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There is a newer version: 3.9.0
/*
 * Copyright (c) MuleSoft, Inc.  All rights reserved.  http://www.mulesoft.com
 * The software in this package is published under the terms of the CPAL v1.0
 * license, a copy of which has been included with this distribution in the
 * LICENSE.txt file.
 */
package org.mule.util;

import org.slf4j.Logger;

/**
 * Utility class to log a warning message only once during the lifecycle of a component.
 * The {@link #warn()} message will log that message only once, in a thread-safe manner.
 * This component is conceived with the intent of allowing deprecated components to warn
 * that they should not be used anymore.
 *
 * @since 3.6.0
 */
public class OneTimeWarning
{

    private final Logger logger;
    private final String message;
    private boolean warned = false;
    private Delegate delegate = new FirstTimeDelegate();

    public OneTimeWarning(Logger logger, String message)
    {
        this.logger = logger;
        this.message = message;
    }

    /**
     * Fire one time warning.
     */
    public void warn()
    {
        delegate.warn();
    }

    /**
     * Fire one time warning using arguments passing arguments to logger
     *
     * @param args arguments to pass to logger along with message defined when this instance was created.
     */
    public void warn(Object... args)
    {
        delegate.warn(args);
    }

    private interface Delegate
    {

        void warn();

        void warn(Object... args);
    }

    private class FirstTimeDelegate implements Delegate
    {

        @Override
        public synchronized void warn()
        {
            warn(null);
        }

        @Override
        public synchronized void warn(Object... args)
        {
            if (warned == false)
            {
                if (args != null)
                {
                    logger.warn(message, args);
                }
                else
                {
                    logger.warn(message);
                }
                warned = true;
                delegate = new NoOpDelegate();
            }
        }
    }

    private class NoOpDelegate implements Delegate
    {

        @Override
        public void warn()
        {
        }

        @Override
        public void warn(Object... args)
        {
        }
    }
}