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 * Copyright (c) 2015, 2021, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package jdk.internal.logger;

import jdk.internal.misc.VM;

import java.lang.ref.Reference;

import java.lang.ref.WeakReference;

import java.util.HashMap;

import java.util.Map;

import java.util.function.Function;

import java.util.Objects;

import java.lang.System.LoggerFinder;

import java.lang.System.Logger;

import java.lang.ref.ReferenceQueue;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.Collection;

import java.util.ResourceBundle;

/**

 * Internal Service Provider Interface (SPI) that makes it possible to use

 * {@code java.util.logging} as backend when the {@link

 * sun.util.logging.internal.LoggingProviderImpl

 * sun.util.logging.internal.LoggingProviderImpl} is present.

 * <p>

 * The JDK default implementation of the {@link LoggerFinder} will

 * attempt to locate and load an {@linkplain

 * java.util.ServiceLoader#loadInstalled(java.lang.Class) installed}

 * implementation of the {@code DefaultLoggerFinder}. If {@code java.util.logging}

 * is present, this will usually resolve to an instance of {@link

 * sun.util.logging.internal.LoggingProviderImpl sun.util.logging.internal.LoggingProviderImpl}.

 * Otherwise, if no concrete service provider is declared for

 * {@code DefaultLoggerFinder}, the default implementation provided by this class

 * will be used.

 * <p>

 * When the {@link sun.util.logging.internal.LoggingProviderImpl

 * sun.util.logging.internal.LoggingProviderImpl} is not present then the

 * default implementation provided by this class is to use a simple logger

 * that will log messages whose level is INFO and above to the console.

 * These simple loggers are not configurable.

 * <p>

 * When configuration is needed, an application should either link with

 * {@code java.util.logging} - and use the {@code java.util.logging} for

 * configuration, or link with {@link LoggerFinder another implementation}

 * of the {@link LoggerFinder}

 * that provides the necessary configuration.

 *

 * @apiNote Programmers are not expected to call this class directly.

 * Instead they should rely on the static methods defined by {@link

 * java.lang.System java.lang.System} or {@link sun.util.logging.PlatformLogger

 * sun.util.logging.PlatformLogger}.

 *

 * @see java.lang.System.LoggerFinder

 * @see jdk.internal.logger

 * @see sun.util.logging.internal

 *

 */

public class DefaultLoggerFinder extends LoggerFinder {

    static final RuntimePermission LOGGERFINDER_PERMISSION =

                new RuntimePermission("loggerFinder");

    /**

     * Creates a new instance of DefaultLoggerFinder.

     * @throws SecurityException if the calling code does not have the

     * {@code RuntimePermission("loggerFinder")}

     */

    protected DefaultLoggerFinder() {

        this(checkPermission());

    }

    private DefaultLoggerFinder(Void unused) {

        // nothing to do.

    }

    private static Void checkPermission() {

        @SuppressWarnings("removal")

        final SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            sm.checkPermission(LOGGERFINDER_PERMISSION);

        }

        return null;

    }

    // SharedLoggers is a default cache of loggers used when JUL is not

    // present - in that case we use instances of SimpleConsoleLogger which

    // cannot be directly configure through public APIs.

    //

    // We can therefore afford to simply maintain two domains - one for the

    // system, and one for the application.

    //

    static final class SharedLoggers {

        private final Map<String, Reference<Logger>> loggers =

                new HashMap<>();

        private final ReferenceQueue<Logger> queue = new ReferenceQueue<>();

        synchronized Logger get(Function<String, Logger> loggerSupplier, final String name) {

            Reference<? extends Logger> ref = loggers.get(name);

            Logger w = ref == null ? null :  ref.get();

            if (w == null) {

                w = loggerSupplier.apply(name);

                loggers.put(name, new WeakReference<>(w, queue));

            }

            // Remove stale mapping...

            Collection<Reference<Logger>> values = null;

            while ((ref = queue.poll()) != null) {

                if (values == null) values = loggers.values();

                values.remove(ref);

            }

            return w;

        }

        static final SharedLoggers system = new SharedLoggers();

        static final SharedLoggers application = new SharedLoggers();

    }

    @SuppressWarnings("removal")

    public static boolean isSystem(Module m) {

        return AccessController.doPrivileged(new PrivilegedAction<>() {

            @Override

            public Boolean run() {

                // returns true if moduleCL is the platform class loader

                // or one of its ancestors.

                return VM.isSystemDomainLoader(m.getClassLoader());

            }

        });

    }

    @Override

    public final Logger getLogger(String name,  Module module) {

        Objects.requireNonNull(name, "name");

        Objects.requireNonNull(module, "module");

        checkPermission();

        return demandLoggerFor(name, module);

    }

    @Override

    public final Logger getLocalizedLogger(String name, ResourceBundle bundle,

                                           Module module) {

        return super.getLocalizedLogger(name, bundle, module);

    }

    /**

     * Returns a {@link Logger logger} suitable for use within the

     * given {@code module}.

     *

     * @implSpec The default implementation for this method is to return a

     *    simple logger that will print all messages of INFO level and above

     *    to the console. That simple logger is not configurable.

     *

     * @param name The name of the logger.

     * @param module The module on behalf of which the logger is created.

     * @return A {@link Logger logger} suitable for the application usage.

     * @throws SecurityException if the calling code does not have the

     * {@code RuntimePermission("loggerFinder")}.

     */

    protected Logger demandLoggerFor(String name, Module module) {

        checkPermission();

        if (isSystem(module)) {

            return SharedLoggers.system.get(SimpleConsoleLogger::makeSimpleLogger, name);

        } else {

            return SharedLoggers.application.get(SimpleConsoleLogger::makeSimpleLogger, name);

        }

    }

}