element.java

jxta_src_2.41b jxta 2.41b 最新版源码 from www.jxta.org

/*
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights reserved.
 *
 * 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 the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    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.
 * ====================================================================
 *
 * 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.
 *
 * $Id: Element.java,v 1.16 2003/05/13 19:35:34 bondolo Exp $
 */
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>. Elmenents 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 {
    
    /**
     * Get the key associated with this Element.
     *
     * @return Object The key of this Element.
     **/
    Object getKey();
    
    /**
     * Get the value (if any) associated with this Element.
     *
     * @return Object The value of this element, if any, otherwise null.
     **/
    Object getValue();
    
    /**
     *  Get the root Element of the hierarchy this Element belongs to.
     *
     *  @return StructuredDocument The root 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 Element 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.
     **/
    Element 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.
     *
     *  @param element the element to be added as a child
     **/
    void appendChild( Element element );
    
    /**
     *  Returns an enumeration of the immediate children of this element.
     *
     *  @return Enumeration An enumeration containing all of the children of
     *  this element.
     **/
    Enumeration getChildren();
    
    /**
     *  Returns an enumeration of the immediate children of this element whose
     *  name match the specified key.
     *
     *  @param key The key which will be matched against.
     *  @return Enumeration enumeration containing all of the children of this
     *  element.
     **/
    Enumeration getChildren( Object key );
}