refjxtaloader.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 THE 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: RefJxtaLoader.java,v 1.12 2006/05/09 00:37:20 bondolo Exp $
 */

package net.jxta.impl.loader;

import java.io.StringReader;
import java.net.URL;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.WeakHashMap;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

import java.io.IOException;
import java.net.MalformedURLException;

import net.jxta.platform.JxtaLoader;
import net.jxta.document.MimeMediaType;
import net.jxta.document.StructuredDocument;
import net.jxta.document.StructuredDocumentFactory;
import net.jxta.platform.ModuleSpecID;
import net.jxta.protocol.ModuleImplAdvertisement;

import net.jxta.impl.peergroup.CompatibilityEquater;

/**
 * This class is the reference implementation of the JxtaLoader.
 */
public class RefJxtaLoader extends JxtaLoader {
    
    /**
     *  Log4J Logger
     */
    private final static transient  Logger LOG = Logger.getLogger(RefJxtaLoader.class.getName());

    private final CompatibilityEquater equator;
    
    /**
     * <p/><ul>
     *      <li>Keys are {@link net.jxta.platform.ModuleSpecID}.</li>
     *      <li>Values are {@link java.util.Map}.
     *          <ul>
     *              <li>Keys are {@link java.lang.String} Compatibility Statements serialized as XML UTF-8</li>
     *              <li>Values are {@link java.lang.Class}.</li>
     *          </ul>
     *      </li>
     *  </ul>
     */
    private final Map<ModuleSpecID,Map<String,Class>> classes = new HashMap<ModuleSpecID,Map<String,Class>>();
    
    /**
     *  Classes and ImplAdvs we have known. Weak Map so that classes can be GCed.
     */
    private final Map<Class,ModuleImplAdvertisement> implAdvs = new WeakHashMap<Class,ModuleImplAdvertisement>();
    
    /**
     * Construct a new loader for the specified URLS with the default parent
     * loader and specified compatibility equator.
     *
     *  @param urls  the URLs from which to load classes and resources.
     *  @param equator the equator to use in comparing compatibility statements.
     */
    public RefJxtaLoader( URL[] urls, CompatibilityEquater equator ) {
        this( urls, RefJxtaLoader.class.getClassLoader(), equator );
    }
    
    /**
     * Construct a new loader for the specified URLS with the specified parent
     * loader and specified compatibility equator.
     *
     *  @param urls  the URLs from which to load classes and resources.
     *  @param parent  the parent class loader for delegation.
     *  @param equator the equator to use in comparing compatibility statements.
     */
    public RefJxtaLoader( URL[] urls, ClassLoader parent, CompatibilityEquater equator ) {
        super( urls, parent );
        this.equator = equator;
    }
    
    /**
     * Make a stub for a version that uses URL, so that code that load
     * services can be written properly, even if it works only for classes
     * that do not need download.
     */
    protected Class loadClass(String name, URL url, boolean resolve)
    throws ClassNotFoundException {
        try {
            return loadClass(name, resolve);
        } catch (ClassNotFoundException e) {
            if (url != null ) {
                addURL( url );
                return loadClass( name, resolve );
            } else {
                throw e;
            }
        }
    }
    
    /**
     *  {@inheritDoc}
     */
    public Class loadClass(String name, boolean resolve ) throws ClassNotFoundException {
        
        Class newClass = findLoadedClass( name );
        
        if (newClass == null ) { // I'd rather say parent.loadClass() but it is private
            try {
                newClass = super.loadClass(name, false );
            } catch (ClassNotFoundException ignored) {
                // that's ok
                ;
            }
        }
        
        if (newClass == null) {
            try {
                newClass = findSystemClass(name);
                if (newClass != null) {
                    return newClass;
                }
            } catch (ClassNotFoundException ignored) {
                // that's ok
                ;
            }
            
            // We need to also check if the Context ClassLoader associated to the
            // the current thread can load the class.
            if (newClass == null) {
                try {
                    newClass = Thread.currentThread().getContextClassLoader().loadClass(name);
                    if (newClass != null) {
                        return newClass;
                    }
                } catch (ClassNotFoundException ignored) {
                // that's ok
                ;
                }
            }
            
            //            try {
            //                byte[] buf = bytesForClass(name);
            //                newClass = defineClass(name, buf, 0, buf.length);
            //            } catch (IOException e) {
            //                throw new ClassNotFoundException(e.toString());
            //            }
        }
        
        if (resolve) {
            resolveClass(newClass);
        }
        
        return newClass;
    }
    
    //    /**
    //     *  {@inheritDoc}
    //     **/
    //    protected byte[] bytesForClass(String name)
    //    throws IOException, ClassNotFoundException {
    //
    //        File file = new File( dir, name.replace('.', File.separatorChar) + ".java");
    //        FileInputStream in = new FileInputStream(file);
    //        int length = (int) file.length();
    //        if (length == 0)
    //            throw new ClassNotFoundException(name);
    //        byte[] buf = new byte[length];
    //        in.read(buf);
    //        return buf;
    //    }
    
    /**
     * {@inheritDoc}
     */
    public synchronized Class findClass( ModuleSpecID spec ) throws ClassNotFoundException {
        
        Map<String,Class> compats = classes.get( spec );
        
        if( null == compats ) {
            throw new ClassNotFoundException( "No matching class for : " + spec );
        }
        
        Iterator eachCompat = compats.entrySet().iterator();
        
        while( eachCompat.hasNext() ) {
            Map.Entry anEntry = (Map.Entry) eachCompat.next();
            String aCompat = (String) anEntry.getKey();
            
            StructuredDocument asDoc;
            try {
                asDoc = StructuredDocumentFactory.newStructuredDocument( MimeMediaType.XMLUTF8, new StringReader( aCompat ) );
            } catch( IOException ignored ) {
                continue;
            }
            
            if( equator.compatible( asDoc ) ) {
                return (Class) anEntry.getValue();
            }
        }
        
        throw new ClassNotFoundException( spec.toString() );
    }
    
    /**
     * {@inheritDoc}
     */
    public Class loadClass( ModuleSpecID spec ) throws ClassNotFoundException {
        
        Class found = findClass( spec );
        
        resolveClass( found );
        
        return found;
    }
    
    /**
     * {@inheritDoc}
     */
    public Class loadClass( String name, URL url ) throws ClassNotFoundException {
        return loadClass( name, url, true );
    }
    
    /**
     * {@inheritDoc}
     */
    public synchronized Class defineClass( ModuleImplAdvertisement impl ) throws ClassFormatError {
        String asString = impl.getCompat().toString();
        
        Map compats = (Map) classes.get( impl.getModuleSpecID() );
        
        if( null == compats ) {
            compats = new HashMap();
            classes.put( impl.getModuleSpecID(), compats );
        }
        
        Class loaded = (Class) compats.get( asString );
        
        if ( null == loaded ) {
            try {
                loaded = loadClass( impl.getCode(), new URL( impl.getUri() ), false );
            } catch( ClassNotFoundException failed ) {
                throw new ClassFormatError( "Class '" + impl.getCode() + "' could not be loaded from : " +  impl.getUri() );
            } catch( MalformedURLException failed ) {
                throw new ClassFormatError( "Cannot load class '" + impl.getCode() + "' from : " +  impl.getUri() );
            }
            
            compats.put( asString, loaded );
            
            implAdvs.put( loaded, impl );
        }
        
        return loaded;
    }
    
    /**
     * {@inheritDoc}
     */
    public ModuleImplAdvertisement findModuleImplAdvertisement( Class clazz ) {
        ModuleImplAdvertisement result = implAdvs.get( clazz );
        
        return result;
    }
}