/*
 * Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 in the LICENSE file that
 * accompanied this code).
 *
 * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.rmi.server;

import java.io.File;
import java.io.FilePermission;
import java.io.IOException;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;
import java.net.JarURLConnection;
import java.net.MalformedURLException;
import java.net.SocketPermission;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLConnection;
import java.security.AccessControlContext;
import java.security.CodeSource;
import java.security.Permission;
import java.security.Permissions;
import java.security.PermissionCollection;
import java.security.Policy;
import java.security.ProtectionDomain;
import java.rmi.server.LogStream;
import java.util.Arrays;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.IdentityHashMap;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.WeakHashMap;
import sun.reflect.misc.ReflectUtil;
import sun.rmi.runtime.Log;
import sun.security.action.GetPropertyAction;

LoaderHandler provides the implementation of the static
methods of the java.rmi.server.RMIClassLoader class.
Author:
     Ann Wollrath,      Peter Jones,      Laird Dornin/**
 * <code>LoaderHandler</code> provides the implementation of the static
 * methods of the <code>java.rmi.server.RMIClassLoader</code> class.
 *
 * @author      Ann Wollrath
 * @author      Peter Jones
 * @author      Laird Dornin
 */
public final class LoaderHandler {

    
RMI class loader log level /** RMI class loader log level */
    static final int logLevel = LogStream.parseLevel(
        java.security.AccessController.doPrivileged(
            new GetPropertyAction("sun.rmi.loader.logLevel")));

    /* loader system log */
    static final Log loaderLog =
        Log.getLog("sun.rmi.loader", "loader", LoaderHandler.logLevel);

    
value of "java.rmi.server.codebase" property, as cached at class
initialization time.  It may contain malformed URLs.
/**
     * value of "java.rmi.server.codebase" property, as cached at class
     * initialization time.  It may contain malformed URLs.
     */
    private static String codebaseProperty = null;
    static {
        String prop = java.security.AccessController.doPrivileged(
            new GetPropertyAction("java.rmi.server.codebase"));
        if (prop != null && prop.trim().length() > 0) {
            codebaseProperty = prop;
        }
    }

    
list of URLs represented by the codebase property, if valid /** list of URLs represented by the codebase property, if valid */
    private static URL[] codebaseURLs = null;

    
table of class loaders that use codebase property for annotation /** table of class loaders that use codebase property for annotation */
    private static final Map<ClassLoader, Void> codebaseLoaders =
        Collections.synchronizedMap(new IdentityHashMap<ClassLoader, Void>(5));
    static {
        for (ClassLoader codebaseLoader = ClassLoader.getSystemClassLoader();
             codebaseLoader != null;
             codebaseLoader = codebaseLoader.getParent())
        {
            codebaseLoaders.put(codebaseLoader, null);
        }
    }

    
table mapping codebase URL path and context class loader pairs
to class loader instances.  Entries hold class loaders with weak
references, so this table does not prevent loaders from being
garbage collected.
/**
     * table mapping codebase URL path and context class loader pairs
     * to class loader instances.  Entries hold class loaders with weak
     * references, so this table does not prevent loaders from being
     * garbage collected.
     */
    private static final HashMap<LoaderKey, LoaderEntry> loaderTable
        = new HashMap<LoaderKey, LoaderEntry>(5);

    
reference queue for cleared class loader entries /** reference queue for cleared class loader entries */
    private static final ReferenceQueue<Loader> refQueue
        = new ReferenceQueue<Loader>();

    /*
     * Disallow anyone from creating one of these.
     */
    private LoaderHandler() {}

    
Returns an array of URLs initialized with the value of the
java.rmi.server.codebase property as the URL path.
/**
     * Returns an array of URLs initialized with the value of the
     * java.rmi.server.codebase property as the URL path.
     */
    private static synchronized URL[] getDefaultCodebaseURLs()
        throws MalformedURLException
    {
        /*
         * If it hasn't already been done, convert the codebase property
         * into an array of URLs; this may throw a MalformedURLException.
         */
        if (codebaseURLs == null) {
            if (codebaseProperty != null) {
                codebaseURLs = pathToURLs(codebaseProperty);
            } else {
                codebaseURLs = new URL[0];
            }
        }
        return codebaseURLs;
    }

    
Load a class from a network location (one or more URLs),
but first try to resolve the named class through the given
"default loader".
/**
     * Load a class from a network location (one or more URLs),
     * but first try to resolve the named class through the given
     * "default loader".
     */
    public static Class loadClass(String codebase, String name,
                                  ClassLoader defaultLoader)
        throws MalformedURLException, ClassNotFoundException
    {
        if (loaderLog.isLoggable(Log.BRIEF)) {
            loaderLog.log(Log.BRIEF,
                "name = \"" + name + "\", " +
                "codebase = \"" + (codebase != null ? codebase : "") + "\"" +
                (defaultLoader != null ?
                 ", defaultLoader = " + defaultLoader : ""));
        }

