Java example source code file (LoaderHandler.java)
The LoaderHandler.java Java example source code/*
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* 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
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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;
/**
* <code>LoaderHandler provides the implementation of the static
* methods of the <code>java.rmi.server.RMIClassLoader class.
*
* @author Ann Wollrath
* @author Peter Jones
* @author Laird Dornin
*/
@SuppressWarnings("deprecation")
public final class LoaderHandler {
/** 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.
*/
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 */
private static URL[] codebaseURLs = null;
/** 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.
*/
private static final HashMap<LoaderKey, LoaderEntry> loaderTable
= new HashMap<>(5);
/** reference queue for cleared class loader entries */
private static final ReferenceQueue<Loader> refQueue
= new ReferenceQueue<>();
/*
* 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.
*/
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".
*/
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.
*/
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 | IOException e) {
/*
* SecurityException: If access was denied to the knowledge of
* the class loader's URLs, fall back to the default behavior.
*
* IOException: 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.
*/
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.
*/
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.
*/
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.
*/
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 = Class.forName(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.
*/
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.
*/
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.
*/
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.
*/
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)] */
private static final Map<String, Object[]> pathToURLsCache
= new WeakHashMap<>(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.
*/
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.
*/
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.
*/
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.
*/
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.
*/
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
*/
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.
*/
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.
*/
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.
*/
private static class Loader extends URLClassLoader {
/** parent class loader, kept here as an optimization */
private ClassLoader parent;
/** string form of loader's codebase URL path, also an optimization */
private String annotation;
/** 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.
*/
public String getClassAnnotation() {
return annotation;
}
/**
* 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<Permission> enum_ = permissions.elements();
while (enum_.hasMoreElements()) {
sm.checkPermission(enum_.nextElement());
}
}
}
/**
* 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).
*/
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);
}
}
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