1 /* 2 * Copyright (c) 2016, 2018, 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package jdk.jfr.internal; 26 27 import java.io.IOException; 28 29 /** 30 * Checks if the running VM supports Flight Recorder. 31 * 32 * Purpose of this helper class is to detect early and cleanly if the VM has 33 * support for Flight Recorder, i.e. not throw {@link UnsatisfiedLinkError} in 34 * unexpected places. 35 * <p> 36 * This is needed so a disabled-jfr.jar can be built for non Oracle JDKs. 37 */ 38 public final class JVMSupport { 39 40 private static final String UNSUPPORTED_VM_MESSAGE = "Flight Recorder is not supported on this VM"; 41 private static final boolean notAvailable = !checkAvailability(); 42 43 private static boolean checkAvailability() { 44 // set jfr.unsupported.vm to true to test API on an unsupported VM 45 try { 46 if (SecuritySupport.getBooleanProperty("jfr.unsupported.vm")) { 47 return false; 48 } 49 } catch (NoClassDefFoundError cnfe) { 50 // May happen on JDK 8, where jdk.internal.misc.Unsafe can't be found 51 return false; 52 } 53 try { 54 // Will typically throw UnsatisfiedLinkError if 55 // there is no native implementation 56 JVM.getJVM().isAvailable(); 57 return true; 58 } catch (Throwable t) { 59 return false; 60 } 61 } 62 63 public static void ensureWithInternalError() { 64 if (notAvailable) { 65 throw new InternalError(UNSUPPORTED_VM_MESSAGE); 66 } 67 } 68 69 public static void ensureWithIOException() throws IOException { 70 if (notAvailable) { 71 throw new IOException(UNSUPPORTED_VM_MESSAGE); 72 } 73 } 74 75 public static void ensureWithIllegalStateException() { 76 if (notAvailable) { 77 throw new IllegalStateException(UNSUPPORTED_VM_MESSAGE); 78 } 79 } 80 81 public static boolean isNotAvailable() { 82 return notAvailable; 83 } 84 }