1 /*
   2  * Copyright (c) 2013, 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 
  24 /*
  25  * @test KeepAliveSoftReference
  26  * @summary This test case uses a java.lang.ref.SoftReference referencing a class instance to keep a class alive.
  27  * @library /testlibrary /testlibrary/whitebox /runtime/testlibrary
  28  * @library classes
  29  * @build KeepAliveSoftReference test.Empty
  30  * @build ClassUnloadCommon
  31  * @run main ClassFileInstaller sun.hotspot.WhiteBox
  32  * @run main/othervm -Xbootclasspath/a:. -Xmn8m -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI KeepAliveSoftReference
  33  */
  34 
  35 import java.lang.ref.SoftReference;
  36 import sun.hotspot.WhiteBox;
  37 
  38 /**
  39  * Test that verifies that classes are not unloaded when specific types of references are kept to them.
  40  */
  41 public class KeepAliveSoftReference {
  42   private static final String className = "test.Empty";
  43   private static final WhiteBox wb = WhiteBox.getWhiteBox();
  44 
  45   public static void main(String... args) throws Exception {
  46     ClassLoader cl = ClassUnloadCommon.newClassLoader();
  47     Class<?> c = cl.loadClass(className);
  48     Object o = c.newInstance();
  49     SoftReference<Object> sr = new SoftReference(o);
  50     o = null; c = null; cl = null;
  51 
  52     {
  53         boolean isAlive = wb.isClassAlive(className);
  54         System.out.println("testSoftReference (1) alive: " + isAlive);
  55         boolean cleared = (sr.get() == null);
  56         boolean shouldBeAlive = !cleared;
  57         ClassUnloadCommon.failIf(isAlive != shouldBeAlive, "" + isAlive + " != " + shouldBeAlive);
  58     }
  59 
  60     ClassUnloadCommon.triggerUnloading();
  61 
  62     {
  63         boolean isAlive = wb.isClassAlive(className);
  64         System.out.println("testSoftReference (2) alive: " + isAlive);
  65         boolean cleared = (sr.get() == null);
  66         boolean shouldBeAlive = !cleared;
  67         ClassUnloadCommon.failIf(isAlive != shouldBeAlive, "" + isAlive + " != " + shouldBeAlive);
  68     }
  69     sr.clear();
  70     ClassUnloadCommon.triggerUnloading();
  71 
  72     {
  73         boolean isAlive = wb.isClassAlive(className);
  74         System.out.println("testSoftReference (3) alive: " + isAlive);
  75         boolean cleared = (sr.get() == null);
  76         boolean shouldBeAlive = !cleared;
  77         ClassUnloadCommon.failIf(isAlive != shouldBeAlive, "" + isAlive + " != " + shouldBeAlive);
  78     }
  79   }
  80 }