rmiclassloader.java

《移动Agent技术》一书的所有章节源代码。

/*
 * @(#)RMIClassLoader.java	1.10 97/01/06
 * 
 * Copyright (c) 1995, 1996 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 * 
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 * 
 * CopyrightVersion 1.1_beta
 */

package java.rmi.server;

import java.net.MalformedURLException;
import java.net.URL;

/**
 * The RMIClassLoader class provides static methods for loading classes
 * over the network.  Classes can be loaded from either a particular URL,
 * or from the URL specified in the <b>java.rmi.server.codebase</b>
 * system property.
 * 
 * @version	1.10, 01/06/97
 * @author Ann Wollrath
 */
public class RMIClassLoader {
    /*
     * Disallow anyone from creating one of these.
     */
    private RMIClassLoader() {}

    private static LoaderHandler handler = null;

    private static synchronized LoaderHandler getHandler() 
    {
	if (handler == null) {
	    try {
		Class cl = Class.forName(LoaderHandler.packagePrefix +
					 ".LoaderHandler");
		handler = (LoaderHandler)cl.newInstance();
	    } catch (Exception e) {
		throw new Error("No LoaderHandler present");
	    }
	}
	return handler;
    }

    /**
     * Load a class from the URL specified in the
     * <b>java.rmi.server.codebase</b> property.
     * @param name  the name of the class to load
     * @return the Class object representing the loaded class
     * @exception MalformedURLException
     *            The system property <b>java.rmi.server.codebase</b>
     *            does not contain a valid URL.
     * @exception ClassNotFoundException
     *            A definition for the class could not
     *            be found at the codebase URL.
     */
    public static Class loadClass(String name)
	throws MalformedURLException, ClassNotFoundException
    {
	return getHandler().loadClass(name);
    }
    
    /**
     * Load a class from a URL.
     * @param codebase  the URL from which to load the class
     * @param name      the name of the class to load
     * @return the Class object representing the loaded class
     * @exception MalformedURLException
     *            The codebase paramater was null.
     * @exception ClassNotFoundException
     *            A definition for the class could not
     *            be found at the specified URL.
     */
    public static Class loadClass(URL codebase, String name)
	throws MalformedURLException, ClassNotFoundException
    {
	return getHandler().loadClass(codebase, name);
    }

    /**
     * Returns the security context of the given class loader
     * @param loader a class loader from which to get the security
     * 	      context
     * @return the security context (e.g., a URL)
     */
    public static Object getSecurityContext(ClassLoader loader)
    {
	return getHandler().getSecurityContext(loader);
    }
}