        URL[] urls;
        if (codebase != null) {
            urls = pathToURLs(codebase);
        } else {
            urls = getDefaultCodebaseURLs();
        }

        if (defaultLoader != null) {
            try {
                Class c = loadClassForName(name, false, defaultLoader);
                if (loaderLog.isLoggable(Log.VERBOSE)) {
                    loaderLog.log(Log.VERBOSE,
                        "class \"" + name + "\" found via defaultLoader, " +
                        "defined by " + c.getClassLoader());
                }
                return c;
            } catch (ClassNotFoundException e) {
            }
        }

        return loadClass(urls, name);
    }

    
Returns the class annotation (representing the location for
a class) that RMI will use to annotate the call stream when
marshalling objects of the given class.
/**
     * Returns the class annotation (representing the location for
     * a class) that RMI will use to annotate the call stream when
     * marshalling objects of the given class.
     */
    public static String getClassAnnotation(Class cl) {
        String name = cl.getName();

        /*
         * Class objects for arrays of primitive types never need an
         * annotation, because they never need to be (or can be) downloaded.
         *
         * REMIND: should we (not) be annotating classes that are in
         * "java.*" packages?
         */
        int nameLength = name.length();
        if (nameLength > 0 && name.charAt(0) == '[') {
            // skip past all '[' characters (see bugid 4211906)
            int i = 1;
            while (nameLength > i && name.charAt(i) == '[') {
                i++;
            }
            if (nameLength > i && name.charAt(i) != 'L') {
                return null;
            }
        }

        /*
         * Get the class's class loader.  If it is null, the system class
         * loader, an ancestor of the base class loader (such as the loader
         * for installed extensions), return the value of the
         * "java.rmi.server.codebase" property.
         */
        ClassLoader loader = cl.getClassLoader();
        if (loader == null || codebaseLoaders.containsKey(loader)) {
            return codebaseProperty;
        }

        /*
         * Get the codebase URL path for the class loader, if it supports
         * such a notion (i.e., if it is a URLClassLoader or subclass).
         */
        String annotation = null;
        if (loader instanceof Loader) {
            /*
             * If the class loader is one of our RMI class loaders, we have
             * already computed the class annotation string, and no
             * permissions are required to know the URLs.
             */
            annotation = ((Loader) loader).getClassAnnotation();

        } else if (loader instanceof URLClassLoader) {
            try {
                URL[] urls = ((URLClassLoader) loader).getURLs();
                if (urls != null) {
                    /*
                     * If the class loader is not one of our RMI class loaders,
                     * we must verify that the current access control context
                     * has permission to know all of these URLs.
                     */
                    SecurityManager sm = System.getSecurityManager();
                    if (sm != null) {
                        Permissions perms = new Permissions();
                        for (int i = 0; i < urls.length; i++) {
                            Permission p =
                                urls[i].openConnection().getPermission();
                            if (p != null) {
                                if (!perms.implies(p)) {
                                    sm.checkPermission(p);
                                    perms.add(p);
                                }
                            }
                        }
                    }

                    annotation = urlsToPath(urls);
                }
            } catch (SecurityException e) {
                /*
                 * If access was denied to the knowledge of the class
                 * loader's URLs, fall back to the default behavior.
                 */
            } catch (IOException e) {
                /*
                 * This shouldn't happen, although it is declared to be
                 * thrown by openConnection() and getPermission().  If it
                 * does happen, forget about this class loader's URLs and
                 * fall back to the default behavior.
                 */
            }
        }

        if (annotation != null) {
            return annotation;
        } else {
            return codebaseProperty;    // REMIND: does this make sense??
        }
    }

    
Returns a classloader that loads classes from the given codebase URL
path.  The parent classloader of the returned classloader is the
context class loader.
/**
     * Returns a classloader that loads classes from the given codebase URL
     * path.  The parent classloader of the returned classloader is the
     * context class loader.
     */
    public static ClassLoader getClassLoader(String codebase)
        throws MalformedURLException
    {
        ClassLoader parent = getRMIContextClassLoader();

        URL[] urls;
        if (codebase != null) {
            urls = pathToURLs(codebase);
        } else {
            urls = getDefaultCodebaseURLs();
        }

        /*
         * If there is a security manager, the current access control
         * context must have the "getClassLoader" RuntimePermission.
         */
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(new RuntimePermission("getClassLoader"));
        } else {
            /*
             * But if no security manager is set, disable access to
             * RMI class loaders and simply return the parent loader.
             */
            return parent;
        }

        Loader loader = lookupLoader(urls, parent);

        /*
         * Verify that the caller has permission to access this loader.
         */
        if (loader != null) {
            loader.checkPermissions();
        }

        return loader;
    }

    
Return the security context of the given class loader.
/**
     * Return the security context of the given class loader.
     */
    public static Object getSecurityContext(ClassLoader loader) {
        /*
         * REMIND: This is a bogus JDK1.1-compatible implementation.
         * This method should never be called by application code anyway
         * (hence the deprecation), but should it do something different
         * and perhaps more useful, like return a String or a URL[]?
         */
        if (loader instanceof Loader) {
            URL[] urls = ((Loader) loader).getURLs();
            if (urls.length > 0) {
                return urls[0];
            }
        }
        return null;
    }

