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 KeepAliveClass

    26  * @summary This test case uses a java.lang.Class instance to keep a class alive.

    27  * @library /testlibrary /testlibrary/whitebox /runtime/testlibrary

    28  * @library classes

    29  * @build KeepAliveClass test.Empty

    30  * @build ClassUnloadCommon

    31  * @run main ClassFileInstaller sun.hotspot.WhiteBox

    32  * @run main/othervm -Xbootclasspath/a:. -Xmn8m -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI KeepAliveClass

    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 KeepAliveClass {

    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     o = null; cl = null;

    51     escape = c;

    52 

    53     {

    54         boolean isAlive = wb.isClassAlive(className);

    55         System.out.println("testClass (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("testClass (2) alive: " + isAlive);

    65 

    66         ClassUnloadCommon.failIf(!isAlive, "should be alive");

    67     }

    68     c = null;

    69     escape = null;

    70     ClassUnloadCommon.triggerUnloading();

    71 

    72     {

    73         boolean isAlive = wb.isClassAlive(className);

    74         System.out.println("testClass (3) alive: " + isAlive);

    75         ClassUnloadCommon.failIf(isAlive, "should be unloaded");

    76     }

    77 

    78   }

    79 }