description.java

jxta-cms-src-2.4.zip 是官网上的比较稳定的CMS源代码。目前是最稳定的高版本。

/*
 * 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 THE APACHE SOFTWARE FOUNDATION 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: Description.java,v 1.3 2002/03/18 21:00:49 rmjohnson Exp $
 *
 */

package net.jxta.share.metadata;

import net.jxta.document.Element;

/** An implementation of the description metadata scheme.  The only metadata
 * stored is a plain english description of the content.  The format of a
 * description metadata element is as follows:<br><br>
 *
 *<code>&lt;metadata><br>
 *&nbsp;&nbsp;&lt;scheme><br>
 *&nbsp;&nbsp;&nbsp;&nbsp;&lt;name>description&lt;/name><br>
 *&nbsp;&nbsp;&nbsp;&nbsp;&lt;location><i>location of resource used to parse 
 * and query the scheme</i>&lt;/location><br>
 *&nbsp;&nbsp;&nbsp;&nbsp;&lt;content-type>text/plain&lt;/content-type><br>
 *&nbsp;&nbsp;&lt;/scheme><br>
 *&nbsp;&nbsp;<i>plain english description</i><br>
 *&lt;/metadata></code>
 *<br><br>
 *For an example of this class in use, see <a href="../../../../../ref/src/net/jxta/test/ShareDemo.java">net.jxta.test.ShareDemo</a> and <a href="../../../../../ref/src/net/jxta/test/SearchDemo.java">net.jxta.test.SearchDemo</a>.
 *
 *@see ContentMetadataFactory
 *@see Keywords
 *@version $Revision: 1.3 $
 *@author $Author: rmjohnson $
 */
public class Description extends ContentMetadata {
    
    /**The name of the metadata scheme implemented by this class.*/
    public static final String SN_DESCRIPTION = "description";

    /**The content type used by the description metadata scheme.*/
    public static final String DESCRIPTION_CONTENT_TYPE = "text/plain";    

    private String description;

    /**Create a MetadataQuery instance that can be used to query objects of
     * this class.
     *@param query the string to search for
     *@exception IllegalArgumentException if query is null
     */
    public static MetadataQuery newQuery(String query)
	throws IllegalArgumentException {
	if(query == null)
	    throw new IllegalArgumentException();
	return new DescriptionQuery(query);
    }

    /**A simple MetadataQuery implementation that can be used to search a
     * Description metadata object for a string.
     */
    public static class DescriptionQuery implements MetadataQuery {
	private String queryString;
	
	/**@param queryString the string to search for.  It is assumed that
	 * this is not null, if it is, <code>queryMetadata()</code> will throw
	 * a NullPointerException.
	 */
	public DescriptionQuery(String queryString) {
	    this.queryString = queryString;
	}

	/**Test if a ContentMetadata object matches this query.
	 *@param metadata the Description object to query.
	 *@return <code>Integer.MAX_VALUE</code> if the query string was found 
	 * in <code>metadata</code>'s value, <code>Integer.MIN_VALUE</code> if
	 * not.
	 *@exception IllegalArgumentException if <code>metadata</code> is not
	 * an instance of the Description class.
	 */
	public int queryMetadata(ContentMetadata metadata)
	    throws IllegalArgumentException {
	    String desc;
	    try {
		desc = ((Description)metadata).getDescription();
	    }catch(ClassCastException cce) {
		throw new IllegalArgumentException("metadata is not of the Description class");
	    }
	    if(desc.indexOf(queryString) != -1)
		return Integer.MAX_VALUE;
	    return Integer.MIN_VALUE;
	}
    }

    /**Return the ContentMetadataConstructor used to create instances of this
     * class.
     */
    public static ContentMetadataConstructor getConstructor() {
	return new ContentMetadataConstructor() {
		public ContentMetadata newInstance(Element metadataEl)
		throws IllegalArgumentException {
		    return new Description(metadataEl);
		}
	    };
    }

    /**Create a new Description object with a given string as the metadata.
     *@exception NullPointerException if <code>description</code> is null.
     */
    public Description(String description) {
	name = SN_DESCRIPTION;
	content_type = DESCRIPTION_CONTENT_TYPE;
	if(description == null)
	    throw new NullPointerException("description is null");
	this.description = description;
    }

    /**Create a Description instance from a <code>&lt;metadata></code> element.
     *@exception IllegalArgumentException if <code>el<code> was formatted
     * improperly.
     *@exception NullPointerException if <code>el</code> is null.
     */
    public Description(Element el) throws IllegalArgumentException {
	init(el);
	name = SN_DESCRIPTION;
	content_type = DESCRIPTION_CONTENT_TYPE;
	description = (String)el.getValue();
	if(description == null)
	    throw new IllegalArgumentException("metadata element's value is null");
    }

	/**A function for generating safe copies of this ContentMetadata object.
	 *
	 * @return a safe copy of this ContentMetadata object
	 */
    public Object clone() throws CloneNotSupportedException {
    	Description result = new Description(description);
    	result.location = location;
    	return result;
    }
    
    public String getValue() {
	return description;
    }

    /**Return the text of the description*/
    public String getDescription() {
	return description;
    }
}