FlushClassInfoCache.java

/*
 * Copyright (c) 2020, 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.
 */

import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.net.URL;
import java.net.URLClassLoader;

/**
 * @test
 * @bug 8231454
 * @summary Tests cache cleanup by the Introspector.flushXXX()
 */
public final class FlushClassInfoCache {

    public static void main(String[] args) throws Exception {
        verify(getLoader("testClass"));
        verify(getLoader("testAll"));
        Reference<ClassLoader> loader = getLoader("test");
        // Clear the cache in com.sun.beans.introspect.ClassInfo::CACHE
        Introspector.flushCaches();
        verify(loader);
    }

    private static void verify(Reference<?> loader) throws Exception {
        int attempt = 0;
        while (loader.get() != null) {
            if (++attempt > 10) {
                throw new RuntimeException("Too many attempts: " + attempt);
            }
            // Cannot generate OOM here, it will clear the CACHE as well
            System.gc();
            Thread.sleep(1000);
            System.out.println("Not freed :(");
        }
    }

    public static void test() {
        try {
            Introspector.getBeanInfo(FlushClassInfoCache.class);
        } catch (IntrospectionException e) {
            throw new RuntimeException(e);
        }
    }

    public static void testClass() {
        try {
            Introspector.getBeanInfo(FlushClassInfoCache.class);
            // Clear the cache in com.sun.beans.introspect.ClassInfo::CACHE
            Introspector.flushFromCaches(FlushClassInfoCache.class);
        } catch (IntrospectionException e) {
            throw new RuntimeException(e);
        }
    }

    public static void testAll() {
        try {
            Introspector.getBeanInfo(FlushClassInfoCache.class);
            // Clear the cache in com.sun.beans.introspect.ClassInfo::CACHE
            Introspector.flushCaches();
        } catch (IntrospectionException e) {
            throw new RuntimeException(e);
        }
    }

    private static Reference<ClassLoader> getLoader(String m) throws Exception {
        URL url = FlushClassInfoCache.class.getProtectionDomain()
                                     .getCodeSource().getLocation();
        URLClassLoader loader = new URLClassLoader(new URL[]{url}, null);
        Class<?> cls = Class.forName("FlushClassInfoCache", true, loader);
        cls.getDeclaredMethod(m).invoke(null);
        loader.close();
        return new WeakReference<>(loader);
    }
}