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 }