rev 59093 : imported patch randomness-code_vmTestbase_unloading

   1 /*
   2  * Copyright (c) 2014, 2018, 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.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 package gc.g1.unloading.keepref;
  24 
  25 import java.lang.reflect.*;
  26 import java.util.*;
  27 
  28 /**
  29  * This holder keeps class from being collected by saving link in static field of class loaded by null classloader.
  30  * It uses pool of classes that should reside in bootclasspath.
  31  */
  32 public class NullClassloaderHolder implements RefHolder {
  33 
  34     private static final int NUMBER_OF_CLASSES = 1000;
  35     private static Set<Class<?>> classesPool = Collections.synchronizedSet(new HashSet<Class<?>>());

  36 
  37     static {
  38         for (int i = 1; i <= NUMBER_OF_CLASSES; i++) {
  39             String className = "gc.g1.unloading.rootSetHelper.classesPool.Class" + i;
  40             try {
  41                 Class<?> clazz = Class.forName(className);
  42                 if (clazz.getClassLoader() != null) {
  43                     throw new RuntimeException("Test bug! Classes from pool implied to be loaded by bootclassloader.");
  44                 }
  45                 classesPool.add(clazz);
  46             } catch (ClassNotFoundException e) {
  47                 throw new RuntimeException("Test bug", e);
  48             }
  49         }
  50     }
  51 




  52     @Override
  53     public Object hold(Object object) {
  54         if (classesPool.isEmpty()) {
  55             return null;
  56         } else {
  57             Class<?> clazz = (Class<?>) classesPool.iterator().next();
  58             classesPool.remove(clazz);
  59             Field f = getRandomField(clazz);
  60             try {
  61                 f.set(null, object);
  62                 return clazz.newInstance();
  63             } catch (IllegalArgumentException | IllegalAccessException | InstantiationException e) {
  64                 throw new RuntimeException("Test bug", e);
  65             }
  66         }
  67     }
  68 
  69     private static Field getRandomField(Class<?> clazz) {
  70         ArrayList<Field> fields = new ArrayList<>();
  71         for (Field f : clazz.getFields()) {
  72             if (f.getName().startsWith("staticField")) {
  73                 fields.add(f);
  74             }
  75         }
  76         return fields.get(new Random().nextInt(fields.size()));
  77     }
  78 
  79 }
--- EOF ---