    
Register a class loader as one whose classes should always be
annotated with the value of the "java.rmi.server.codebase" property.
/**
     * Register a class loader as one whose classes should always be
     * annotated with the value of the "java.rmi.server.codebase" property.
     */
    public static void registerCodebaseLoader(ClassLoader loader) {
        codebaseLoaders.put(loader, null);
    }

    
Load a class from the RMI class loader corresponding to the given
codebase URL path in the current execution context.
/**
     * Load a class from the RMI class loader corresponding to the given
     * codebase URL path in the current execution context.
     */
    private static Class loadClass(URL[] urls, String name)
        throws ClassNotFoundException
    {
        ClassLoader parent = getRMIContextClassLoader();
        if (loaderLog.isLoggable(Log.VERBOSE)) {
            loaderLog.log(Log.VERBOSE,
                "(thread context class loader: " + parent + ")");
        }

        /*
         * If no security manager is set, disable access to RMI class
         * loaders and simply delegate request to the parent loader
         * (see bugid 4140511).
         */
        SecurityManager sm = System.getSecurityManager();
        if (sm == null) {
            try {
                Class c = loadClassForName(name, false, parent);
                if (loaderLog.isLoggable(Log.VERBOSE)) {
                    loaderLog.log(Log.VERBOSE,
                        "class \"" + name + "\" found via " +
                        "thread context class loader " +
                        "(no security manager: codebase disabled), " +
                        "defined by " + c.getClassLoader());
                }
                return c;
            } catch (ClassNotFoundException e) {
                if (loaderLog.isLoggable(Log.BRIEF)) {
                    loaderLog.log(Log.BRIEF,
                        "class \"" + name + "\" not found via " +
                        "thread context class loader " +
                        "(no security manager: codebase disabled)", e);
                }
                throw new ClassNotFoundException(e.getMessage() +
                    " (no security manager: RMI class loader disabled)",
                    e.getException());
            }
        }

        /*
         * Get or create the RMI class loader for this codebase URL path
         * and parent class loader pair.
         */
        Loader loader = lookupLoader(urls, parent);

        try {
            if (loader != null) {
                /*
                 * Verify that the caller has permission to access this loader.
                 */
                loader.checkPermissions();
            }
        } catch (SecurityException e) {
            /*
             * If the current access control context does not have permission
             * to access all of the URLs in the codebase path, wrap the
             * resulting security exception in a ClassNotFoundException, so
             * the caller can handle this outcome just like any other class
             * loading failure (see bugid 4146529).
             */
            try {
                /*
                 * But first, check to see if the named class could have been
                 * resolved without the security-offending codebase anyway;
                 * if so, return successfully (see bugids 4191926 & 4349670).
                 */
                Class c = loadClassForName(name, false, parent);
                if (loaderLog.isLoggable(Log.VERBOSE)) {
                    loaderLog.log(Log.VERBOSE,
                        "class \"" + name + "\" found via " +
                        "thread context class loader " +
                        "(access to codebase denied), " +
                        "defined by " + c.getClassLoader());
                }
                return c;
            } catch (ClassNotFoundException unimportant) {
                /*
                 * Presumably the security exception is the more important
                 * exception to report in this case.
                 */
                if (loaderLog.isLoggable(Log.BRIEF)) {
                    loaderLog.log(Log.BRIEF,
                        "class \"" + name + "\" not found via " +
                        "thread context class loader " +
                        "(access to codebase denied)", e);
                }
                throw new ClassNotFoundException(
                    "access to class loader denied", e);
            }
        }

        try {
            Class c = loadClassForName(name, false, loader);
            if (loaderLog.isLoggable(Log.VERBOSE)) {
                loaderLog.log(Log.VERBOSE,
                    "class \"" + name + "\" " + "found via codebase, " +
                    "defined by " + c.getClassLoader());
            }
            return c;
        } catch (ClassNotFoundException e) {
            if (loaderLog.isLoggable(Log.BRIEF)) {
                loaderLog.log(Log.BRIEF,
                    "class \"" + name + "\" not found via codebase", e);
            }
            throw e;
        }
    }

    
Define and return a dynamic proxy class in a class loader with
URLs supplied in the given location.  The proxy class will
implement interface classes named by the given array of
interface names.
/**
     * Define and return a dynamic proxy class in a class loader with
     * URLs supplied in the given location.  The proxy class will
     * implement interface classes named by the given array of
     * interface names.
     */
    public static Class loadProxyClass(String codebase, String[] interfaces,
                                       ClassLoader defaultLoader)
        throws MalformedURLException, ClassNotFoundException
    {
        if (loaderLog.isLoggable(Log.BRIEF)) {
            loaderLog.log(Log.BRIEF,
                "interfaces = " + Arrays.asList(interfaces) + ", " +
                "codebase = \"" + (codebase != null ? codebase : "") + "\"" +
                (defaultLoader != null ?
                 ", defaultLoader = " + defaultLoader : ""));
        }

