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Date: 25 Nov 2004 20:09:53 -0000
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From: rdonkin@apache.org
To: jakarta-commons-cvs@apache.org
Subject: cvs commit:
 jakarta-commons/logging/optional/src/java/org/apache/commons/logging/impl
 WeakHashtable.java
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rdonkin     2004/11/25 12:09:53

  Modified:    logging/optional/src/java/org/apache/commons/logging/impl
                        WeakHashtable.java
  Log:
  Class level documentation. Contributed by Brian Stansberry
  
  Revision  Changes    Path
  1.5       +27 -2     jakarta-commons/logging/optional/src/java/org/apache/commons/logging/impl/WeakHashtable.java
  
  Index: WeakHashtable.java
  ===================================================================
  RCS file: /home/cvs/jakarta-commons/logging/optional/src/java/org/apache/commons/logging/impl/WeakHashtable.java,v
  retrieving revision 1.4
  retrieving revision 1.5
  diff -u -r1.4 -r1.5
  --- WeakHashtable.java	17 Nov 2004 23:23:21 -0000	1.4
  +++ WeakHashtable.java	25 Nov 2004 20:09:53 -0000	1.5
  @@ -35,9 +35,34 @@
    * <p>
    * <strong>Usage:</strong> typical use case is as a drop-in replacement 
    * for the <code>Hashtable</code> use in <code>LogFactory</code> for J2EE enviroments
  - * running 1.3+ JVMs. Use of this class will allow classloaders to be collected by 
  - * the garbage collector without the need to call release.
  + * running 1.3+ JVMs. Use of this class <i>in most cases</i> (see below) will
  + * allow classloaders to be collected by the garbage collector without the need 
  + * to call {@link org.apache.commons.logging.LogFactory#release(ClassLoader) LogFactory.release(ClassLoader)}.
    * </p>
  + * <p>
  + * In a particular usage scenario, use of <code>WeakHashtable</code> alone will
  + * be insufficent to allow garbage collection of a classloader without a call to
  + * <code>release</code>.  If the abstract class <code>LogFactory</code> is 
  + * loaded by a parent classloader and a concrete subclass implementation of 
  + * <code>LogFactory</code> is loaded by a child classloader, the concrete
  + * implementation will have a strong reference to the child classloader via the
  + * chain <code>getClass().getClassLoader()</code>. The <code>WeakHashtable</code>
  + * will have a strong reference to the <code>LogFactory</code> implementation as
  + * one of the values in its map. This chain of references will prevent 
  + * collection of the child classloader.
  + * </p>
  + * <p>
  + * Such a situation would typically only occur if commons-logging.jar were
  + * loaded by a parent classloader (e.g. a server level classloader in a
  + * servlet container) and a custom <code>LogFactory</code> implementation were
  + * loaded by a child classloader (e.g. a web app classloader).  If use of
  + * a custom <code>LogFactory</code> subclass is desired, ensuring that the
  + * custom subclass is loaded by the same classloader as <code>LogFactory</code>
  + * will prevent problems.  In normal deployments, the standard implementations 
  + * of <code>LogFactory</code> found in package <code>org.apache.commons.logging.impl</code> 
  + * will be loaded by the same classloader that loads <code>LogFactory</code> 
  + * itself, so use of the standard <code>LogFactory</code> implementations
  + * should not pose problems.
    * 
    * @author Brian Stansberry
    */
  
  
  

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