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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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/*
 * Copyright 2023 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.bootstrap;

import io.netty.util.internal.SystemPropertyUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.ServiceLoader;

/**
 * The configurable facade that decides what {@link ChannelInitializerExtension}s to load and where to find them.
 */
abstract class ChannelInitializerExtensions {
    private static final InternalLogger logger = InternalLoggerFactory.getInstance(ChannelInitializerExtensions.class);
    private static volatile ChannelInitializerExtensions implementation;

    private ChannelInitializerExtensions() {
    }

    /**
     * Get the configuration extensions, which is a no-op implementation by default,
     * or a service-loading implementation if the {@code io.netty.bootstrap.extensions} system property is
     * {@code serviceload}.
     */
    static ChannelInitializerExtensions getExtensions() {
        ChannelInitializerExtensions impl = implementation;
        if (impl == null) {
            synchronized (ChannelInitializerExtensions.class) {
                impl = implementation;
                if (impl != null) {
                    return impl;
                }
                String extensionProp = SystemPropertyUtil.get(ChannelInitializerExtension.EXTENSIONS_SYSTEM_PROPERTY);
                logger.debug("-Dio.netty.bootstrap.extensions: {}", extensionProp);
                if ("serviceload".equalsIgnoreCase(extensionProp)) {
                    impl = new ServiceLoadingExtensions(true);
                } else if ("log".equalsIgnoreCase(extensionProp)) {
                    impl = new ServiceLoadingExtensions(false);
                } else {
                    impl = new EmptyExtensions();
                }
                implementation = impl;
            }
        }
        return impl;
    }

    /**
     * Get the list of available extensions. The list is unmodifiable.
     */
    abstract Collection extensions(ClassLoader cl);

    private static final class EmptyExtensions extends ChannelInitializerExtensions {
        @Override
        Collection extensions(ClassLoader cl) {
            return Collections.emptyList();
        }
    }

    private static final class ServiceLoadingExtensions extends ChannelInitializerExtensions {
        private final boolean loadAndCache;

        private WeakReference classLoader;
        private Collection extensions;

        ServiceLoadingExtensions(boolean loadAndCache) {
            this.loadAndCache = loadAndCache;
        }

        @SuppressWarnings("AssignmentOrReturnOfFieldWithMutableType")
        @Override
        synchronized Collection extensions(ClassLoader cl) {
            ClassLoader configured = classLoader == null ? null : classLoader.get();
            if (configured == null || configured != cl) {
                Collection loaded = serviceLoadExtensions(loadAndCache, cl);
                classLoader = new WeakReference(cl);
                extensions = loadAndCache ? loaded : Collections.emptyList();
            }
            return extensions;
        }

        private static Collection serviceLoadExtensions(boolean load, ClassLoader cl) {
            List extensions = new ArrayList();

            ServiceLoader loader = ServiceLoader.load(
                    ChannelInitializerExtension.class, cl);
            for (ChannelInitializerExtension extension : loader) {
                extensions.add(extension);
            }

            if (!extensions.isEmpty()) {
                Collections.sort(extensions, new Comparator() {
                    @Override
                    public int compare(ChannelInitializerExtension a, ChannelInitializerExtension b) {
                        return Double.compare(a.priority(), b.priority());
                    }
                });
                logger.info("ServiceLoader {}(s) {}: {}", ChannelInitializerExtension.class.getSimpleName(),
                        load ? "registered" : "detected", extensions);
                return Collections.unmodifiableList(extensions);
            }
            logger.debug("ServiceLoader {}(s) {}: []", ChannelInitializerExtension.class.getSimpleName(),
                    load ? "registered" : "detected");
            return Collections.emptyList();
        }
    }
}