        /*
         * This method uses a fairly complex algorithm to load the
         * proxy class and its interface classes in order to maximize
         * the likelihood that the proxy's codebase annotation will be
         * preserved.  The algorithm is (assuming that all of the
         * proxy interface classes are public):
         *
         * If the default loader is not null, try to load the proxy
         * interfaces through that loader. If the interfaces can be
         * loaded in that loader, try to define the proxy class in an
         * RMI class loader (child of the context class loader) before
         * trying to define the proxy in the default loader.  If the
         * attempt to define the proxy class succeeds, the codebase
         * annotation is preserved.  If the attempt fails, try to
         * define the proxy class in the default loader.
         *
         * If the interface classes can not be loaded from the default
         * loader or the default loader is null, try to load them from
         * the RMI class loader.  Then try to define the proxy class
         * in the RMI class loader.
         *
         * Additionally, if any of the proxy interface classes are not
         * public, all of the non-public interfaces must reside in the
         * same class loader or it will be impossible to define the
         * proxy class (an IllegalAccessError will be thrown).  An
         * attempt to load the interfaces from the default loader is
         * made.  If the attempt fails, a second attempt will be made
         * to load the interfaces from the RMI loader. If all of the
         * non-public interfaces classes do reside in the same class
         * loader, then we attempt to define the proxy class in the
         * class loader of the non-public interfaces.  No other
         * attempt to define the proxy class will be made.
         */
        ClassLoader parent = getRMIContextClassLoader();
        if (loaderLog.isLoggable(Log.VERBOSE)) {
            loaderLog.log(Log.VERBOSE,
                "(thread context class loader: " + parent + ")");
        }

        URL[] urls;
        if (codebase != null) {
            urls = pathToURLs(codebase);
        } else {
            urls = getDefaultCodebaseURLs();
        }

        /*
         * If no security manager is set, disable access to RMI class
         * loaders and use the would-de parent instead.
         */
        SecurityManager sm = System.getSecurityManager();
        if (sm == null) {
            try {
                Class c = loadProxyClass(interfaces, defaultLoader, parent,
                                         false);
                if (loaderLog.isLoggable(Log.VERBOSE)) {
                    loaderLog.log(Log.VERBOSE,
                        "(no security manager: codebase disabled) " +
                        "proxy class defined by " + c.getClassLoader());
                }
                return c;
            } catch (ClassNotFoundException e) {
                if (loaderLog.isLoggable(Log.BRIEF)) {
                    loaderLog.log(Log.BRIEF,
                        "(no security manager: codebase disabled) " +
                        "proxy class resolution failed", e);
                }
                throw new ClassNotFoundException(e.getMessage() +
                    " (no security manager: RMI class loader disabled)",
                    e.getException());
            }
        }

        /*
         * Get or create the RMI class loader for this codebase URL path
         * and parent class loader pair.
         */
        Loader loader = lookupLoader(urls, parent);

        try {
            if (loader != null) {
                /*
                 * Verify that the caller has permission to access this loader.
                 */
                loader.checkPermissions();
            }
        } catch (SecurityException e) {
            /*
             * If the current access control context does not have permission
             * to access all of the URLs in the codebase path, wrap the
             * resulting security exception in a ClassNotFoundException, so
             * the caller can handle this outcome just like any other class
             * loading failure (see bugid 4146529).
             */
            try {
                /*
                 * But first, check to see if the proxy class could have been
                 * resolved without the security-offending codebase anyway;
                 * if so, return successfully (see bugids 4191926 & 4349670).
                 */
                Class c = loadProxyClass(interfaces, defaultLoader, parent,
                                         false);
                if (loaderLog.isLoggable(Log.VERBOSE)) {
                    loaderLog.log(Log.VERBOSE,
                        "(access to codebase denied) " +
                        "proxy class defined by " + c.getClassLoader());
                }
                return c;
            } catch (ClassNotFoundException unimportant) {
                /*
                 * Presumably the security exception is the more important
                 * exception to report in this case.
                 */
                if (loaderLog.isLoggable(Log.BRIEF)) {
                    loaderLog.log(Log.BRIEF,
                        "(access to codebase denied) " +
                        "proxy class resolution failed", e);
                }
                throw new ClassNotFoundException(
                    "access to class loader denied", e);
            }
        }

        try {
            Class c = loadProxyClass(interfaces, defaultLoader, loader, true);
            if (loaderLog.isLoggable(Log.VERBOSE)) {
                loaderLog.log(Log.VERBOSE,
                              "proxy class defined by " + c.getClassLoader());
            }
            return c;
        } catch (ClassNotFoundException e) {
            if (loaderLog.isLoggable(Log.BRIEF)) {
                loaderLog.log(Log.BRIEF,
                              "proxy class resolution failed", e);
            }
            throw e;
        }
    }

