1 /*
   2  * Copyright (c) 2013, 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 KeepAliveClass
  26  * @summary This test case uses a java.lang.Class instance to keep a class alive.
  27  * @modules java.base/jdk.internal.misc
  28  * @library /testlibrary /test/lib /runtime/testlibrary
  29  * @library classes
  30  * @build KeepAliveClass test.Empty
  31  * @build ClassUnloadCommon
  32  * @run main ClassFileInstaller sun.hotspot.WhiteBox
  33  *                              sun.hotspot.WhiteBox$WhiteBoxPermission
  34  * @run main/othervm -Xbootclasspath/a:. -Xmn8m -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI KeepAliveClass
  35  */
  36 
  37 import java.lang.ref.SoftReference;
  38 import sun.hotspot.WhiteBox;
  39 
  40 /**
  41  * Test that verifies that classes are not unloaded when specific types of references are kept to them.
  42  */
  43 public class KeepAliveClass {
  44   private static final String className = "test.Empty";
  45   private static final WhiteBox wb = WhiteBox.getWhiteBox();
  46   public static Object escape = null;
  47 
  48   public static void main(String... args) throws Exception {
  49     ClassLoader cl = ClassUnloadCommon.newClassLoader();
  50     Class<?> c = cl.loadClass(className);
  51     Object o = c.newInstance();
  52     o = null; cl = null;
  53     escape = c;
  54 
  55     {
  56         boolean isAlive = wb.isClassAlive(className);
  57         System.out.println("testClass (1) alive: " + isAlive);
  58 
  59         ClassUnloadCommon.failIf(!isAlive, "should be alive");
  60     }
  61 
  62     ClassUnloadCommon.triggerUnloading();
  63 
  64     {
  65         boolean isAlive = wb.isClassAlive(className);
  66         System.out.println("testClass (2) alive: " + isAlive);
  67 
  68         ClassUnloadCommon.failIf(!isAlive, "should be alive");
  69     }
  70     c = null;
  71     escape = null;
  72     ClassUnloadCommon.triggerUnloading();
  73 
  74     {
  75         boolean isAlive = wb.isClassAlive(className);
  76         System.out.println("testClass (3) alive: " + isAlive);
  77         ClassUnloadCommon.failIf(isAlive, "should be unloaded");
  78     }
  79 
  80   }
  81 }