devbox@COMPUTEC The Computec development blog

ColdFusion UDF to test if a Java Class implements a method

I recently started implementing a couple of our full text search requirements using Sphinx. I am extremely happy with this search engine, as it's lightning fast and provides some quite easy integration with the data we store in our PostgreSQL databases, is highly scalable and fairly easy to implement in ColdFusion via the Sphinx Client API. 

As I started writing the search component for our articles, I decided that it would be an extremely valuable feature to use the weighting functionality Sphinx provides. This would allow to set different weights to the indexed fields on a per-query basis, which is extremely cool as you don't have to decide on a general per-field weighting setting during indexing.

The Sphinx API documentation does mention a SetFieldWeights-method which takes a HashMap (i.e. an associative array for those of the PHP persuasion) as argument. I constructed the Hashmap like this (excerpt from a function):

var jHashMap = createobject("java", "java.util.HashMap");
jHashMap.put('keywords',JavaCast('int',arguments.iWeightType));
jHashMap.put('text',JavaCast('int',arguments.iWeightText));

So far, so good. Now I tried calling

variables.sphinx.SetFieldWeights(jHashMap);

- and received an error that this function does not exist. One dump of the Sphinx-API later, I saw the error was a mere typo: In org.sphx.api.SphinxClient the method was actually spelled SetFieldeights. Being a responsible user, I did report this bug in the forums, but what to do for the time being? Two options: Correct the spelling mistake in the API-source, recompile and redeploy - and risk that a subsequent update might have to be patched as well (and one tends to forget something like that) or just accept the typo in my own code. I sort of opted for the latter, but I wanted to be equally safe from a later correction of this typo in an updated API.

So I wanted to make my code work with both SetFieldeights or SetFieldWeights. This could be done either by CFTRY/CFCATCHING an error on calling the method (something I try to avoid at all costs), or simply checking if the method is implemented by the class.

Now my first try with structKeyExists() failed. Apparently I cannot test a java object as if it were a structure, or probably more like I cannot test a method of such an object as if it were a member of a conventional structure. isDefined() failed, probably for similar reasons. Okay, on to the good Java stuff. Java provides reflection for such cases, in fact this is what ColdFusion uses when you cfdump such an object.

To make this reusable, decided to write this as as more generic function I could use in another CFC:

<cffunction name="methodExists" returntype="boolean" access="public" output="no" hint="checks if a java class implements a method">
	<cfargument name="strClassName" type="string" required="yes">
	<cfargument name="strMethodName" type="string" required="yes">
	<cfscript>
		var a = arrayNew(1);
		var myClass = a.getClass().forName(arguments.strClassName);
		var arrMethods = myClass.getDeclaredMethods();
		var i = 1;
		var arrMethodNames = arrayNew(1);
		for (i=1; i lte ArrayLen(arrMethods); i++) {
			arrMethodNames[i] = arrMethods[i].getName();
		}
		if (arrMethodNames.indexOf(arguments.strMethodName) eq -1) {
			return false;
			} else {
			return true;
		}			
	</cfscript>
</cffunction>

Now to check if the Sphinx-API implements SetFieldWeights, I just need to test the boolean return value like

<cfscript>
if (methodExists(strClassName='org.sphx.api.SphinxClient',strMethodName='SetFieldWeights')) {
  variables.sphinx.SetFieldWeights(jHashMap);
  } else {
  variables.sphinx.SetFieldeights(jHashMap);
}
</cfscript>

Mission accomplished! For those curious to know, the affected Sphinx version was sphinx-0.9.9-rc2.