/*
* Copyright (c) 2006, 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.misc;
/**
* Provides utility functions related to URLClassLoaders or subclasses of it.
*
* W A R N I N G
*
* This class uses undocumented, unpublished, private data structures inside
* java.net.URLClassLoader and sun.misc.URLClassPath. Use with extreme caution.
*
* @author tjquinn
*/
import java.io.IOException;
import java.net.URLClassLoader;
import java.util.*;
import java.util.jar.JarFile;
public class ClassLoaderUtil {
/**
* Releases resources held by a URLClassLoader. A new classloader must
* be created before the underlying resources can be accessed again.
* @param classLoader the instance of URLClassLoader (or a subclass)
*/
public static void releaseLoader(URLClassLoader classLoader) {
releaseLoader(classLoader, null);
}
/**
* Releases resources held by a URLClassLoader. Notably, close the jars
* opened by the loader. Initializes and updates the List of
* jars that have been successfully closed.
* <p>
* @param classLoader the instance of URLClassLoader (or a subclass)
* @param jarsClosed a List of Strings that will contain the names of jars
* successfully closed; can be null if the caller does not need the information returned
* @return a List of IOExceptions reporting jars that failed to close; null
* indicates that an error other than an IOException occurred attempting to
* release the loader; empty indicates a successful release; non-empty
* indicates at least one error attempting to close an open jar.
*/
public static List<IOException> releaseLoader(URLClassLoader classLoader, List<String> jarsClosed) {
List<IOException> ioExceptions = new LinkedList<IOException>();
try {
/* Records all IOExceptions thrown while closing jar files. */
if (jarsClosed != null) {
jarsClosed.clear();
}
URLClassPath ucp = SharedSecrets.getJavaNetAccess()
.getURLClassPath(classLoader);
ArrayList<?> loaders = ucp.loaders;
Stack<?> urls = ucp.urls;
HashMap<?,?> lmap = ucp.lmap;
/*
*The urls variable in the URLClassPath object holds URLs that have not yet
*been used to resolve a resource or load a class and, therefore, do
*not yet have a loader associated with them. Clear the stack so any
*future requests that might incorrectly reach the loader cannot be
*resolved and cannot open a jar file after we think we've closed
*them all.
*/
synchronized(urls) {
urls.clear();
}
/*
*Also clear the map of URLs to loaders so the class loader cannot use
*previously-opened jar files - they are about to be closed.
*/
synchronized(lmap) {
lmap.clear();
}
/*
*The URLClassPath object's path variable records the list of all URLs that are on
*the URLClassPath's class path. Leave that unchanged. This might
*help someone trying to debug why a released class loader is still used.
*Because the stack and lmap are now clear, code that incorrectly uses a
*the released class loader will trigger an exception if the
*class or resource would have been resolved by the class
*loader (and no other) if it had not been released.
*
*The list of URLs might provide some hints to the person as to where
*in the code the class loader was set up, which might in turn suggest
*where in the code the class loader needs to stop being used.
*The URLClassPath does not use the path variable to open new jar
*files - it uses the urls Stack for that - so leaving the path variable
*will not by itself allow the class loader to continue handling requests.
*/
/*
*For each loader, close the jar file associated with that loader.
*
*The URLClassPath's use of loaders is sync-ed on the entire URLClassPath
*object.
*/
synchronized (ucp) {
for (Object o : loaders) {
if (o != null) {
/*
*If the loader is a JarLoader inner class and its jarFile
*field is non-null then try to close that jar file. Add
*it to the list of closed files if successful.
*/
if (o instanceof URLClassPath.JarLoader) {
URLClassPath.JarLoader jl = (URLClassPath.JarLoader)o;
JarFile jarFile = jl.getJarFile();
try {
if (jarFile != null) {
jarFile.close();
if (jarsClosed != null) {
jarsClosed.add(jarFile.getName());
}
}
} catch (IOException ioe) {
/*
*Wrap the IOException to identify which jar
*could not be closed and add it to the list
*of IOExceptions to be returned to the caller.
*/
String jarFileName = (jarFile == null) ? "filename not available":jarFile.getName();
String msg = "Error closing JAR file: " + jarFileName;
IOException newIOE = new IOException(msg);
newIOE.initCause(ioe);
ioExceptions.add(newIOE);
}
}
}
}
/*
*Now clear the loaders ArrayList.
*/
loaders.clear();
}
} catch (Throwable t) {
throw new RuntimeException (t);
}
return ioExceptions;
}
}