/* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER. * * Copyright (c) 1997-2011 Oracle and/or its affiliates. All rights reserved. * * The contents of this file are subject to the terms of either the GNU * General Public License Version 2 only ("GPL") or the Common Development * and Distribution License("CDDL") (collectively, the "License"). You * may not use this file except in compliance with the License. You can * obtain a copy of the License at * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html * or packager/legal/LICENSE.txt. See the License for the specific * language governing permissions and limitations under the License. * * When distributing the software, include this License Header Notice in each * file and include the License file at packager/legal/LICENSE.txt. * * GPL Classpath Exception: * Oracle designates this particular file as subject to the "Classpath" * exception as provided by Oracle in the GPL Version 2 section of the License * file that accompanied this code. * * Modifications: * If applicable, add the following below the License Header, with the fields * enclosed by brackets [] replaced by your own identifying information: * "Portions Copyright [year] [name of copyright owner]" * * Contributor(s): * If you wish your version of this file to be governed by only the CDDL or * only the GPL Version 2, indicate your decision by adding "[Contributor] * elects to include this software in this distribution under the [CDDL or GPL * Version 2] license." If you don't indicate a single choice of license, a * recipient has the option to distribute your version of this file under * either the CDDL, the GPL Version 2 or to extend the choice of license to * its licensees as provided above. However, if you add GPL Version 2 code * and therefore, elected the GPL Version 2 license, then the option applies * only if the new code is made subject to such option by the copyright * holder. */ package com.sun.appserv; import java.io.IOException; import java.lang.reflect.Field; import java.net.URLClassLoader; import java.util.ArrayList; import java.util.HashMap; import java.util.Stack; import java.util.Vector; import java.util.jar.JarFile; import java.util.logging.Level; import java.util.logging.Logger; import java.text.MessageFormat; import sun.misc.URLClassPath; import com.sun.logging.LogDomains; /** * 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 * * W A R N I N G * *This class uses undocumented, unpublished, private data structures inside *java.net.URLClassLoader and sun.misc.URLClassPath.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 */ public class ClassLoaderUtil { /** records whether initialization has been completed */ private static boolean isInitialized = false; /** names of classes and fields of interest for closing the loader's jar files */ private static final String URLCLASSLOADER_UCP_FIELD_NAME = "ucp"; private static final String URLCLASSPATH_LOADERS_FIELD_NAME = "loaders"; // ArrayList of URLClassPath.Loader private static final String URLCLASSPATH_URLS_FIELD_NAME = "urls"; // Stack of URL private static final String URLCLASSPATH_LMAP_FIELD_NAME = "lmap"; // HashMap of String -> URLClassPath.Loader private static final String URLCLASSPATH_JARLOADER_INNER_CLASS_NAME = "sun.misc.URLClassPath$JarLoader"; private static final String URLCLASSPATH_JARLOADER_JARFILE_FIELD_NAME = "jar"; /* Fields used during processing - they can be set up once and then used repeatedly */ private static Field jcpField; private static Field loadersField; private static Field urlsField; private static Field lmapField; private static Class jarLoaderInnerClass; private static Field jarFileField; private static boolean initDone = false; /** *Initializes the class. *

*Each utility method should invoke init() before doing their own work *to make sure the initialization is done. *@throws any Throwable detected during static init. */ private static void init() throws Throwable { if ( ! initDone) { initForClosingJars(); initDone = true; } } /** *Sets up variables used in closing a loader's jar files. *@throws NoSuchFieldException in case a field of interest is not found where expected */ private static void initForClosingJars() throws NoSuchFieldException { jcpField = getField(URLClassLoader.class, URLCLASSLOADER_UCP_FIELD_NAME); loadersField = getField(URLClassPath.class, URLCLASSPATH_LOADERS_FIELD_NAME); urlsField = getField(URLClassPath.class, URLCLASSPATH_URLS_FIELD_NAME); lmapField = getField(URLClassPath.class, URLCLASSPATH_LMAP_FIELD_NAME); jarLoaderInnerClass = getInnerClass(URLClassPath.class, URLCLASSPATH_JARLOADER_INNER_CLASS_NAME); jarFileField = getField(jarLoaderInnerClass, URLCLASSPATH_JARLOADER_JARFILE_FIELD_NAME); } /** *Retrieves a Field object for a given field on the specified class, having *set it accessible. *@param cls the Class on which the field is expected to be defined *@param fieldName the name of the field of interest *@throws NoSuchFieldException in case of any error retriving information about the field */ private static Field getField(Class cls, String fieldName) throws NoSuchFieldException { try { Field field = cls.getDeclaredField(fieldName); field.setAccessible(true); return field; } catch (NoSuchFieldException nsfe) { NoSuchFieldException e = new NoSuchFieldException(getMessage("classloaderutil.errorGettingField", fieldName)); e.initCause(nsfe); throw e; } } /** *Retrieves a given inner class definition from the specified outer class. *@param cls the outer Class *@param innerClassName the fully-qualified name of the inner class of interest */ private static Class getInnerClass(Class cls, String innerClassName) { Class result = null; Class[] innerClasses = cls.getDeclaredClasses(); for (Class c : innerClasses) { if (c.getName().equals(innerClassName)) { result = c; break; } } return result; } /** *Releases resources held by the URLClassLoader. Notably, close the jars *opened by the loader. This does not prevent the class loader from *continuing to return classes it has already resolved. *@param classLoader the instance of URLClassLoader (or a subclass) *@return array of IOExceptions reporting jars that failed to close */ public static void releaseLoader(URLClassLoader classLoader) { releaseLoader(classLoader, null); } /** *Releases resources held by the URLClassLoader. Notably, close the jars *opened by the loader. This does not prevent the class loader from *continuing to return classes it has alrady resolved although that is not *what we intend to happen. Initializes and updates the Vector of *jars that have been successfully closed. *

*Any errors are logged. *@param classLoader the instance of URLClassLoader (or a subclass) *@param jarsClosed a Vector of Strings that will contain the names of jars * successfully closed; can be null if the caller does not need the information returned *@return array 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 IOException [] releaseLoader(URLClassLoader classLoader, Vector jarsClosed) { IOException[] result = null; try { init(); /* Records all IOExceptions thrown while closing jar files. */ Vector ioExceptions = new Vector(); if (jarsClosed != null) { jarsClosed.clear(); } URLClassPath ucp = (URLClassPath) jcpField.get(classLoader); ArrayList loaders = (ArrayList) loadersField.get(ucp); Stack urls = (Stack) urlsField.get(ucp); HashMap lmap = (HashMap) lmapField.get(ucp); /* *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 (jarLoaderInnerClass.isInstance(o)) { try { JarFile jarFile = (JarFile) jarFileField.get(o); 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 msg = getMessage("classloaderutil.errorClosingJar", jarFile.getName()); IOException newIOE = new IOException(msg); newIOE.initCause(ioe); ioExceptions.add(newIOE); /* *Log the error also. */ getLogger().log(Level.WARNING, msg, ioe); } } catch (Throwable thr) { getLogger().log(Level.WARNING, "classloaderutil.errorReleasingJarNoName", thr); } } } } /* *Now clear the loaders ArrayList. */ loaders.clear(); } result = ioExceptions.toArray(new IOException[ioExceptions.size()]); } catch (Throwable thr) { getLogger().log(Level.WARNING, "classloaderutil.errorReleasingLoader", thr); result = null; } return result; } /** *Returns the logger for the common utils component. *@return the Logger for this component */ private static Logger getLogger() { return LogDomains.getLogger(ClassLoaderUtil.class, LogDomains.UTIL_LOGGER); } /** *Returns a formatted string, using the key to find the full message and *substituting any parameters. *@param key the message key with which to locate the message of interest *@param o the object(s), if any, to be substituted into the message *@return a String containing the formatted message */ private static String getMessage(String key, Object... o) { String msg = getLogger().getResourceBundle().getString(key); return MessageFormat.format(msg, o); } }