85 lines
3.1 KiB
Java
85 lines
3.1 KiB
Java
/*
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* Copyright (c) 2014, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package gc.g1.unloading.keepref;
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import java.lang.reflect.*;
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import java.util.*;
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/**
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* This holder keeps class from being collected by saving link in static field of class loaded by null classloader.
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* It uses pool of classes that should reside in bootclasspath.
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*/
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public class NullClassloaderHolder implements RefHolder {
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private static final int NUMBER_OF_CLASSES = 1000;
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private static Set<Class<?>> classesPool = Collections.synchronizedSet(new HashSet<Class<?>>());
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private final Random random;
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static {
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for (int i = 1; i <= NUMBER_OF_CLASSES; i++) {
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String className = "gc.g1.unloading.rootSetHelper.classesPool.Class" + i;
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try {
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Class<?> clazz = Class.forName(className);
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if (clazz.getClassLoader() != null) {
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throw new RuntimeException("Test bug! Classes from pool implied to be loaded by bootclassloader.");
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}
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classesPool.add(clazz);
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} catch (ClassNotFoundException e) {
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throw new RuntimeException("Test bug", e);
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}
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}
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}
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public NullClassloaderHolder(long seed) {
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random = new Random(seed);
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}
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@Override
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public Object hold(Object object) {
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if (classesPool.isEmpty()) {
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return null;
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} else {
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Class<?> clazz = (Class<?>) classesPool.iterator().next();
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classesPool.remove(clazz);
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Field f = getRandomField(clazz);
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try {
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f.set(null, object);
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return clazz.newInstance();
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} catch (IllegalArgumentException | IllegalAccessException | InstantiationException e) {
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throw new RuntimeException("Test bug", e);
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}
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}
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}
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private Field getRandomField(Class<?> clazz) {
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ArrayList<Field> fields = new ArrayList<>();
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for (Field f : clazz.getFields()) {
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if (f.getName().startsWith("staticField")) {
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fields.add(f);
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}
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}
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return fields.get(random.nextInt(fields.size()));
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}
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}
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