1 /*
   2  * Copyright (c) 2014, 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/othervm/bootclasspath -Xmn8m -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI KeepAliveSoftReference
  32  */
  33 
  34 import java.lang.ref.SoftReference;
  35 import sun.hotspot.WhiteBox;
  36 
  37 /**
  38  * Test that verifies that classes are not unloaded when specific types of references are kept to them.
  39  */
  40 public class KeepAliveSoftReference {
  41   private static final String className = "test.Empty";
  42   private static final WhiteBox wb = WhiteBox.getWhiteBox();
  43 
  44   public static void main(String... args) throws Exception {
  45     ClassLoader cl = ClassUnloadCommon.newClassLoader();
  46     Class<?> c = cl.loadClass(className);
  47     Object o = c.newInstance();
  48     SoftReference<Object> sr = new SoftReference(o);
  49     o = null; c = null; cl = null;
  50 
  51     {
  52         boolean isAlive = wb.isClassAlive(className);
  53         System.out.println("testSoftReference (1) alive: " + isAlive);
  54         boolean cleared = (sr.get() == null);
  55         boolean shouldBeAlive = !cleared;
  56         ClassUnloadCommon.failIf(isAlive != shouldBeAlive, "" + isAlive + " != " + shouldBeAlive);
  57     }
  58 
  59     ClassUnloadCommon.triggerUnloading();
  60 
  61     {
  62         boolean isAlive = wb.isClassAlive(className);
  63         System.out.println("testSoftReference (2) alive: " + isAlive);
  64         boolean cleared = (sr.get() == null);
  65         boolean shouldBeAlive = !cleared;
  66         ClassUnloadCommon.failIf(isAlive != shouldBeAlive, "" + isAlive + " != " + shouldBeAlive);
  67     }
  68     sr.clear();
  69     ClassUnloadCommon.triggerUnloading();
  70 
  71     {
  72         boolean isAlive = wb.isClassAlive(className);
  73         System.out.println("testSoftReference (3) alive: " + isAlive);
  74         boolean cleared = (sr.get() == null);
  75         boolean shouldBeAlive = !cleared;
  76         ClassUnloadCommon.failIf(isAlive != shouldBeAlive, "" + isAlive + " != " + shouldBeAlive);
  77     }
  78   }
  79 }