--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/eclipse/jetty/util/component/Container.java	Wed Sep 07 21:15:48 2016 -0600
@@ -0,0 +1,305 @@
+//
+//  ========================================================================
+//  Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
+//  ------------------------------------------------------------------------
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+//
+
+package org.eclipse.jetty.util.component;
+import java.lang.ref.WeakReference;
+import java.util.EventListener;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import org.eclipse.jetty.util.LazyList;
+import org.eclipse.jetty.util.log.Log;
+import org.eclipse.jetty.util.log.Logger;
+
+/* ------------------------------------------------------------ */
+/** Container.
+ * This class allows a containment events to be generated from update methods.
+ * 
+ * The style of usage is: <pre>
+ *   public void setFoo(Foo foo)
+ *   {
+ *       getContainer().update(this,this.foo,foo,"foo");
+ *       this.foo=foo;
+ *   }
+ *   
+ *   public void setBars(Bar[] bars)
+ *   {
+ *       getContainer().update(this,this.bars,bars,"bar");
+ *       this.bars=bars;
+ *   }
+ * </pre>
+ */
+public class Container
+{
+    private static final Logger LOG = Log.getLogger(Container.class);
+    private final CopyOnWriteArrayList<Container.Listener> _listeners=new CopyOnWriteArrayList<Container.Listener>();
+    
+    public void addEventListener(Container.Listener listener)
+    {
+        _listeners.add(listener);
+    }
+    
+    public void removeEventListener(Container.Listener listener)
+    {
+        _listeners.remove(listener);
+    }
+    
+    /* ------------------------------------------------------------ */
+    /** Update single parent to child relationship.
+     * @param parent The parent of the child.
+     * @param oldChild The previous value of the child.  If this is non null and differs from <code>child</code>, then a remove event is generated.
+     * @param child The current child. If this is non null and differs from <code>oldChild</code>, then an add event is generated.
+     * @param relationship The name of the relationship
+     */
+    public void update(Object parent, Object oldChild, final Object child, String relationship)
+    {
+        if (oldChild!=null && !oldChild.equals(child))
+            remove(parent,oldChild,relationship);
+        if (child!=null && !child.equals(oldChild))
+            add(parent,child,relationship);
+    }
+    
+    /* ------------------------------------------------------------ */
+    /** Update single parent to child relationship.
+     * @param parent The parent of the child.
+     * @param oldChild The previous value of the child.  If this is non null and differs from <code>child</code>, then a remove event is generated.
+     * @param child The current child. If this is non null and differs from <code>oldChild</code>, then an add event is generated.
+     * @param relationship The name of the relationship
+     * @param addRemove If true add/remove is called for the new/old children as well as the relationships
+     */
+    public void update(Object parent, Object oldChild, final Object child, String relationship,boolean addRemove)
+    {
+        if (oldChild!=null && !oldChild.equals(child))
+        {
+            remove(parent,oldChild,relationship);
+            if (addRemove)
+                removeBean(oldChild);
+        }
+        
+        if (child!=null && !child.equals(oldChild))
+        {
+            if (addRemove)
+                addBean(child);
+            add(parent,child,relationship);
+        }
+    }
+
+    /* ------------------------------------------------------------ */
+    /** Update multiple parent to child relationship.
+     * @param parent The parent of the child.
+     * @param oldChildren The previous array of children.  A remove event is generated for any child in this array but not in the  <code>children</code> array.
+     * This array is modified and children that remain in the new children array are nulled out of the old children array.
+     * @param children The current array of children. An add event is generated for any child in this array but not in the <code>oldChildren</code> array.
+     * @param relationship The name of the relationship
+     */
+    public void update(Object parent, Object[] oldChildren, final Object[] children, String relationship)
+    {
+        update(parent,oldChildren,children,relationship,false);
+    }
+    
+    /* ------------------------------------------------------------ */
+    /** Update multiple parent to child relationship.
+     * @param parent The parent of the child.
+     * @param oldChildren The previous array of children.  A remove event is generated for any child in this array but not in the  <code>children</code> array.
+     * This array is modified and children that remain in the new children array are nulled out of the old children array.
+     * @param children The current array of children. An add event is generated for any child in this array but not in the <code>oldChildren</code> array.
