org.refcodes.logger.ext.slf4j.RuntimeLoggerFactory Maven / Gradle / Ivy

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// /////////////////////////////////////////////////////////////////////////////
// REFCODES.ORG
// =============================================================================
// This code is copyright (c) by Siegfried Steiner, Munich, Germany, distributed
// on an "AS IS" BASIS WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, and licen-
// sed under the following (see "http://en.wikipedia.org/wiki/Multi-licensing")
// licenses:
// =============================================================================
// GNU General Public License, v3.0 ("http://www.gnu.org/licenses/gpl-3.0.html")
// together with the GPL linking exception applied; as being applied by the GNU
// Classpath ("http://www.gnu.org/software/classpath/license.html")
// =============================================================================
// Apache License, v2.0 ("http://www.apache.org/licenses/TEXT-2.0")
// =============================================================================
// Please contact the copyright holding author(s) of the software artifacts in
// question for licensing issues not being covered by the above listed licenses,
// also regarding commercial licensing models or regarding the compatibility
// with other open source licenses.
// /////////////////////////////////////////////////////////////////////////////
package org.refcodes.logger.ext.slf4j;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import org.refcodes.logger.RuntimeLogger;
import org.refcodes.logger.RuntimeLoggerFactorySingleton;
import org.slf4j.ILoggerFactory;
import org.slf4j.Logger;
import org.slf4j.bridge.SLF4JBridgeHandler;
import org.slf4j.helpers.NOPLogger;

/**
 * An {@link ILoggerFactory} factory for creating {@link RuntimeLogger} objects.
 */
public class RuntimeLoggerFactory implements ILoggerFactory {

	// /////////////////////////////////////////////////////////////////////////
	// VARIABLES:
	// /////////////////////////////////////////////////////////////////////////

	private final ConcurrentMap _nameToLoggerMap;

	private static final ThreadLocal _invocationCount = new ThreadLocal() {
		@Override
		protected Integer initialValue() {
			return 0;
		}
	};

	// /////////////////////////////////////////////////////////////////////////
	// CONSTRUCTORS:
	// /////////////////////////////////////////////////////////////////////////

	/**
	 * Instantiates a new runtime logger factory.
	 */
	public RuntimeLoggerFactory() {
		_nameToLoggerMap = new ConcurrentHashMap<>();
		SLF4JBridgeHandler.install();
	}

	// /////////////////////////////////////////////////////////////////////////
	// METHODS:
	// /////////////////////////////////////////////////////////////////////////

	/**
	 * {@inheritDoc}
	 */
	@Override
	public Logger getLogger( String name ) {
		/**
		 * An API involved in *creating* the logger wants to create a logger for
		 * itself as well while creating the desired logger. This causes an
		 * endless loop of logger creation invocations with the result of an
		 * StackOverflowError. To prevent this we count the number of
		 * invocations a thread has undertaken to determine whether we ended up
		 * in such a loop.
		 */
		if ( _invocationCount.get() != 0 ) {
			return NOPLogger.NOP_LOGGER;
		}
		_invocationCount.set( _invocationCount.get() + 1 );
		final Logger slf4jLogger = _nameToLoggerMap.get( name );
		if ( slf4jLogger != null ) {
			_invocationCount.remove();
			return slf4jLogger;
		}
		else {
			if ( name != null ) {
				name = name.replaceAll( "/", "." );
			}
			if ( name.length() > 0 && name.charAt( 0 ) == '.' ) {
				name = name.substring( 1 );
			}
			if ( name == null || name.isEmpty() ) {
				name = RuntimeLogger.ROOT_LOGGER_ELEMENT_PATH;
			}
			final RuntimeLogger theRuntimeLogger;
			if ( name.equalsIgnoreCase( Logger.ROOT_LOGGER_NAME ) ) {
				theRuntimeLogger = RuntimeLoggerFactorySingleton.createRuntimeLogger();
			}
			else {
				theRuntimeLogger = RuntimeLoggerFactorySingleton.getInstance().create( name );
			}
			final Logger newInstance = new RuntimeLoggerAdapter( theRuntimeLogger );
			final Logger oldInstance = _nameToLoggerMap.putIfAbsent( name, newInstance );
			_invocationCount.remove();
			return oldInstance == null ? newInstance : oldInstance;
		}
	}
}