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 }