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| 1 | +/* | |
| 2 | + * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved. | |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 4 | + * | |
| 5 | + * This code is free software; you can redistribute it and/or modify it | |
| 6 | + * under the terms of the GNU General Public License version 2 only, as | |
| 7 | + * published by the Free Software Foundation. Oracle designates this | |
| 8 | + * particular file as subject to the "Classpath" exception as provided | |
| 9 | + * by Oracle in the LICENSE file that accompanied this code. | |
| 10 | + * | |
| 11 | + * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 12 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 | + * version 2 for more details (a copy is included in the LICENSE file that | |
| 15 | + * accompanied this code). | |
| 16 | + * | |
| 17 | + * You should have received a copy of the GNU General Public License version | |
| 18 | + * 2 along with this work; if not, write to the Free Software Foundation, | |
| 19 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 20 | + * | |
| 21 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 22 | + * or visit www.oracle.com if you need additional information or have any | |
| 23 | + * questions. | |
| 24 | + */ | |
| 25 | + | |
| 26 | +package sun.misc; | |
| 27 | + | |
| 28 | +/** | |
| 29 | + * Provides utility functions related to URLClassLoaders or subclasses of it. | |
| 30 | + * | |
| 31 | + * W A R N I N G | |
| 32 | + * | |
| 33 | + * This class uses undocumented, unpublished, private data structures inside | |
| 34 | + * java.net.URLClassLoader and sun.misc.URLClassPath. Use with extreme caution. | |
| 35 | + * | |
| 36 | + * @author tjquinn | |
| 37 | + */ | |
| 38 | + | |
| 39 | + | |
| 40 | +import java.io.IOException; | |
| 41 | +import java.net.URLClassLoader; | |
| 42 | +import java.util.*; | |
| 43 | +import java.util.jar.JarFile; | |
| 44 | + | |
| 45 | +public class ClassLoaderUtil { | |
| 46 | + | |
| 47 | + /** | |
| 48 | + * Releases resources held by a URLClassLoader. A new classloader must | |
| 49 | + * be created before the underlying resources can be accessed again. | |
| 50 | + * @param classLoader the instance of URLClassLoader (or a subclass) | |
| 51 | + */ | |
| 52 | + public static void releaseLoader(URLClassLoader classLoader) { | |
| 53 | + releaseLoader(classLoader, null); | |
| 54 | + } | |
| 55 | + | |
| 56 | + /** | |
| 57 | + * Releases resources held by a URLClassLoader. Notably, close the jars | |
| 58 | + * opened by the loader. Initializes and updates the List of | |
| 59 | + * jars that have been successfully closed. | |
| 60 | + * <p> | |
| 61 | + * @param classLoader the instance of URLClassLoader (or a subclass) | |
| 62 | + * @param jarsClosed a List of Strings that will contain the names of jars | |
| 63 | + * successfully closed; can be null if the caller does not need the information returned | |
| 64 | + * @return a List of IOExceptions reporting jars that failed to close; null | |
| 65 | + * indicates that an error other than an IOException occurred attempting to | |
| 66 | + * release the loader; empty indicates a successful release; non-empty | |
| 67 | + * indicates at least one error attempting to close an open jar. | |
| 68 | + */ | |
| 69 | + public static List<IOException> releaseLoader(URLClassLoader classLoader, List<String> jarsClosed) { | |
| 70 | + | |
| 71 | + List<IOException> ioExceptions = new LinkedList<IOException>(); | |
| 72 | + | |
| 73 | + try { | |
| 74 | + /* Records all IOExceptions thrown while closing jar files. */ | |
| 75 | + | |
| 76 | + if (jarsClosed != null) { | |
| 77 | + jarsClosed.clear(); | |
| 78 | + } | |
| 79 | + | |
| 80 | + URLClassPath ucp = SharedSecrets.getJavaNetAccess() | |
| 81 | + .getURLClassPath(classLoader); | |
| 82 | + ArrayList loaders = ucp.loaders; | |
