/* $Id: LogUtils.java 992060 2010-09-02 19:09:47Z simonetripodi $
 *
 * 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/**
 * Simple utility class to assist in logging.
 * <p>
 * This class is intended only for the use of the code in the
 * plugins packages. No "user" code should use this package.
 * <p>
 * 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.
 * <p>
 * This is done because apparently some "container"-type applications
 * such as Avalon and Tomcat need to be able to configure different logging
 * for different <i>instances</i> 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.
 * <p>
 * Of course this causes problems if logging is attempted before an
 * object <i>has</i> 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.
 * <p>
 * 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.
/**
   * Get the Log object associated with the specified Digester instance,
   * or a "no-op" logging object if the digester reference is null.
   * <p>
   * 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();
  }
}