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 [EMAIL PROTECTED]
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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