Class cache in JavaBaseFactory...

[Brian Lawler]

Hey guys-

We were profiling our turbine application the other day and one thing  
that bubbled up to the top was the JavaBaseFactory.getAssembler()  
class.  This class iterates over all of the packages where Assemblers  
may be found and retrieves a Class instance when it encounters a hit.   
But it does this for every call to the getAssembler method, and we  
found the resulting time spent in Class.forName() to be very high.  I  
have placed a simple synchronized map in our version of the class that  
is used to cache previously found Assemblers and is queried before  
going through the package loop.  This lowered the time we spend in  
Class.forName() substantially.

First of all, is this not a good thing to do?

And second, if this *is* a good thing to do, here is the patch if you  
are interested...



Index:  
src/java/org/apache/turbine/services/assemblerbroker/util/java/ 
JavaBaseFactory.java
===================================================================
RCS file:  
/home/cvsroot/turbine/src/java/org/apache/turbine/services/ 
assemblerbroker/util/java/JavaBaseFactory.java,v
retrieving revision 1.1.1.2
diff -u -r1.1.1.2 JavaBaseFactory.java
---  
src/java/org/apache/turbine/services/assemblerbroker/util/java/ 
JavaBaseFactory.java 20 Apr 2004 23:59:23 -0000      1.1.1.2
+++  
src/java/org/apache/turbine/services/assemblerbroker/util/java/ 
JavaBaseFactory.java 21 Apr 2004 00:06:03 -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;
@@ -47,6 +50,9 @@
     /** Logging */
     protected Log log = LogFactory.getLog(this.getClass());
+    /** A cache for previously obtained assemblers */
+    private Map assemblerCache = Collections.synchronizedMap(new  
HashMap());
+
     static
     {
         ObjectUtils.addOnce(packages, GenericLoader.getBasePackage());
@@ -67,7 +73,8 @@

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

@@ -83,6 +90,7 @@
                 {
                     Class servClass =  
Class.forName(className.toString());
                     assembler = (Assembler) servClass.newInstance();
+                    assemblerCache.put(name, assembler);
                     break; // for()
                 }
                 catch (ClassNotFoundException cnfe)

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