001/*
002 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.
008 *
009 * This code is distributed in the hope that it will be useful, but WITHOUT
010 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
011 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
012 * version 2 for more details (a copy is included in the LICENSE file that
013 * accompanied this code).
014 *
015 * You should have received a copy of the GNU General Public License version
016 * 2 along with this work; if not, write to the Free Software Foundation,
017 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
018 *
019 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
020 * or visit www.oracle.com if you need additional information or have any
021 * questions.
022 */
023package jdk.internal.jvmci.service;
024
025import java.util.*;
026
027import sun.reflect.*;
028
029/**
030 * An mechanism for accessing service providers via JVMCI. These providers are loaded via a JVMCI
031 * class loader that is hidden from application code. Hence the {@link SecurityManager} checks in
032 * {@link #load(Class)} and {@link #loadSingle(Class, boolean)}.
033 */
034public final class Services {
035
036    private Services() {
037    }
038
039    private static final String SUPPRESS_PROPERTY_NAME = "jvmci.service.suppressNoClassDefFoundError";
040
041    /**
042     * Determines whether to suppress the {@link NoClassDefFoundError} raised if a service provider
043     * class specified in a {@code <jre>/jvmci/services/*} file is missing.
044     */
045    private static final boolean SuppressNoClassDefFoundError = Boolean.getBoolean(SUPPRESS_PROPERTY_NAME);
046
047    private static final ClassValue<List<?>> cache = new ClassValue<List<?>>() {
048        @Override
049        protected List<?> computeValue(Class<?> type) {
050            try {
051                return Arrays.asList(getServiceImpls(type));
052            } catch (NoClassDefFoundError e) {
053                if (SuppressNoClassDefFoundError) {
054                    return Collections.emptyList();
055                } else {
056                    NoClassDefFoundError newEx = new NoClassDefFoundError(e.getMessage() + "  (suppress with -D" + SUPPRESS_PROPERTY_NAME + "=true)");
057                    if (e.getCause() != null) {
058                        newEx.initCause(e.getCause());
059                    }
060                    throw newEx;
061                }
062            }
063        }
064    };
065
066    /**
067     * Gets an {@link Iterable} of the JVMCI providers available for a given service.
068     *
069     * @throws SecurityException if a security manager is present and it denies
070     *             <tt>{@link RuntimePermission}("jvmciServices")</tt>
071     */
072    @SuppressWarnings("unchecked")
073    @CallerSensitive
074    public static <S> Iterable<S> load(Class<S> service) {
075        SecurityManager sm = System.getSecurityManager();
076        if (sm != null) {
077            sm.checkPermission(new RuntimePermission("jvmciServices"));
078        }
079        try {
080            return (Iterable<S>) cache.get(service);
081        } catch (UnsatisfiedLinkError e) {
082            return Collections.emptyList();
083        }
084    }
085
086    /**
087     * Gets the JVMCI provider for a given service for which at most one provider must be available.
088     *
089     * @param service the service whose provider is being requested
090     * @param required specifies if an {@link InternalError} should be thrown if no provider of
091     *            {@code service} is available
092     * @throws SecurityException if a security manager is present and it denies
093     *             <tt>{@link RuntimePermission}("jvmciServices")</tt>
094     */
095    @SuppressWarnings({"unchecked"})
096    @CallerSensitive
097    public static <S> S loadSingle(Class<S> service, boolean required) {
098        SecurityManager sm = System.getSecurityManager();
099        if (sm != null) {
100            sm.checkPermission(new RuntimePermission("jvmciServices"));
101        }
102        Iterable<S> providers;
103        try {
104            providers = (Iterable<S>) cache.get(service);
105        } catch (UnsatisfiedLinkError e) {
106            providers = Collections.emptyList();
107        }
108
109        S singleProvider = null;
110        for (S provider : providers) {
111            if (singleProvider != null) {
112                throw new InternalError(String.format("Multiple %s providers found: %s, %s", service.getName(), singleProvider.getClass().getName(), provider.getClass().getName()));
113            }
114            singleProvider = provider;
115        }
116        if (singleProvider == null && required) {
117            String javaHome = System.getProperty("java.home");
118            String vmName = System.getProperty("java.vm.name");
119            Formatter errorMessage = new Formatter();
120            errorMessage.format("The VM does not expose required service %s.%n", service.getName());
121            errorMessage.format("Currently used Java home directory is %s.%n", javaHome);
122            errorMessage.format("Currently used VM configuration is: %s", vmName);
123            throw new UnsupportedOperationException(errorMessage.toString());
124        }
125        return singleProvider;
126    }
127
128    static {
129        Reflection.registerMethodsToFilter(Services.class, "getServiceImpls");
130        Reflection.registerFieldsToFilter(Services.class, "cache");
131    }
132
133    private static native <S> S[] getServiceImpls(Class<?> service);
134}