LogWriter.java

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 * OW2 Chameleon - Fuchsia Framework
 * %%
 * Copyright (C) 2009 - 2014 OW2 Chameleon
 * %%
 * Licensed 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
 * 
 *      http://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,
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/*
    Calimero - A library for KNX network access
    Copyright (C) 2006-2008 B. Malinowsky

    This program is free software; you can redistribute it and/or 
    modify it under the terms of the GNU General Public License 
    as published by the Free Software Foundation; either version 2 
    of the License, or at your option any later version. 
 
    This program 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 for more details. 
 
    You should have received a copy of the GNU General Public License 
    along with this program; if not, write to the Free Software 
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA. 
 
    Linking this library statically or dynamically with other modules is 
    making a combined work based on this library. Thus, the terms and 
    conditions of the GNU General Public License cover the whole 
    combination. 
 
    As a special exception, the copyright holders of this library give you 
    permission to link this library with independent modules to produce an 
    executable, regardless of the license terms of these independent 
    modules, and to copy and distribute the resulting executable under terms 
    of your choice, provided that you also meet, for each linked independent 
    module, the terms and conditions of the license of that module. An 
    independent module is a module which is not derived from or based on 
    this library. If you modify this library, you may extend this exception 
    to your version of the library, but you are not obligated to do so. If 
    you do not wish to do so, delete this exception statement from your 
    version. 
*/

package tuwien.auto.calimero.log;

/**
 * LogWriter is responsible for writing information to individual destinations.
 * <p>
 * A LogWriter has an assigned log level (by default {@link LogLevel#ALL}), which
 * specifies what information to write and what to ignore. A log level of
 * {@link LogLevel#OFF} will ignore any write requests. If a LogWriter is not used
 * anymore, {@link #close()} has to be called.
 * 
 * @author B. Malinowsky
 * @see LogLevel
 * @see LogService
 */
public abstract class LogWriter
{
	private static ErrorHandler errorHandler = new ErrorHandler();

	LogLevel logLevel = LogLevel.ALL;

	/**
	 * Sets the error handler used on all log writer errors.
	 * <p>
	 * 
	 * @param handler the new error handler
	 */
	public static synchronized void setErrorHandler(ErrorHandler handler)
	{
		if (handler != null)
			errorHandler = handler;
	}

	/**
	 * Returns the used error handler.
	 * <p>
	 * 
	 * @return an {@link ErrorHandler} object
	 */
	public static synchronized ErrorHandler getErrorHandler()
	{
		return errorHandler;
	}

	/**
	 * Sets the log level for deciding which messages gets logged by this LogWriter.
	 * <p>
	 * 
	 * @param level new log level
	 */
	public final void setLogLevel(LogLevel level)
	{
		logLevel = level;
	}

	/**
	 * Returns the log level used for deciding which messages will be logged.
	 * <p>
	 * 
	 * @return log {@link LogLevel}
	 */
	public final LogLevel getLogLevel()
	{
		return logLevel;
	}

	/**
	 * Writes a message out to this LogWriter.
	 * <p>
	 * The message has the associated log level <code>level</code>. It will only be
	 * written if the LogWriter logging level is not more restrictive than
	 * <code>level</code>. Otherwise the message is ignored. LogWriter is responsible
	 * for formatting the output.
	 * 
	 * @param logService log service name stating the source of the message
	 * @param level log level of message
	 * @param msg the message to write
	 */
	public abstract void write(String logService, LogLevel level, String msg);

	/**
	 * Like {@link #write(String, LogLevel, String)}, in addition a
	 * <code>Throwable</code> object is taken which will be added to the message.
	 * 
	 * @param logService log service name stating the source of the message
	 * @param level log level of message
	 * @param msg the message to write
	 * @param t Throwable object, might be <code>null</code>
	 */
	public abstract void write(String logService, LogLevel level, String msg, Throwable t);

	/**
	 * Flushes all buffered output.
	 */
	public abstract void flush();

	/**
	 * Closes the LogWriter and all its resources.
	 * <p>
	 * If necessary, all output is flushes before.
	 */
	public abstract void close();
}