1 /*
 2  * Copyright (c) 2022, 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 
26 import java.lang.invoke.MethodHandle;
27 import java.lang.invoke.MethodHandles;
28 import java.lang.invoke.MethodType;
29 import java.util.ArrayList;
30 import java.util.List;
31 import java.util.concurrent.ThreadFactory;
32 
33 public class Virtual implements ThreadFactory {
34 
35     static {
36         // This property is used by ProcessTools and some tests
37         // Should be set for all tests
38         try {
39             System.setProperty("main.wrapper", "Virtual");
40         } catch (Throwable t) {
41         // Might be securty-related exceptions
42         }
43     }
44 
45     private ThreadFactory factory;
46 
47     public Virtual() {
48         try {
49             factory = VirtualAPI.factory();
50         } catch (Throwable t) {
51             factory = task -> new Thread(task);
52         }
53     }
54 
55 
56     @Override
57     public Thread newThread(Runnable task) {
58         try {
59             return factory.newThread(task);
60         } catch (Throwable t) {
61             throw new RuntimeException(t);
62         }
63     }
64 }
65 
66 class VirtualAPI {
67 
68     private MethodHandles.Lookup publicLookup = MethodHandles.publicLookup();
69 
70     private ThreadFactory virtualThreadFactory;
71 
72 
73     VirtualAPI() {
74         try {
75             Class<?> vbuilderClass = Class.forName("java.lang.Thread$Builder$OfVirtual");
76             MethodType vofMT = MethodType.methodType(vbuilderClass);
77             MethodHandle ofVirtualMH =  publicLookup.findStatic(Thread.class, "ofVirtual", vofMT);
78             Object virtualBuilder = ofVirtualMH.invoke();
79             MethodType factoryMT = MethodType.methodType(ThreadFactory.class);
80             MethodHandle vfactoryMH =  publicLookup.findVirtual(vbuilderClass, "factory", factoryMT);
81             virtualThreadFactory = (ThreadFactory) vfactoryMH.invoke(virtualBuilder);
82         } catch (Throwable t) {
83             throw new RuntimeException(t);
84         }
85     }
86 
87     private static VirtualAPI instance = new VirtualAPI();
88 
89     public static ThreadFactory factory() {
90         return instance.virtualThreadFactory;
91     }
92 }