    
Define a proxy class in the default loader if appropriate.
Define the class in an RMI class loader otherwise.  The proxy
class will implement classes which are named in the supplied
interfaceNames.
/**
     * Define a proxy class in the default loader if appropriate.
     * Define the class in an RMI class loader otherwise.  The proxy
     * class will implement classes which are named in the supplied
     * interfaceNames.
     */
    private static Class loadProxyClass(String[] interfaceNames,
                                        ClassLoader defaultLoader,
                                        ClassLoader codebaseLoader,
                                        boolean preferCodebase)
        throws ClassNotFoundException
    {
        ClassLoader proxyLoader = null;
        Class[] classObjs = new Class[interfaceNames.length];
        boolean[] nonpublic = { false };

      defaultLoaderCase:
        if (defaultLoader != null) {
            try {
                proxyLoader =
                    loadProxyInterfaces(interfaceNames, defaultLoader,
                                        classObjs, nonpublic);
                if (loaderLog.isLoggable(Log.VERBOSE)) {
                    ClassLoader[] definingLoaders =
                        new ClassLoader[classObjs.length];
                    for (int i = 0; i < definingLoaders.length; i++) {
                        definingLoaders[i] = classObjs[i].getClassLoader();
                    }
                    loaderLog.log(Log.VERBOSE,
                        "proxy interfaces found via defaultLoader, " +
                        "defined by " + Arrays.asList(definingLoaders));
                }
            } catch (ClassNotFoundException e) {
                break defaultLoaderCase;
            }
            if (!nonpublic[0]) {
                if (preferCodebase) {
                    try {
                        return Proxy.getProxyClass(codebaseLoader, classObjs);
                    } catch (IllegalArgumentException e) {
                    }
                }
                proxyLoader = defaultLoader;
            }
            return loadProxyClass(proxyLoader, classObjs);
        }

        nonpublic[0] = false;
        proxyLoader = loadProxyInterfaces(interfaceNames, codebaseLoader,
                                          classObjs, nonpublic);
        if (loaderLog.isLoggable(Log.VERBOSE)) {
            ClassLoader[] definingLoaders = new ClassLoader[classObjs.length];
            for (int i = 0; i < definingLoaders.length; i++) {
                definingLoaders[i] = classObjs[i].getClassLoader();
            }
            loaderLog.log(Log.VERBOSE,
                "proxy interfaces found via codebase, " +
                "defined by " + Arrays.asList(definingLoaders));
        }
        if (!nonpublic[0]) {
            proxyLoader = codebaseLoader;
        }
        return loadProxyClass(proxyLoader, classObjs);
    }

    
Define a proxy class in the given class loader.  The proxy
class will implement the given interfaces Classes.
/**
     * Define a proxy class in the given class loader.  The proxy
     * class will implement the given interfaces Classes.
     */
    private static Class loadProxyClass(ClassLoader loader, Class[] interfaces)
        throws ClassNotFoundException
    {
        try {
            return Proxy.getProxyClass(loader, interfaces);
        } catch (IllegalArgumentException e) {
            throw new ClassNotFoundException(
                "error creating dynamic proxy class", e);
        }
    }

    /*
     * Load Class objects for the names in the interfaces array fron
     * the given class loader.
     *
     * We pass classObjs and nonpublic arrays to avoid needing a
     * multi-element return value.  nonpublic is an array to enable
     * the method to take a boolean argument by reference.
     *
     * nonpublic array is needed to signal when the return value of
     * this method should be used as the proxy class loader.  Because
     * null represents a valid class loader, that value is
     * insufficient to signal that the return value should not be used
     * as the proxy class loader.
     */
    private static ClassLoader loadProxyInterfaces(String[] interfaces,
                                                   ClassLoader loader,
                                                   Class[] classObjs,
                                                   boolean[] nonpublic)
        throws ClassNotFoundException
    {
        /* loader of a non-public interface class */
        ClassLoader nonpublicLoader = null;

        for (int i = 0; i < interfaces.length; i++) {
            Class cl =
                (classObjs[i] = loadClassForName(interfaces[i], false, loader));

            if (!Modifier.isPublic(cl.getModifiers())) {
                ClassLoader current = cl.getClassLoader();
                if (loaderLog.isLoggable(Log.VERBOSE)) {
                    loaderLog.log(Log.VERBOSE,
                        "non-public interface \"" + interfaces[i] +
                        "\" defined by " + current);
                }
                if (!nonpublic[0]) {
                    nonpublicLoader = current;
                    nonpublic[0] = true;
                } else if (current != nonpublicLoader) {
                    throw new IllegalAccessError(
                        "non-public interfaces defined in different " +
                        "class loaders");
                }
            }
        }
        return nonpublicLoader;
    }

