urlclassloader.java

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/*
 * @(#)URLClassLoader.java	1.81 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.net;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.io.File;
import java.io.FilePermission;
import java.io.InputStream;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandlerFactory;
import java.util.Enumeration;
import java.util.NoSuchElementException;
import java.util.StringTokenizer;
import java.util.jar.Manifest;
import java.util.jar.Attributes;
import java.util.jar.Attributes.Name;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;
import java.security.AccessController;
import java.security.AccessControlContext;
import java.security.SecureClassLoader;
import java.security.CodeSource;
import java.security.Permission;
import java.security.PermissionCollection;
import sun.misc.Resource;
import sun.misc.URLClassPath;
import sun.net.www.ParseUtil;
import sun.security.util.SecurityConstants;

/**
 * This class loader is used to load classes and resources from a search
 * path of URLs referring to both JAR files and directories. Any URL that
 * ends with a '/' is assumed to refer to a directory. Otherwise, the URL
 * is assumed to refer to a JAR file which will be opened as needed.
 * <p>
 * The AccessControlContext of the thread that created the instance of
 * URLClassLoader will be used when subsequently loading classes and
 * resources.
 * <p>
 * The classes that are loaded are by default granted permission only to
 * access the URLs specified when the URLClassLoader was created.
 *
 * @author  David Connelly
 * @version 1.72 10/17/00
 * @since   1.2
 */
public class URLClassLoader extends SecureClassLoader {
    /* The search path for classes and resources */
    private URLClassPath ucp;

    /* The context to be used when loading classes and resources */
    private AccessControlContext acc;

    /**
     * Constructs a new URLClassLoader for the given URLs. The URLs will be
     * searched in the order specified for classes and resources after first
     * searching in the specified parent class loader. Any URL that ends with
     * a '/' is assumed to refer to a directory. Otherwise, the URL is assumed
     * to refer to a JAR file which will be downloaded and opened as needed.
     *
     * <p>If there is a security manager, this method first
     * calls the security manager's <code>checkCreateClassLoader</code> method
     * to ensure creation of a class loader is allowed.
     * 
     * @param urls the URLs from which to load classes and resources
     * @param parent the parent class loader for delegation
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkCreateClassLoader</code> method doesn't allow 
     *             creation of a class loader.
     * @see SecurityManager#checkCreateClassLoader
     */
    public URLClassLoader(URL[] urls, ClassLoader parent) {
	super(parent);
	// this is to make the stack depth consistent with 1.1
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkCreateClassLoader();
	}
	ucp = new URLClassPath(urls);
	acc = AccessController.getContext();
    }

    /**
     * Constructs a new URLClassLoader for the specified URLs using the
     * default delegation parent <code>ClassLoader</code>. The URLs will
     * be searched in the order specified for classes and resources after
     * first searching in the parent class loader. Any URL that ends with
     * a '/' is assumed to refer to a directory. Otherwise, the URL is
     * assumed to refer to a JAR file which will be downloaded and opened
     * as needed.
     *
     * <p>If there is a security manager, this method first
     * calls the security manager's <code>checkCreateClassLoader</code> method
     * to ensure creation of a class loader is allowed.
     * 
     * @param urls the URLs from which to load classes and resources
     *
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkCreateClassLoader</code> method doesn't allow 
     *             creation of a class loader.
     * @see SecurityManager#checkCreateClassLoader
     */
    public URLClassLoader(URL[] urls) {
	super();
	// this is to make the stack depth consistent with 1.1
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkCreateClassLoader();
	}
	ucp = new URLClassPath(urls);
	acc = AccessController.getContext();
    }

    /**
     * Constructs a new URLClassLoader for the specified URLs, parent
     * class loader, and URLStreamHandlerFactory. The parent argument
     * will be used as the parent class loader for delegation. The
     * factory argument will be used as the stream handler factory to
     * obtain protocol handlers when creating new URLs.
     *
     * <p>If there is a security manager, this method first
     * calls the security manager's <code>checkCreateClassLoader</code> method
     * to ensure creation of a class loader is allowed.
     *
     * @param urls the URLs from which to load classes and resources
     * @param parent the parent class loader for delegation
     * @param factory the URLStreamHandlerFactory to use when creating URLs
     *
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkCreateClassLoader</code> method doesn't allow 
     *             creation of a class loader.
     * @see SecurityManager#checkCreateClassLoader
     */
    public URLClassLoader(URL[] urls, ClassLoader parent,
			  URLStreamHandlerFactory factory) {
	super(parent);
	// this is to make the stack depth consistent with 1.1
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkCreateClassLoader();
	}
	ucp = new URLClassPath(urls, factory);
	acc = AccessController.getContext();
    }

