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Tinder is a Java based XMPP library, providing an implementation for XMPP stanzas and components. Tinders origins lie in code that's shared between Jive Software's Openfire and Whack implementations. The implementation that's provided in Tinder hasn't been written again from scratch. Instead, code has been moved from the original projects into Tinder, preserving al of the existing features and functionality. Most of the code that's now in Tinder is based on the org.xmpp package implementation that previously existed in Openfire and Whack. This is the code that defines classes such as Packet, JID, IQ, Component and their extensions. Additionally, some multi-purpose code (such as the DataForm and Result Set Management implementations have been moved to Tinder as well.

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/**
 * Copyright (C) 2004-2009 Jive Software. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.xmpp.packet;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import net.jcip.annotations.NotThreadSafe;

import org.dom4j.DocumentFactory;
import org.dom4j.Element;
import org.dom4j.QName;

/**
 * A packet extension represents a child element of a Packet for a given qualified name. The
 * PacketExtension acts as a wrapper on a child element the same way Packet does for a whole
 * element. The wrapper provides an easy way to handle the packet extension.
 *
 * Subclasses of this class can be registered using the static variable
 * registeredExtensions. The registration process associates the new subclass
 * with a given qualified name (ie. element name and namespace). This information will be used by
 * {@link Packet#getExtension(String, String)} for locating the corresponding PacketExtension
 * subclass to return for the requested qualified name. Each PacketExtension must have a public
 * constructor that takes an Element instance as an argument. 
 *
 * @author Gaston Dombiak
 */
@NotThreadSafe
public class PacketExtension {
    
    protected static final DocumentFactory docFactory = DocumentFactory.getInstance();
    /**
     * Subclasses of PacketExtension should register the element name and namespace that the
     * subclass is using.
     */
    protected static final Map> registeredExtensions = new ConcurrentHashMap>();

    protected Element element;

    /**
     * Returns the extension class to use for the specified element name and namespace. For
     * instance, the DataForm class should be used for the element "x" and
     * namespace "jabber:x:data".
     *
     * @param name the child element name.
     * @param namespace the child element namespace.
     * @return the extension class to use for the specified element name and namespace.
     */
    public static Class getExtensionClass(String name, String namespace) {
        return registeredExtensions.get(QName.get(name, namespace));
    }

    /**
     * Constructs a new Packet extension using the specified name and namespace.
     *
     * @param name the child element name.
     * @param namespace the child element namespace.
     */
    public PacketExtension(String name, String namespace) {
        this.element = docFactory.createDocument().addElement(name, namespace);
    }

    /**
     * Constructs a new PacketExtension.
     *
     * @param element the XML Element that contains the packet extension contents.
     */
    public PacketExtension(Element element) {
        this.element = element;
    }

    /**
     * Returns the DOM4J Element that backs the packet. The element is the definitive
     * representation of the packet and can be manipulated directly to change
     * packet contents.
     *
     * @return the DOM4J Element that represents the packet.
     */
    public Element getElement() {
        return element;
    }

    /**
     * Creates a deep copy of this packet extension.
     *
     * @return a deep copy of this packet extension.
     */
    public PacketExtension createCopy() {
        Element copy = element.createCopy();
        docFactory.createDocument().add(copy);
        return new PacketExtension(element);
    }
}