cvs commit: jakarta-commons/digester/src/java/org/apache/commons/digester/plugins LogUtils.java

[rd...@apache.org]

rdonkin     2003/10/28 15:31:38

  Added:       digester/src/java/org/apache/commons/digester/plugins
                        LogUtils.java
  Log:
  Improvements to bring logging in line with the practice in the rest of digester.  Submitted by Simon Kitching.
  
  Revision  Changes    Path
  1.1                  jakarta-commons/digester/src/java/org/apache/commons/digester/plugins/LogUtils.java
  
  Index: LogUtils.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/digester/src/java/org/apache/commons/digester/plugins/LogUtils.java,v 1.1 2003/10/28 23:31:38 rdonkin Exp $
   * $Revision: 1.1 $
   * $Date: 2003/10/28 23:31:38 $
   *
   * ====================================================================
   * 
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
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  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.
   * <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...
   * 
   * @author Simon Kitching
   */
  
  public class LogUtils {
      
    /**
     * 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.
     */
    public static Log getLogger(Digester digester) {
      if (digester == null) {
          return new org.apache.commons.logging.impl.NoOpLog();
      }
      
      return digester.getLogger();
    }
  }
  
  
  

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