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 }