advertisementfactory.java

JXTA&#8482 is a set of open, generalized peer-to-peer (P2P) protocols that allow any networked devi

/*
 * Copyright (c) 2001-2007 Sun Microsystems, Inc.  All rights reserved.
 *  
 *  The Sun Project JXTA(TM) Software License
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 *  Redistribution and use in source and binary forms, with or without 
 *  modification, are permitted provided that the following conditions are met:
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 *  1. Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
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 *     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.
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 *  4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must 
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 *     Project JXTA at http://www.jxta.org.
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 *  Please see the license information page at :
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 *  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.
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package net.jxta.document;


import java.io.InputStream;
import java.io.Reader;
import java.util.HashMap;
import java.util.Map;

import java.io.IOException;
import java.util.NoSuchElementException;
import java.util.MissingResourceException;

import java.util.logging.Logger;
import java.util.logging.Level;
import net.jxta.logging.Logging;

import net.jxta.util.ClassFactory;


/**
 * A Factory class for constructing Advertisements. This class abstracts the
 * the implementations used to represent and create advertisements.
 *
 * <p/>Advertisements are core objects that are used to advertise a Peer, a
 * PeerGroup, a Service, a Pipe, etc. The Advertisement class provides a 
 * platform independent representation of core objects that can be exchanged
 * between different implementations (Java, C).
 *
 * <p/>The AdvertisementFactory extends the ClassFactory to register the various
 * types of advertisements into an internal table. The factory is called with
 * the Advertisement type requested to create the corresponding advertisement
 * type.
 *
 * <p/>The set of Advertisements types supported is loaded from the JXTA
 * classpath via the service provider interface.
 *
 * @see net.jxta.document.Advertisement
 * @see net.jxta.document.Document
 * @see net.jxta.document.MimeMediaType
 * @see net.jxta.peergroup.PeerGroup
 * @see net.jxta.protocol.PeerAdvertisement
 * @see net.jxta.protocol.PeerGroupAdvertisement
 * @see net.jxta.protocol.PipeAdvertisement
 */
public class AdvertisementFactory extends ClassFactory<String, AdvertisementFactory.Instantiator> {

    /**
     *  Logger
     */
    private static final Logger LOG = Logger.getLogger(AdvertisementFactory.class.getName());
    
    /**
     *  Interface for instantiators of Advertisements
     */
    public interface Instantiator {
        
        /**
         * Returns the identifying type of this Advertisement.
         *
         * @return String the type of advertisement
         */
        String getAdvertisementType();
        
        /**
         * Constructs an instance of {@link Advertisement} matching the type
         * specified by the <CODE>advertisementType</CODE> parameter.
         *
         *
         * @return The instance of {@link Advertisement}.
         */
        Advertisement newInstance();
        
        /**
         * Constructs an instance of {@link Advertisement} matching the type
         * specified by the <CODE>advertisementType</CODE> parameter.
         *
         * @param root Specifies a portion of a @link StructuredDocument} which
         * will be converted into an Advertisement.
         * @return The instance of {@link Advertisement}.
         */
        Advertisement newInstance(net.jxta.document.Element root);
    }
    
    /**
     *  This class is a singleton. This is the instance that backs the
     *  static methods.
     */
    private final static AdvertisementFactory factory = new AdvertisementFactory();
    
    /**
     *  This is the map of mime-types and constructors used by
     *  {@code newAdvertisement}.
     */
    private final Map<String, Instantiator> encodings = new HashMap<String, Instantiator>();
    
    /**
     *  If true then the pre-defined set of StructuredDocument sub-classes has
     *  been registered from the property containing them.
     */
    private boolean loadedProperty = false;
    
    /**
     *  Private constructor. This class is not meant to be instantiated except
     *  by itself.
     *
     */
    private AdvertisementFactory() {}
    
    /**
     *  Registers the pre-defined set of Advertisement sub-classes so that
     *  this factory can construct them.
     *
     *  @return true if at least one of the Advertisement sub-classes could
     *  be registered otherwise false.
     */
    private synchronized boolean loadProviders() {
        if (!factory.loadedProperty) {
            factory.loadedProperty = registerProviders(Advertisement.class.getName());
        }
        
        return factory.loadedProperty;
    }
    
    /**
     *  {@inheritDoc}
     */
    @Override
    protected Map<String, Instantiator> getAssocTable() {
        return encodings;
    }
    
    /**
     *  {@inheritDoc}
     */
    @Override
    public Class<Instantiator> getClassOfInstantiators() {
        // our key is the doctype names.
        return Instantiator.class;
    }
    
    /**
     *  {@inheritDoc}
     */
    @Override
    public Class<String> getClassForKey() {