    
Convert a string containing a space-separated list of URLs into a
corresponding array of URL objects, throwing a MalformedURLException
if any of the URLs are invalid.
/**
     * Convert a string containing a space-separated list of URLs into a
     * corresponding array of URL objects, throwing a MalformedURLException
     * if any of the URLs are invalid.
     */
    private static URL[] pathToURLs(String path)
        throws MalformedURLException
    {
        synchronized (pathToURLsCache) {
            Object[] v = pathToURLsCache.get(path);
            if (v != null) {
                return ((URL[])v[0]);
            }
        }
        StringTokenizer st = new StringTokenizer(path); // divide by spaces
        URL[] urls = new URL[st.countTokens()];
        for (int i = 0; st.hasMoreTokens(); i++) {
            urls[i] = new URL(st.nextToken());
        }
        synchronized (pathToURLsCache) {
            pathToURLsCache.put(path,
                                new Object[] {urls, new SoftReference<String>(path)});
        }
        return urls;
    }

    
map from weak(key=string) to [URL[], soft(key)] /** map from weak(key=string) to [URL[], soft(key)] */
    private static final Map<String, Object[]> pathToURLsCache
        = new WeakHashMap<String, Object[]>(5);

    
Convert an array of URL objects into a corresponding string
containing a space-separated list of URLs.
Note that if the array has zero elements, the return value is
null, not the empty string.
/**
     * Convert an array of URL objects into a corresponding string
     * containing a space-separated list of URLs.
     *
     * Note that if the array has zero elements, the return value is
     * null, not the empty string.
     */
    private static String urlsToPath(URL[] urls) {
        if (urls.length == 0) {
            return null;
        } else if (urls.length == 1) {
            return urls[0].toExternalForm();
        } else {
            StringBuffer path = new StringBuffer(urls[0].toExternalForm());
            for (int i = 1; i < urls.length; i++) {
                path.append(' ');
                path.append(urls[i].toExternalForm());
            }
            return path.toString();
        }
    }

    
Return the class loader to be used as the parent for an RMI class
loader used in the current execution context.
/**
     * Return the class loader to be used as the parent for an RMI class
     * loader used in the current execution context.
     */
    private static ClassLoader getRMIContextClassLoader() {
        /*
         * The current implementation simply uses the current thread's
         * context class loader.
         */
        return Thread.currentThread().getContextClassLoader();
    }

    
Look up the RMI class loader for the given codebase URL path
and the given parent class loader.  A new class loader instance
will be created and returned if no match is found.
/**
     * Look up the RMI class loader for the given codebase URL path
     * and the given parent class loader.  A new class loader instance
     * will be created and returned if no match is found.
     */
    private static Loader lookupLoader(final URL[] urls,
                                       final ClassLoader parent)
    {
        /*
         * If the requested codebase URL path is empty, the supplied
         * parent class loader will be sufficient.
         *
         * REMIND: To be conservative, this optimization is commented out
         * for now so that it does not open a security hole in the future
         * by providing untrusted code with direct access to the public
         * loadClass() method of a class loader instance that it cannot
         * get a reference to.  (It's an unlikely optimization anyway.)
         *
         * if (urls.length == 0) {
         *     return parent;
         * }
         */

        LoaderEntry entry;
        Loader loader;

        synchronized (LoaderHandler.class) {
            /*
             * Take this opportunity to remove from the table entries
             * whose weak references have been cleared.
             */
            while ((entry = (LoaderEntry) refQueue.poll()) != null) {
                if (!entry.removed) {   // ignore entries removed below
                    loaderTable.remove(entry.key);
                }
            }

            /*
             * Look up the codebase URL path and parent class loader pair
             * in the table of RMI class loaders.
             */
            LoaderKey key = new LoaderKey(urls, parent);
            entry = loaderTable.get(key);

            if (entry == null || (loader = entry.get()) == null) {
                /*
                 * If entry was in table but it's weak reference was cleared,
                 * remove it from the table and mark it as explicitly cleared,
                 * so that new matching entry that we put in the table will
                 * not be erroneously removed when this entry is processed
                 * from the weak reference queue.
                 */
                if (entry != null) {
                    loaderTable.remove(key);
                    entry.removed = true;
                }

                /*
                 * A matching loader was not found, so create a new class
                 * loader instance for the requested codebase URL path and
                 * parent class loader.  The instance is created within an
                 * access control context retricted to the permissions
                 * necessary to load classes from its codebase URL path.
                 */
                AccessControlContext acc = getLoaderAccessControlContext(urls);
                loader = java.security.AccessController.doPrivileged(
                    new java.security.PrivilegedAction<Loader>() {
                        public Loader run() {
                            return new Loader(urls, parent);
                        }
                    }, acc);

