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 KeepAliveObject
  26  * @summary This test case uses a class instance to keep the class alive.
  27  * @library /testlibrary /../../test/lib /runtime/testlibrary
  28  * @library classes
  29  * @build KeepAliveObject test.Empty
  30  * @build ClassUnloadCommon
  31  * @run main ClassFileInstaller jdk.testlib.WhiteBox
  32  *                              jdk.testlib.WhiteBox$WhiteBoxPermission
  33  * @run main/othervm -Xbootclasspath/a:. -Xmn8m -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI KeepAliveObject
  34  */
  35 
  36 import jdk.testlib.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 KeepAliveObject {
  42   private static final String className = "test.Empty";
  43   private static final WhiteBox wb = WhiteBox.getWhiteBox();
  44   public static Object escape = null;
  45 
  46   public static void main(String... args) throws Exception {
  47     ClassLoader cl = ClassUnloadCommon.newClassLoader();
  48     Class<?> c = cl.loadClass(className);
  49     Object o = c.newInstance();
  50     cl = null; c = null;
  51     escape = o;
  52 
  53     {
  54         boolean isAlive = wb.isClassAlive(className);
  55         System.out.println("testObject (1) alive: " + isAlive);
  56 
  57         ClassUnloadCommon.failIf(!isAlive, "should be alive");
  58     }
  59 
  60     ClassUnloadCommon.triggerUnloading();
  61 
  62     {
  63         boolean isAlive = wb.isClassAlive(className);
  64         System.out.println("testObject (2) alive: " + isAlive);
  65 
  66         ClassUnloadCommon.failIf(!isAlive, "should be alive");
  67     }
  68     o = null;
  69     escape = null;
  70     ClassUnloadCommon.triggerUnloading();
  71 
  72     {
  73         boolean isAlive = wb.isClassAlive(className);
  74         System.out.println("testObject (3) alive: " + isAlive);
  75         ClassUnloadCommon.failIf(isAlive, "should be unloaded");
  76     }
  77 
  78   }
  79 }