http://commons.apache.org/digester/: The Apache Commons Digester package lets you configure an XML to Java object mapping module which triggers certain actions called rules whenever a particular pattern of nested XML elements is recognized. (The Apache Software Foundation)
  • Bradley M. Handy
  • Christopher Lenz
  • Ted Husted
  • David H. Martin
  • Henri Chen
  • Janek Bogucki
  • Mark Huisman
  • Paul Jack
  • Anton Maslovsky
  • Matt Cleveland
  • Gabriele Carcassi
  • Wendy Smoak
  • Kevin Ross
  • Daniele Testa
  • Craig McClanahan
  • Robert Burrell Donkin
  • Scott Sanders
  • James Strachan
  • Jason van Zyl
  • Tim OBrien
  • Jean-Francois Arcand
  • Simon Kitching
  • Rahul Akolkar
  • Simone Tripodi
  • Matt Benson 
package org.apache.commons.digester3.plugins;

/*
 * 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.
 */

import org.apache.commons.digester3.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();
    }

}