                /*
                 * Finally, create an entry to hold the new loader with a
                 * weak reference and store it in the table with the key.
                 */
                entry = new LoaderEntry(key, loader);
                loaderTable.put(key, entry);
            }
        }

        return loader;
    }

    
LoaderKey holds a codebase URL path and parent class loader pair
used to look up RMI class loader instances in its class loader cache.
/**
     * LoaderKey holds a codebase URL path and parent class loader pair
     * used to look up RMI class loader instances in its class loader cache.
     */
    private static class LoaderKey {

        private URL[] urls;

        private ClassLoader parent;

        private int hashValue;

        public LoaderKey(URL[] urls, ClassLoader parent) {
            this.urls = urls;
            this.parent = parent;

            if (parent != null) {
                hashValue = parent.hashCode();
            }
            for (int i = 0; i < urls.length; i++) {
                hashValue ^= urls[i].hashCode();
            }
        }

        public int hashCode() {
            return hashValue;
        }

        public boolean equals(Object obj) {
            if (obj instanceof LoaderKey) {
                LoaderKey other = (LoaderKey) obj;
                if (parent != other.parent) {
                    return false;
                }
                if (urls == other.urls) {
                    return true;
                }
                if (urls.length != other.urls.length) {
                    return false;
                }
                for (int i = 0; i < urls.length; i++) {
                    if (!urls[i].equals(other.urls[i])) {
                        return false;
                    }
                }
                return true;
            } else {
                return false;
            }
        }
    }

    
LoaderEntry contains a weak reference to an RMIClassLoader.  The
weak reference is registered with the private static "refQueue"
queue.  The entry contains the codebase URL path and parent class
loader key for the loader so that the mapping can be removed from
the table efficiently when the weak reference is cleared.
/**
     * LoaderEntry contains a weak reference to an RMIClassLoader.  The
     * weak reference is registered with the private static "refQueue"
     * queue.  The entry contains the codebase URL path and parent class
     * loader key for the loader so that the mapping can be removed from
     * the table efficiently when the weak reference is cleared.
     */
    private static class LoaderEntry extends WeakReference<Loader> {

        public LoaderKey key;

        
set to true if the entry has been removed from the table
because it has been replaced, so it should not be attempted
to be removed again
/**
         * set to true if the entry has been removed from the table
         * because it has been replaced, so it should not be attempted
         * to be removed again
         */
        public boolean removed = false;

        public LoaderEntry(LoaderKey key, Loader loader) {
            super(loader, refQueue);
            this.key = key;
        }
    }

    
Return the access control context that a loader for the given
codebase URL path should execute with.
/**
     * Return the access control context that a loader for the given
     * codebase URL path should execute with.
     */
    private static AccessControlContext getLoaderAccessControlContext(
        URL[] urls)
    {
        /*
         * The approach used here is taken from the similar method
         * getAccessControlContext() in the sun.applet.AppletPanel class.
         */
        // begin with permissions granted to all code in current policy
        PermissionCollection perms =
            java.security.AccessController.doPrivileged(
                new java.security.PrivilegedAction<PermissionCollection>() {
                public PermissionCollection run() {
                    CodeSource codesource = new CodeSource(null,
                        (java.security.cert.Certificate[]) null);
                    Policy p = java.security.Policy.getPolicy();
                    if (p != null) {
                        return p.getPermissions(codesource);
                    } else {
                        return new Permissions();
                    }
                }
            });

        // createClassLoader permission needed to create loader in context
        perms.add(new RuntimePermission("createClassLoader"));

        // add permissions to read any "java.*" property
        perms.add(new java.util.PropertyPermission("java.*","read"));

        // add permissions reuiqred to load from codebase URL path
        addPermissionsForURLs(urls, perms, true);

        /*
         * Create an AccessControlContext that consists of a single
         * protection domain with only the permissions calculated above.
         */
        ProtectionDomain pd = new ProtectionDomain(
            new CodeSource((urls.length > 0 ? urls[0] : null),
                (java.security.cert.Certificate[]) null),
            perms);
        return new AccessControlContext(new ProtectionDomain[] { pd });
    }

    
Adds to the specified permission collection the permissions
necessary to load classes from a loader with the specified URL
path; if "forLoader" is true, also adds URL-specific
permissions necessary for the security context that such a
loader operates within, such as permissions necessary for
granting automatic permissions to classes defined by the
loader.  A given permission is only added to the collection if
it is not already implied by the collection.
/**
     * Adds to the specified permission collection the permissions
     * necessary to load classes from a loader with the specified URL
     * path; if "forLoader" is true, also adds URL-specific
     * permissions necessary for the security context that such a
     * loader operates within, such as permissions necessary for
     * granting automatic permissions to classes defined by the
     * loader.  A given permission is only added to the collection if
     * it is not already implied by the collection.
     */
    private static void addPermissionsForURLs(URL[] urls,
                                              PermissionCollection perms,
                                              boolean forLoader)
    {
        for (int i = 0; i < urls.length; i++) {
            URL url = urls[i];
            try {
                URLConnection urlConnection = url.openConnection();
                Permission p = urlConnection.getPermission();
                if (p != null) {
                    if (p instanceof FilePermission) {
                        /*
                         * If the codebase is a file, the permission required
                         * to actually read classes from the codebase URL is
                         * the permission to read all files beneath the last
                         * directory in the file path, either because JAR
                         * files can refer to other JAR files in the same
                         * directory, or because permission to read a
                         * directory is not implied by permission to read the
                         * contents of a directory, which all that might be
                         * granted.
                         */
                        String path = p.getName();
                        int endIndex = path.lastIndexOf(File.separatorChar);
                        if (endIndex != -1) {
                            path = path.substring(0, endIndex+1);
                            if (path.endsWith(File.separator)) {
                                path += "-";
                            }
                            Permission p2 = new FilePermission(path, "read");
                            if (!perms.implies(p2)) {
                                perms.add(p2);
                            }
                            perms.add(new FilePermission(path, "read"));
                        } else {
                            /*
                             * No directory separator: use permission to
                             * read the file.
                             */
                            if (!perms.implies(p)) {
                                perms.add(p);
                            }
                        }
                    } else {
                        if (!perms.implies(p)) {
                            perms.add(p);
                        }

