jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/util/CloseableURLClassLoader.java@4011f49b4af8

     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  */

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

    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;

    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 public class CloseableURLClassLoader

    49         extends URLClassLoader implements Closeable {

    50     public 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     }

    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     @Override

    67     public void close() throws IOException {

    68         try {

    69             for (Object l: getLoaders()) {

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

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

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

    73                     if (jar != null) {

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

    75                         jar.close();

    76                     }

    77                 }

    78             }

    79         } catch (Throwable t) {

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

    81             e.initCause(t);

    82             throw e;

    83         }

    84     }

    86     private ArrayList<?> getLoaders()

    87             throws NoSuchFieldException, IllegalArgumentException, IllegalAccessException

    88     {

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

    90         Object urlClassPath = getField(this, ucpField);

    91         if (urlClassPath == null)

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

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

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

    95     }

    97     private Object getField(Object o, Field f)

    98             throws IllegalArgumentException, IllegalAccessException {

    99         boolean prev = f.isAccessible();

   100         try {

   101             f.setAccessible(true);

   102             return f.get(o);

   103         } finally {

   104             f.setAccessible(prev);

   105         }

   106     }

   108 }

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