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/*
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* Copyright 2006 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Sun designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Sun in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*/
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package sun.misc;
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/**
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* Provides utility functions related to URLClassLoaders or subclasses of it.
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*
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* W A R N I N G
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*
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* This class uses undocumented, unpublished, private data structures inside
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* java.net.URLClassLoader and sun.misc.URLClassPath. Use with extreme caution.
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*
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* @author tjquinn
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*/
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import java.io.IOException;
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import java.net.URLClassLoader;
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import java.util.*;
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import java.util.jar.JarFile;
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public class ClassLoaderUtil {
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/**
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* Releases resources held by a URLClassLoader. A new classloader must
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* be created before the underlying resources can be accessed again.
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* @param classLoader the instance of URLClassLoader (or a subclass)
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*/
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public static void releaseLoader(URLClassLoader classLoader) {
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releaseLoader(classLoader, null);
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}
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/**
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* Releases resources held by a URLClassLoader. Notably, close the jars
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* opened by the loader. Initializes and updates the List of
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* jars that have been successfully closed.
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* <p>
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* @param classLoader the instance of URLClassLoader (or a subclass)
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* @param jarsClosed a List of Strings that will contain the names of jars
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* successfully closed; can be null if the caller does not need the information returned
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* @return a List of IOExceptions reporting jars that failed to close; null
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* indicates that an error other than an IOException occurred attempting to
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* release the loader; empty indicates a successful release; non-empty
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* indicates at least one error attempting to close an open jar.
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*/
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public static List<IOException> releaseLoader(URLClassLoader classLoader, List<String> jarsClosed) {
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List<IOException> ioExceptions = new LinkedList<IOException>();
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try {
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/* Records all IOExceptions thrown while closing jar files. */
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if (jarsClosed != null) {
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jarsClosed.clear();
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}
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URLClassPath ucp = SharedSecrets.getJavaNetAccess()
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.getURLClassPath(classLoader);
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ArrayList loaders = ucp.loaders;
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Stack urls = ucp.urls;
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HashMap lmap = ucp.lmap;
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/*
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*The urls variable in the URLClassPath object holds URLs that have not yet
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*been used to resolve a resource or load a class and, therefore, do
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*not yet have a loader associated with them. Clear the stack so any
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*future requests that might incorrectly reach the loader cannot be
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*resolved and cannot open a jar file after we think we've closed
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*them all.
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*/
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synchronized(urls) {
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urls.clear();
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}
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/*
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*Also clear the map of URLs to loaders so the class loader cannot use
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*previously-opened jar files - they are about to be closed.
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*/
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synchronized(lmap) {
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lmap.clear();
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}
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/*
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*The URLClassPath object's path variable records the list of all URLs that are on
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*the URLClassPath's class path. Leave that unchanged. This might
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*help someone trying to debug why a released class loader is still used.
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*Because the stack and lmap are now clear, code that incorrectly uses a
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*the released class loader will trigger an exception if the
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*class or resource would have been resolved by the class
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*loader (and no other) if it had not been released.
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*
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*The list of URLs might provide some hints to the person as to where
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*in the code the class loader was set up, which might in turn suggest
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*where in the code the class loader needs to stop being used.
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*The URLClassPath does not use the path variable to open new jar
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*files - it uses the urls Stack for that - so leaving the path variable
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*will not by itself allow the class loader to continue handling requests.
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*/
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/*
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*For each loader, close the jar file associated with that loader.
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*
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*The URLClassPath's use of loaders is sync-ed on the entire URLClassPath
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*object.
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*/
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synchronized (ucp) {
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for (Object o : loaders) {
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if (o != null) {
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/*
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*If the loader is a JarLoader inner class and its jarFile
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*field is non-null then try to close that jar file. Add
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*it to the list of closed files if successful.
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*/
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if (o instanceof URLClassPath.JarLoader) {
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URLClassPath.JarLoader jl = (URLClassPath.JarLoader)o;
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JarFile jarFile = jl.getJarFile();
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try {
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if (jarFile != null) {
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jarFile.close();
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if (jarsClosed != null) {
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jarsClosed.add(jarFile.getName());
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}
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}
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} catch (IOException ioe) {
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/*
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*Wrap the IOException to identify which jar
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*could not be closed and add it to the list
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*of IOExceptions to be returned to the caller.
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*/
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String jarFileName = (jarFile == null) ? "filename not available":jarFile.getName();
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String msg = "Error closing JAR file: " + jarFileName;
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IOException newIOE = new IOException(msg);
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newIOE.initCause(ioe);
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ioExceptions.add(newIOE);
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}
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}
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}
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}
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/*
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*Now clear the loaders ArrayList.
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*/
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loaders.clear();
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}
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} catch (Throwable t) {
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throw new RuntimeException (t);
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}
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return ioExceptions;
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}
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}
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