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/*
 * Copyright 2012 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.util.internal.logging;

import io.netty.util.internal.ObjectUtil;

/**
 * Creates an {@link InternalLogger} or changes the default factory
 * implementation.  This factory allows you to choose what logging framework
 * Netty should use.  The default factory is {@link Slf4JLoggerFactory}.  If SLF4J
 * is not available, {@link Log4JLoggerFactory} is used.  If Log4J is not available,
 * {@link JdkLoggerFactory} is used.  You can change it to your preferred
 * logging framework before other Netty classes are loaded:
 *  * {@link InternalLoggerFactory}.setDefaultFactory({@link Log4JLoggerFactory}.INSTANCE);
 * 
 * Please note that the new default factory is effective only for the classes
 * which were loaded after the default factory is changed.  Therefore,
 * {@link #setDefaultFactory(InternalLoggerFactory)} should be called as early
 * as possible and shouldn't be called more than once.
 */
public abstract class InternalLoggerFactory {

    private static volatile InternalLoggerFactory defaultFactory;

    @SuppressWarnings("UnusedCatchParameter")
    private static InternalLoggerFactory newDefaultFactory(String name) {
        InternalLoggerFactory f = useSlf4JLoggerFactory(name);
        if (f != null) {
            return f;
        }

        f = useLog4J2LoggerFactory(name);
        if (f != null) {
            return f;
        }

        f = useLog4JLoggerFactory(name);
        if (f != null) {
            return f;
        }

        return useJdkLoggerFactory(name);
    }

    private static InternalLoggerFactory useSlf4JLoggerFactory(String name) {
        try {
            InternalLoggerFactory f = Slf4JLoggerFactory.getInstanceWithNopCheck();
            f.newInstance(name).debug("Using SLF4J as the default logging framework");
            return f;
        } catch (LinkageError ignore) {
            return null;
        } catch (Exception ignore) {
            // We catch Exception and not ReflectiveOperationException as we still support java 6
            return null;
        }
    }

    private static InternalLoggerFactory useLog4J2LoggerFactory(String name) {
        try {
            InternalLoggerFactory f = Log4J2LoggerFactory.INSTANCE;
            f.newInstance(name).debug("Using Log4J2 as the default logging framework");
            return f;
        } catch (LinkageError ignore) {
            return null;
        } catch (Exception ignore) {
            // We catch Exception and not ReflectiveOperationException as we still support java 6
            return null;
        }
    }

    private static InternalLoggerFactory useLog4JLoggerFactory(String name) {
        try {
            InternalLoggerFactory f = Log4JLoggerFactory.INSTANCE;
            f.newInstance(name).debug("Using Log4J as the default logging framework");
            return f;
        } catch (LinkageError ignore) {
            return null;
        } catch (Exception ignore) {
            // We catch Exception and not ReflectiveOperationException as we still support java 6
            return null;
        }
    }

    private static InternalLoggerFactory useJdkLoggerFactory(String name) {
        InternalLoggerFactory f = JdkLoggerFactory.INSTANCE;
        f.newInstance(name).debug("Using java.util.logging as the default logging framework");
        return f;
    }

    /**
     * Returns the default factory.  The initial default factory is
     * {@link JdkLoggerFactory}.
     */
    public static InternalLoggerFactory getDefaultFactory() {
        if (defaultFactory == null) {
            defaultFactory = newDefaultFactory(InternalLoggerFactory.class.getName());
        }
        return defaultFactory;
    }

    /**
     * Changes the default factory.
     */
    public static void setDefaultFactory(InternalLoggerFactory defaultFactory) {
        InternalLoggerFactory.defaultFactory = ObjectUtil.checkNotNull(defaultFactory, "defaultFactory");
    }

    /**
     * Creates a new logger instance with the name of the specified class.
     */
    public static InternalLogger getInstance(Class clazz) {
        return getInstance(clazz.getName());
    }

    /**
     * Creates a new logger instance with the specified name.
     */
    public static InternalLogger getInstance(String name) {
        return getDefaultFactory().newInstance(name);
    }

    /**
     * Creates a new logger instance with the specified name.
     */
    protected abstract InternalLogger newInstance(String name);

}