org.apache.commons.digester.plugins.LogUtils Maven / Gradle / Ivy
/* $Id: LogUtils.java 471661 2006-11-06 08:09:25Z skitching $
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF 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
*
* 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,
* 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 org.apache.commons.digester.plugins;
import org.apache.commons.digester.Digester;
import org.apache.commons.logging.Log;
/**
* Simple utility class to assist in logging.
*
* This class is intended only for the use of the code in the
* plugins packages. No "user" code should use this package.
*
* The Digester module has an interesting approach to logging:
* all logging should be done via the Log object stored on the
* digester instance that the object *doing* the logging is associated
* with.
*
* This is done because apparently some "container"-type applications
* such as Avalon and Tomcat need to be able to configure different logging
* for different instances of the Digester class which have been
* loaded from the same ClassLoader [info from Craig McClanahan].
* Not only the logging of the Digester instance should be affected; all
* objects associated with that Digester instance should obey the
* reconfiguration of their owning Digester instance's logging. The current
* solution is to force all objects to output logging info via a single
* Log object stored on the Digester instance they are associated with.
*
* Of course this causes problems if logging is attempted before an
* object has a valid reference to its owning Digester. The
* getLogging method provided here resolves this issue by returning a
* Log object which silently discards all logging output in this
* situation.
*
* And it also implies that logging filtering can no longer be applied
* to subcomponents of the Digester, because all logging is done via
* a single Log object (a single Category). C'est la vie...
*
* @since 1.6
*/
class LogUtils {
/**
* Get the Log object associated with the specified Digester instance,
* or a "no-op" logging object if the digester reference is null.
*
* You should use this method instead of digester.getLogger() in
* any situation where the digester might be null.
*/
static Log getLogger(Digester digester) {
if (digester == null) {
return new org.apache.commons.logging.impl.NoOpLog();
}
return digester.getLogger();
}
}