeEvent pce) {
                BeanContextSupport.this.propertyChange(pce);
            }
        };

        childVCL = new VetoableChangeListener() {

            /*
             * this adaptor is used by the BeanContextSupport class to forward
             * vetoable changes from a child to the BeanContext, avoiding
             * accidental serialization of the BeanContext by a badly
             * behaved Serializable child.
             */

            public void vetoableChange(PropertyChangeEvent pce) throws PropertyVetoException {
                BeanContextSupport.this.vetoableChange(pce);
             }
        };
    }

    /**
     * Gets a copy of the this BeanContext's children.
     * @return a copy of the current nested children
     */
    protected final Object[] copyChildren() {
        synchronized(children) { return children.keySet().toArray(); }
    }

    /**
     * Tests to see if two class objects,
     * or their names are equal.
     * @param first the first object
     * @param second the second object
     * @return true if equal, false if not
     */
    protected static final boolean classEquals(Class<?> first, Class<?> second) {
        return first.equals(second) || first.getName().equals(second.getName());
    }


    /*
     * fields
     */


    /**
     * all accesses to the {@code protected HashMap children} field
     * shall be synchronized on that object.
     */
    protected transient HashMap<Object, BCSChild>         children;

    /**
     * Currently serializable children.
     */
    private int serializable = 0; // children serializable

    /**
     * all accesses to the {@code protected ArrayList bcmListeners} field
     * shall be synchronized on that object.
     */
    protected transient ArrayList<BeanContextMembershipListener> bcmListeners;

    //

    /**
     * The current locale of this BeanContext.
     */
    protected           Locale          locale;

    /**
     * A {@code boolean} indicating if this
     * instance may now render a GUI.
     */
    protected           boolean         okToUseGui;


    /**
     * A {@code boolean} indicating whether or not
     * this object is currently in design time mode.
     */
    protected           boolean         designTime;

    /*
     * transient
     */

    private transient PropertyChangeListener childPCL;

    private transient VetoableChangeListener childVCL;

    private transient boolean                serializing;
}