| /* |
| * Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| package gc.g1.unloading.keepref; |
| |
| import java.lang.reflect.*; |
| import java.util.*; |
| |
| /** |
| * This holder keeps class from being collected by saving link in static field of class loaded by null classloader. |
| * It uses pool of classes that should reside in bootclasspath. |
| */ |
| public class NullClassloaderHolder implements RefHolder { |
| |
| private static final int NUMBER_OF_CLASSES = 1000; |
| private static Set<Class<?>> classesPool = Collections.synchronizedSet(new HashSet<Class<?>>()); |
| |
| static { |
| for (int i = 1; i <= NUMBER_OF_CLASSES; i++) { |
| String className = "gc.g1.unloading.rootSetHelper.classesPool.Class" + i; |
| try { |
| Class<?> clazz = Class.forName(className); |
| if (clazz.getClassLoader() != null) { |
| throw new RuntimeException("Test bug! Classes from pool implied to be loaded by bootclassloader."); |
| } |
| classesPool.add(clazz); |
| } catch (ClassNotFoundException e) { |
| throw new RuntimeException("Test bug", e); |
| } |
| } |
| } |
| |
| @Override |
| public Object hold(Object object) { |
| if (classesPool.isEmpty()) { |
| return null; |
| } else { |
| Class<?> clazz = (Class<?>) classesPool.iterator().next(); |
| classesPool.remove(clazz); |
| Field f = getRandomField(clazz); |
| try { |
| f.set(null, object); |
| return clazz.newInstance(); |
| } catch (IllegalArgumentException | IllegalAccessException | InstantiationException e) { |
| throw new RuntimeException("Test bug", e); |
| } |
| } |
| } |
| |
| private static Field getRandomField(Class<?> clazz) { |
| ArrayList<Field> fields = new ArrayList<>(); |
| for (Field f : clazz.getFields()) { |
| if (f.getName().startsWith("staticField")) { |
| fields.add(f); |
| } |
| } |
| return fields.get(new Random().nextInt(fields.size())); |
| } |
| |
| } |