                        /*
                         * If the purpose of these permissions is to grant
                         * them to an instance of a URLClassLoader subclass,
                         * we must add permission to connect to and accept
                         * from the host of non-"file:" URLs, otherwise the
                         * getPermissions() method of URLClassLoader will
                         * throw a security exception.
                         */
                        if (forLoader) {
                            // get URL with meaningful host component
                            URL hostURL = url;
                            for (URLConnection conn = urlConnection;
                                 conn instanceof JarURLConnection;)
                            {
                                hostURL =
                                    ((JarURLConnection) conn).getJarFileURL();
                                conn = hostURL.openConnection();
                            }
                            String host = hostURL.getHost();
                            if (host != null &&
                                p.implies(new SocketPermission(host,
                                                               "resolve")))
                            {
                                Permission p2 =
                                    new SocketPermission(host,
                                                         "connect,accept");
                                if (!perms.implies(p2)) {
                                    perms.add(p2);
                                }
                            }
                        }
                    }
                }
            } catch (IOException e) {
                /*
                 * This shouldn't happen, although it is declared to be
                 * thrown by openConnection() and getPermission().  If it
                 * does, don't bother granting or requiring any permissions
                 * for this URL.
                 */
            }
        }
    }

    
Loader is the actual class of the RMI class loaders created
by the RMIClassLoader static methods.
/**
     * Loader is the actual class of the RMI class loaders created
     * by the RMIClassLoader static methods.
     */
    private static class Loader extends URLClassLoader {

        
parent class loader, kept here as an optimization /** parent class loader, kept here as an optimization */
        private ClassLoader parent;

        
string form of loader's codebase URL path, also an optimization /** string form of loader's codebase URL path, also an optimization */
        private String annotation;

        
permissions required to access loader through public API /** permissions required to access loader through public API */
        private Permissions permissions;

        private Loader(URL[] urls, ClassLoader parent) {
            super(urls, parent);
            this.parent = parent;

            /*
             * Precompute the permissions required to access the loader.
             */
            permissions = new Permissions();
            addPermissionsForURLs(urls, permissions, false);

            /*
             * Caching the value of class annotation string here assumes
             * that the protected method addURL() is never called on this
             * class loader.
             */
            annotation = urlsToPath(urls);
        }

        
Return the string to be annotated with all classes loaded from
this class loader.
/**
         * Return the string to be annotated with all classes loaded from
         * this class loader.
         */
        public String getClassAnnotation() {
            return annotation;
        }

        
Check that the current access control context has all of the
permissions necessary to load classes from this loader.
/**
         * Check that the current access control context has all of the
         * permissions necessary to load classes from this loader.
         */
        private void checkPermissions() {
            SecurityManager sm = System.getSecurityManager();
            if (sm != null) {           // should never be null?
                Enumeration enum_ = permissions.elements();
                while (enum_.hasMoreElements()) {
                    sm.checkPermission((Permission) enum_.nextElement());
                }
            }
        }

        
Return the permissions to be granted to code loaded from the
given code source.
/**
         * Return the permissions to be granted to code loaded from the
         * given code source.
         */
        protected PermissionCollection getPermissions(CodeSource codesource) {
            PermissionCollection perms = super.getPermissions(codesource);
            /*
             * Grant the same permissions that URLClassLoader would grant.
             */
            return perms;
        }

        
Return a string representation of this loader (useful for
debugging).
/**
         * Return a string representation of this loader (useful for
         * debugging).
         */
        public String toString() {
            return super.toString() + "[\"" + annotation + "\"]";
        }

        @Override
        protected Class<?> loadClass(String name, boolean resolve)
                throws ClassNotFoundException {
            if (parent == null) {
                ReflectUtil.checkPackageAccess(name);
            }
            return super.loadClass(name, resolve);
        }

    }

    private static Class<?> loadClassForName(String name,
                                              boolean initialize,
                                              ClassLoader loader)
            throws ClassNotFoundException
    {
        if (loader == null) {
            ReflectUtil.checkPackageAccess(name);
        }
        return Class.forName(name, initialize, loader);
    }

}