| 83 | + Stack urls = ucp.urls; | |
| 84 | + HashMap lmap = ucp.lmap; | |
| 85 | + | |
| 86 | + /* | |
| 87 | + *The urls variable in the URLClassPath object holds URLs that have not yet | |
| 88 | + *been used to resolve a resource or load a class and, therefore, do | |
| 89 | + *not yet have a loader associated with them. Clear the stack so any | |
| 90 | + *future requests that might incorrectly reach the loader cannot be | |
| 91 | + *resolved and cannot open a jar file after we think we've closed | |
| 92 | + *them all. | |
| 93 | + */ | |
| 94 | + synchronized(urls) { | |
| 95 | + urls.clear(); | |
| 96 | + } | |
| 97 | + | |
| 98 | + /* | |
| 99 | + *Also clear the map of URLs to loaders so the class loader cannot use | |
| 100 | + *previously-opened jar files - they are about to be closed. | |
| 101 | + */ | |
| 102 | + synchronized(lmap) { | |
| 103 | + lmap.clear(); | |
| 104 | + } | |
| 105 | + | |
| 106 | + /* | |
| 107 | + *The URLClassPath object's path variable records the list of all URLs that are on | |
| 108 | + *the URLClassPath's class path. Leave that unchanged. This might | |
| 109 | + *help someone trying to debug why a released class loader is still used. | |
| 110 | + *Because the stack and lmap are now clear, code that incorrectly uses a | |
| 111 | + *the released class loader will trigger an exception if the | |
| 112 | + *class or resource would have been resolved by the class | |
| 113 | + *loader (and no other) if it had not been released. | |
| 114 | + * | |
| 115 | + *The list of URLs might provide some hints to the person as to where | |
| 116 | + *in the code the class loader was set up, which might in turn suggest | |
| 117 | + *where in the code the class loader needs to stop being used. | |
| 118 | + *The URLClassPath does not use the path variable to open new jar | |
| 119 | + *files - it uses the urls Stack for that - so leaving the path variable | |
| 120 | + *will not by itself allow the class loader to continue handling requests. | |
| 121 | + */ | |
| 122 | + | |
| 123 | + /* | |
| 124 | + *For each loader, close the jar file associated with that loader. | |
| 125 | + * | |
| 126 | + *The URLClassPath's use of loaders is sync-ed on the entire URLClassPath | |
| 127 | + *object. | |
| 128 | + */ | |
| 129 | + synchronized (ucp) { | |
| 130 | + for (Object o : loaders) { | |
| 131 | + if (o != null) { | |
| 132 | + /* | |
| 133 | + *If the loader is a JarLoader inner class and its jarFile | |
| 134 | + *field is non-null then try to close that jar file. Add | |
| 135 | + *it to the list of closed files if successful. | |
| 136 | + */ | |
| 137 | + if (o instanceof URLClassPath.JarLoader) { | |
| 138 | + URLClassPath.JarLoader jl = (URLClassPath.JarLoader)o; | |
| 139 | + JarFile jarFile = jl.getJarFile(); | |
| 140 | + try { | |
| 141 | + if (jarFile != null) { | |
| 142 | + jarFile.close(); | |
| 143 | + if (jarsClosed != null) { | |
| 144 | + jarsClosed.add(jarFile.getName()); | |
| 145 | + } | |
| 146 | + } | |
| 147 | + } catch (IOException ioe) { | |
| 148 | + /* | |
| 149 | + *Wrap the IOException to identify which jar | |
| 150 | + *could not be closed and add it to the list | |
| 151 | + *of IOExceptions to be returned to the caller. | |
| 152 | + */ | |
| 153 | + String jarFileName = (jarFile == null) ? "filename not available":jarFile.getName(); | |
| 154 | + String msg = "Error closing JAR file: " + jarFileName; | |
| 155 | + IOException newIOE = new IOException(msg); | |
| 156 | + newIOE.initCause(ioe); | |
| 157 | + ioExceptions.add(newIOE); | |
| 158 | + } | |
| 159 | + } | |
| 160 | + } | |
| 161 | + } | |
| 162 | + /* | |
| 163 | + *Now clear the loaders ArrayList. | |
| 164 | + */ | |
| 165 | + loaders.clear(); | |
| 166 | + } | |
| 167 | + } catch (Throwable t) { | |
| 168 | + throw new RuntimeException (t); | |
| 169 | + } | |
| 170 | + return ioExceptions; | |
| 171 | + } | |
| 172 | +} | |