1 package org.apache.commons.digester3.plugins; 2 3 /* 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, 15 * software distributed under the License is distributed on an 16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 17 * KIND, either express or implied. See the License for the 18 * specific language governing permissions and limitations 19 * under the License. 20 */ 21 22 import org.apache.commons.digester3.Digester; 23 import org.apache.commons.logging.Log; 24 25 /** 26 * Simple utility class to assist in logging. 27 * <p> 28 * This class is intended only for the use of the code in the plugins packages. No "user" code should use this package. 29 * <p> 30 * The Digester module has an interesting approach to logging: all logging should be done via the Log object stored on 31 * the digester instance that the object *doing* the logging is associated with. 32 * <p> 33 * This is done because apparently some "container"-type applications such as Avalon and Tomcat need to be able to 34 * configure different logging for different <i>instances</i> of the Digester class which have been loaded from the same 35 * ClassLoader [info from Craig McClanahan]. Not only the logging of the Digester instance should be affected; all 36 * objects associated with that Digester instance should obey the reconfiguration of their owning Digester instance's 37 * logging. The current solution is to force all objects to output logging info via a single Log object stored on the 38 * Digester instance they are associated with. 39 * <p> 40 * Of course this causes problems if logging is attempted before an object <i>has</i> a valid reference to its owning 41 * Digester. The getLogging method provided here resolves this issue by returning a Log object which silently discards 42 * all logging output in this situation. 43 * <p> 44 * And it also implies that logging filtering can no longer be applied to subcomponents of the Digester, because all 45 * logging is done via a single Log object (a single Category). C'est la vie... 46 * 47 * @since 1.6 48 */ 49 class LogUtils 50 { 51 52 /** 53 * Get the Log object associated with the specified Digester instance, or a "no-op" logging object if the digester 54 * reference is null. 55 * <p> 56 * You should use this method instead of digester.getLogger() in any situation where the digester might be null. 57 */ 58 static Log getLogger( Digester digester ) 59 { 60 if ( digester == null ) 61 { 62 return new org.apache.commons.logging.impl.NoOpLog(); 63 } 64 65 return digester.getLogger(); 66 } 67 68 }