Re: Class cache in JavaBaseFactory...

[Brian Lawler]

So at long last, here is the patch for JavaBaseFactory, for you perusal  
(again).  Just to refresh the context, the problem that we ran into on  
our site is that excessive calls to Class.forName() in the  
JavaBaseFactory was bubbling up to the top of our profiler output.   
Turns out that the Base Factory was repeatedly calling Class.forName  
for the same class name.  This is easily remedied by just creating a  
Map of Class instances in the JavaBaseFactory class.

Here is the patch, applied against TURBINE_2_3_BRANCH:
Index:  
src/java/org/apache/turbine/services/assemblerbroker/util/java/ 
JavaBaseFactory.java
===================================================================
RCS file:  
/home/cvspublic/jakarta-turbine-2/src/java/org/apache/turbine/services/ 
assemblerbroker/util/java/JavaBaseFactory.java,v
retrieving revision 1.8.2.2
diff -u -r1.8.2.2 JavaBaseFactory.java
---  
src/java/org/apache/turbine/services/assemblerbroker/util/java/ 
JavaBaseFactory.java 20 May 2004 03:05:16 -0000      1.8.2.2
+++  
src/java/org/apache/turbine/services/assemblerbroker/util/java/ 
JavaBaseFactory.java 7 Jul 2004 18:13:17 -0000
@@ -16,7 +16,10 @@
  * limitations under the License.
  */

+import java.util.Collections;
+import java.util.HashMap;
 import java.util.Iterator;
+import java.util.Map;
 import java.util.Vector;
 import org.apache.commons.lang.StringUtils;
@@ -35,9 +38,7 @@
  * A screen factory that attempts to load a java class from
  * the module packages defined in the TurbineResource.properties.
  *
- * @author <a href="mailto:[EMAIL PROTECTED]">Leon Messerschmidt</a>
- * @author <a href="mailto:[EMAIL PROTECTED]">Henning P.  
Schmiedehausen</a>
- * @version $Id: JavaBaseFactory.java,v 1.8.2.2 2004/05/20 03:05:16  
seade Exp $
+ * @version $Id: JavaBaseFactory.java,v 1.2 2004/07/07 17:45:05 brian  
Exp $
  */
 public abstract class JavaBaseFactory
     implements AssemblerFactory
@@ -49,6 +50,12 @@
     /** Logging */
     protected Log log = LogFactory.getLog(this.getClass());

+    /**
+     * A cache for previously obtained Class instances, which we keep  
in order
+     * to reduce the Class.forName() overhead (which can be sizable).
+     */
+    private Map classCache = Collections.synchronizedMap(new  
HashMap());
+
     static
     {
         ObjectUtils.addOnce(packages, GenericLoader.getBasePackage());
@@ -69,7 +76,7 @@

         if (StringUtils.isNotEmpty(name))
         {
-            for (Iterator it = packages.iterator(); it.hasNext();)
+            for (Iterator it = packages.iterator(); assembler == null  
&& it.hasNext();)
             {
                 StringBuffer className = new StringBuffer();

@@ -83,7 +90,12 @@
                 try
                 {
-                    Class servClass =  
Class.forName(className.toString());
+                    Class servClass = (Class)  
classCache.get(className);
+                    if(servClass == null)
+                    {
+                        servClass =  
Class.forName(className.toString());
+                        classCache.put(className, servClass);
+                    }
                     assembler = (Assembler) servClass.newInstance();
                     break; // for()
                 }

On Jun 12, 2004, at 1:37 AM, Brian Lawler wrote:
Henning-
On May 9, 2004, at 4:37 PM, Henning P. Schmiedehausen wrote:
You might either want to have some sort of real life cycle (which
would be overkill for a point release like 2.3.1) or, if just
Class.forName() is your bottleneck, simply store the Class objects and
not the instance objects. This could even be a class cache, not just
an instance cache, because translating
"com.mycorp.modules.actions.FooAction" to a Class object describing
the FooAction class is the same for all the instances.
Great point.  I have re-implemented this as a Class cache, since  
Class.forName() is indeed our bottleneck, and I will be testing it  
over the next few days.  I will send my patched patch when satisfied  
that it is doing the right thing...

-B
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