/*
* Copyright (c) 2001-2007 Sun Microsystems, Inc. All rights reserved.
*
* The Sun Project JXTA(TM) Software License
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. The end-user documentation included with the redistribution, if any, must
* include the following acknowledgment: "This product includes software
* developed by Sun Microsystems, Inc. for JXTA(TM) technology."
* Alternately, this acknowledgment may appear in the software itself, if
* and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
* not be used to endorse or promote products derived from this software
* without prior written permission. For written permission, please contact
* Project JXTA at http://www.jxta.org.
*
* 5. Products derived from this software may not be called "JXTA", nor may
* "JXTA" appear in their name, without prior written permission of Sun.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SUN
* MICROSYSTEMS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* JXTA is a registered trademark of Sun Microsystems, Inc. in the United
* States and other countries.
*
* Please see the license information page at :
* <http://www.jxta.org/project/www/license.html> for instructions on use of
* the license in source files.
*
* ====================================================================
*
* This software consists of voluntary contributions made by many individuals
* on behalf of Project JXTA. For more information on Project JXTA, please see
* http://www.jxta.org.
*
* This license is based on the BSD license adopted by the Apache Foundation.
*/
package net.jxta.document;
import java.util.Enumeration;
/**
* An element represents a portion of a {@link StructuredDocument}. An element
* is identifiable by a <code>key</code> and may also optionally have a
* <code>value</code>. Each Element also maintains a collection of references
* to other elements, its <emphasis>children</emphasis>. Elements can be
* composed into arbitrary hierarchical structures forming complex data
* structures.
*
* <p/>Element instances are always associated with a
* {@link StructuredDocument}. A {@link StructuredDocument} is a specialized
* form of Element with additional features that make it appropriate for
* acting as the root of a hierarchy of elements.
*
* @see net.jxta.document.Document
* @see net.jxta.document.StructuredDocument
* @see net.jxta.document.StructuredDocumentFactory
* @see net.jxta.document.StructuredTextDocument
* @see net.jxta.document.TextElement
*/
public interface Element<E extends Element<E>> {
/**
* Get the key associated with this Element.
*
* @return The key of this Element.
*/
Object getKey();
/**
* Get the value (if any) associated with this Element.
*
* @return The value of this element, if any, otherwise null.
*/
Object getValue();
/**
* Get the root document element of the hierarchy this element belongs to.
*
* @return The root document element of this element's hierarchy.
*/
StructuredDocument getRoot();
/**
* Get the parent element of this element. If this Element has not been
* inserted into the Document then <code>null</code> is returned. If this
* element is the root element of the Document then it returns itself. ie.,
* <code>this == this.getParent()</code>.
*
* @return The parent of this element. If the element has no parent
* then null will be returned. If the element is the root Element of the
* hierarchy then it will return itself.
*/
E getParent();
/**
* Add a child element to this element. The child element must be from the
* document as the element it is to be added to. Elements are created using
* either {@link StructuredDocument#createElement(Object)} or
* {@link StructuredDocument#createElement(Object, Object)}.
*
* @param element The element to be added as a child.
*/
void appendChild(E element);
/**
* Returns an enumeration of the immediate children of this element.
*
* @return Enumeration containing all of the children of this element.
*/
Enumeration<E> getChildren();
/**
* Returns an enumeration of the immediate children of this element who
* match the specified key.
*
* @param key The key which will be matched against.
* @return Enumeration containing all of the matching children of this
* element.
*/
Enumeration<E> getChildren(Object key);
}