    /**
     * Appends the specified URL to the list of URLs to search for
     * classes and resources.
     *
     * @param url the URL to be added to the search path of URLs
     */
    protected void addURL(URL url) {
	ucp.addURL(url);
    }

    /**
     * Returns the search path of URLs for loading classes and resources.
     * This includes the original list of URLs specified to the constructor,
     * along with any URLs subsequently appended by the addURL() method.
     * @return the search path of URLs for loading classes and resources.
     */
    public URL[] getURLs() {
	return ucp.getURLs();
    }

    /**
     * Finds and loads the class with the specified name from the URL search
     * path. Any URLs referring to JAR files are loaded and opened as needed
     * until the class is found.
     *
     * @param name the name of the class
     * @return the resulting class
     * @exception ClassNotFoundException if the class could not be found
     */
    protected Class findClass(final String name)
	 throws ClassNotFoundException
    {
	Class retValue = null;
	try {
	    retValue = (Class)
		AccessController.doPrivileged(new PrivilegedExceptionAction() {
		    /*
		     * Formerly, this method would throw an exception if
		     * resource res == null. This would be wrapped in
		     * a PrivilegedActionException then unwrapped in 
		     * the body of findClass (as it still can be).
		     * Fewer exceptions need to be allocated if we return null.
		     */
		    public Object run() throws ClassNotFoundException {
			String path = name.replace('.', '/').concat(".class");
			Resource res = ucp.getResource(path, false);
			if (res != null) {
			    try {
				return defineClass(name, res);
			    } catch (IOException e) {
				throw new ClassNotFoundException(name, e);
			    }
			}
			return null;
		    }
		}, acc);
	} catch (java.security.PrivilegedActionException pae) {
	    throw (ClassNotFoundException) pae.getException();
	}
	if (retValue == null){
	    throw new ClassNotFoundException(name);
	}
	return retValue;
    }

    /*
     * Defines a Class using the class bytes obtained from the specified
     * Resource. The resulting Class must be resolved before it can be
     * used.
     */
    private Class defineClass(String name, Resource res) throws IOException {
	int i = name.lastIndexOf('.');
	URL url = res.getCodeSourceURL();
	if (i != -1) {
	    String pkgname = name.substring(0, i);
	    // Check if package already loaded.
	    Package pkg = getPackage(pkgname);
	    Manifest man = res.getManifest();
	    if (pkg != null) {
		// Package found, so check package sealing.
		if (pkg.isSealed()) {
		    // Verify that code source URL is the same.
		    if (!pkg.isSealed(url)) {
			throw new SecurityException(
			    "sealing violation: package " + pkgname + " is sealed");
		    }

		} else {
		    // Make sure we are not attempting to seal the package
		    // at this code source URL.
		    if ((man != null) && isSealed(pkgname, man)) {
			throw new SecurityException(
			    "sealing violation: can't seal package " + pkgname + 
			    ": already loaded");
		    }
		}
	    } else {
		if (man != null) {
		    definePackage(pkgname, man, url);
		} else {
                    definePackage(pkgname, null, null, null, null, null, null, null);
                }
	    }
	}
	// Now read the class bytes and define the class
	byte[] b = res.getBytes();
	java.security.cert.Certificate[] certs = res.getCertificates();
	CodeSource cs = new CodeSource(url, certs);
	return defineClass(name, b, 0, b.length, cs);
    }

    /**
     * Defines a new package by name in this ClassLoader. The attributes
     * contained in the specified Manifest will be used to obtain package
     * version and sealing information. For sealed packages, the additional
     * URL specifies the code source URL from which the package was loaded.
     *
     * @param name  the package name
     * @param man   the Manifest containing package version and sealing
     *              information
     * @param url   the code source url for the package, or null if none
     * @exception   IllegalArgumentException if the package name duplicates
     *              an existing package either in this class loader or one
     *              of its ancestors
     * @return the newly defined Package object
     */
    protected Package definePackage(String name, Manifest man, URL url)
	throws IllegalArgumentException
    {
	String path = name.replace('.', '/').concat("/");