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. 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 package jdk.vm.ci.services; 24 25 import java.util.ArrayList; 26 import java.util.List; 27 import java.util.ServiceLoader; 28 29 /** 30 * Service-provider class for the runtime to locate providers of JVMCI services where the latter are 31 * not in packages exported by the JVMCI module. As part of instantiating a 32 * {@link JVMCIServiceLocator}, all JVMCI packages will be opened to the module defining the class 33 * of the instantiated object. 34 * 35 * While the {@link #getProvider(Class)} method can be used directly, it's usually easier to use 36 * {@link #getProviders(Class)}. 37 */ 38 public abstract class JVMCIServiceLocator { 39 40 private static Void checkPermission() { 41 SecurityManager sm = System.getSecurityManager(); 42 if (sm != null) { 43 sm.checkPermission(new JVMCIPermission()); 44 } 45 return null; 46 } 47 48 @SuppressWarnings("unused") 49 private JVMCIServiceLocator(Void ignore) { 50 } 51 52 /** 53 * Creates a capability for accessing JVMCI. Once successfully instantiated, JVMCI opens all its 54 * packages to the module defining the type of this object. 55 * 56 * @throws SecurityException if a security manager has been installed and it denies 57 * {@link JVMCIPermission} 58 */ 59 protected JVMCIServiceLocator() { 60 this(checkPermission()); 61 Services.checkJVMCIEnabled(); 62 Services.openJVMCITo(getClass().getModule()); 63 } 64 65 /** 66 * Gets the provider of the service defined by {@code service} or {@code null} if this object 67 * does not have a provider for {@code service}. 68 */ 69 protected abstract <S> S getProvider(Class<S> service); 70 71 /** 72 * Gets the providers of the service defined by {@code service} by querying the available 73 * {@link JVMCIServiceLocator} providers. 74 * 75 * @throws SecurityException if a security manager is present and it denies 76 * {@link JVMCIPermission} 77 */ 78 public static <S> List<S> getProviders(Class<S> service) { 79 Services.checkJVMCIEnabled(); 80 SecurityManager sm = System.getSecurityManager(); 81 if (sm != null) { 82 sm.checkPermission(new JVMCIPermission()); 83 } 84 List<S> providers = new ArrayList<>(); 85 for (JVMCIServiceLocator access : ServiceLoader.load(JVMCIServiceLocator.class, ClassLoader.getSystemClassLoader())) { 86 S provider = access.getProvider(service); 87 if (provider != null) { 88 providers.add(provider); 89 } 90 } 91 return providers; 92 } 93 }