+     * @param relationship The name of the relationship
+     * @param addRemove If true add/remove is called for the new/old children as well as the relationships
+     */
+    public void update(Object parent, Object[] oldChildren, final Object[] children, String relationship, boolean addRemove)
+    {
+        Object[] newChildren = null;
+        if (children!=null)
+        {
+            newChildren = new Object[children.length];
+        
+            for (int i=children.length;i-->0;)
+            {
+                boolean new_child=true;
+                if (oldChildren!=null)
+                {
+                    for (int j=oldChildren.length;j-->0;)
+                    {
+                        if (children[i]!=null && children[i].equals(oldChildren[j]))
+                        {
+                            oldChildren[j]=null;
+                            new_child=false;
+                        }
+                    }
+                }
+                if (new_child)
+                    newChildren[i]=children[i];
+            }
+        }
+        
+        if (oldChildren!=null)
+        {
+            for (int i=oldChildren.length;i-->0;)
+            {
+                if (oldChildren[i]!=null)
+                {
+                    remove(parent,oldChildren[i],relationship);
+                    if (addRemove)
+                        removeBean(oldChildren[i]);
+                }
+            }
+        }
+        
+        if (newChildren!=null)
+        {
+            for (int i=0;i<newChildren.length;i++)
+                if (newChildren[i]!=null)
+                {
+                    if (addRemove)
+                        addBean(newChildren[i]);
+                    add(parent,newChildren[i],relationship);
+                }
+        }
+    }
+
+    /* ------------------------------------------------------------ */
+    public void addBean(Object obj)
+    {
+        if (_listeners!=null)
+        {
+            for (int i=0; i<LazyList.size(_listeners); i++)
+            {
+                Listener listener=(Listener)LazyList.get(_listeners, i);
+                listener.addBean(obj);
+            }
+        }
+    }
+
+    /* ------------------------------------------------------------ */
+    public void removeBean(Object obj)
+    {
+        if (_listeners!=null)
+        {
+            for (int i=0; i<LazyList.size(_listeners); i++)
+                ((Listener)LazyList.get(_listeners, i)).removeBean(obj);
+        }
+    }
+    
+    /* ------------------------------------------------------------ */
+    /** Add a parent child relationship
+     * @param parent
+     * @param child
+     * @param relationship
+     */
+    private void add(Object parent, Object child, String relationship)
+    {
+        if (LOG.isDebugEnabled())
+            LOG.debug("Container "+parent+" + "+child+" as "+relationship);
+        if (_listeners!=null)
+        {
+            Relationship event=new Relationship(this,parent,child,relationship);
+            for (int i=0; i<LazyList.size(_listeners); i++)
+                ((Listener)LazyList.get(_listeners, i)).add(event);
+        }
+    }
+    
+    /* ------------------------------------------------------------ */
+    /** remove a parent child relationship
+     * @param parent
+     * @param child
+     * @param relationship
+     */
+    private void remove(Object parent, Object child, String relationship)
+    {
+        if (LOG.isDebugEnabled())
+            LOG.debug("Container "+parent+" - "+child+" as "+relationship);
+        if (_listeners!=null)
+        {
+            Relationship event=new Relationship(this,parent,child,relationship);
+            for (int i=0; i<LazyList.size(_listeners); i++)
+                ((Listener)LazyList.get(_listeners, i)).remove(event);
+        }
+    }
+    
+    /* ------------------------------------------------------------ */
+    /** A Container event.
+     * @see Listener
+     */
+    public static class Relationship
+    {
+        private final WeakReference<Object> _parent;
+        private final WeakReference<Object> _child;
+        private String _relationship;
+        private Container _container;
+        
+        private Relationship(Container container, Object parent,Object child, String relationship)
+        {
+            _container=container;
+            _parent=new WeakReference<Object>(parent);
+            _child=new WeakReference<Object>(child);
+            _relationship=relationship;
+        }
+        
+        public Container getContainer()
+        {
+            return _container;
+        }
+        
+        public Object getChild()
+        {
+            return _child.get();
+        }
+        
+        public Object getParent()
+        {
+            return _parent.get();
+        }
+        
+        public String getRelationship()
+        {
+            return _relationship;
+        }
+        
+        @Override
+        public String toString()
+        {
+            return _parent+"---"+_relationship+"-->"+_child;
+        }
+        
+        @Override
+        public int hashCode()
+        {
+            return _parent.hashCode()+_child.hashCode()+_relationship.hashCode();
+        }
+        
+        @Override
+        public boolean equals(Object o)
+        {
+            if (o==null || !(o instanceof Relationship))
+                return false;
+            Relationship r = (Relationship)o;
+            return r._parent.get()==_parent.get() && r._child.get()==_child.get() && r._relationship.equals(_relationship);
+        }
+    }
+    
+    /* ------------------------------------------------------------ */
+    /** Listener.
+     * A listener for Container events.
+     */
+    public interface Listener extends EventListener
+    {
+        public void addBean(Object bean);
+        public void removeBean(Object bean);
+        public void add(Container.Relationship relationship);
+        public void remove(Container.Relationship relationship);
+    }
+}