1 /*

     2  * Copyright 2007 Sun Microsystems, Inc.  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.  Sun designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    22  * CA 95054 USA or visit www.sun.com if you need additional information or

    23  * have any questions.

    24  */

    25 

    26 package com.sun.tools.javac.file;

    27 

    28 import java.io.Closeable;

    29 import java.io.IOException;

    30 import java.lang.reflect.Field;

    31 import java.net.URL;

    32 import java.net.URLClassLoader;

    33 import java.util.ArrayList;

    34 import java.util.jar.JarFile;

    35 

    36 /**

    37  * A URLClassLoader that also implements Closeable.

    38  * Reflection is used to access internal data structures in the URLClassLoader,

    39  * since no public API exists for this purpose. Therefore this code is somewhat

    40  * fragile. Caveat emptor.

    41  * @throws Error if the internal data structures are not as expected.

    42  *

    43  *  <p><b>This is NOT part of any API supported by Sun Microsystems.  If

    44  *  you write code that depends on this, you do so at your own risk.

    45  *  This code and its internal interfaces are subject to change or

    46  *  deletion without notice.</b>

    47  */

    48 class CloseableURLClassLoader

    49         extends URLClassLoader implements Closeable {

    50     CloseableURLClassLoader(URL[] urls, ClassLoader parent) throws Error {

    51         super(urls, parent);

    52         try {

    53             getLoaders(); //proactive check that URLClassLoader is as expected

    54         } catch (Throwable t) {

    55             throw new Error("cannot create CloseableURLClassLoader", t);

    56         }

    57     }

    58 

    59     /**

    60      * Close any jar files that may have been opened by the class loader.

    61      * Reflection is used to access the jar files in the URLClassLoader's

    62      * internal data structures.

    63      * @throws java.io.IOException if the jar files cannot be found for any

    64      * reson, or if closing the jar file itself causes an IOException.

    65      */

    66     public void close() throws IOException {

    67         try {

    68             for (Object l: getLoaders()) {

    69                 if (l.getClass().getName().equals("sun.misc.URLClassPath$JarLoader")) {

    70                     Field jarField = l.getClass().getDeclaredField("jar");

    71                     JarFile jar = (JarFile) getField(l, jarField);

    72                     if (jar != null) {

    73                         //System.err.println("CloseableURLClassLoader: closing " + jar);

    74                         jar.close();

    75                     }

    76                 }

    77             }

    78         } catch (Throwable t) {

    79             IOException e = new IOException("cannot close class loader");

    80             e.initCause(t);

    81             throw e;

    82         }

    83     }

    84 

    85     private ArrayList<?> getLoaders()

    86             throws NoSuchFieldException, IllegalArgumentException, IllegalAccessException

    87     {

    88         Field ucpField = URLClassLoader.class.getDeclaredField("ucp");

    89         Object urlClassPath = getField(this, ucpField);

    90         if (urlClassPath == null)

    91             throw new AssertionError("urlClassPath not set in URLClassLoader");

    92         Field loadersField = urlClassPath.getClass().getDeclaredField("loaders");

    93         return (ArrayList<?>) getField(urlClassPath, loadersField);

    94     }

    95 

    96     private Object getField(Object o, Field f)

    97             throws IllegalArgumentException, IllegalAccessException {

    98         boolean prev = f.isAccessible();

    99         try {

   100             f.setAccessible(true);

   101             return f.get(o);

   102         } finally {

   103             f.setAccessible(prev);

   104         }

   105     }

   106 

   107 }