How ColdFusion CreateObject() Really Works With Java Objects

Thathow I understood it to be after Rupesh's and Sean's comments.

You can search "Cold" word in http://searchcode.tm-sol.com/. might give you some examples also.

found good examples as well.

How do you free the memory used by this object on the coldfusion server?

you can also create WebService objects this way.

i.e.:
<cfscript>
dynamicsWS = CreateObject("webservice", "http://192.168.0.100/DynamicsGPWebServices/DynamicsGPService.asmx?WSDL");
</cfscript>

<cfinvoke webservice="#dynamicsWS#" method="GetCompanyList" refreshWSDL="yes" timeout="30" returnvariable="result">
</cfinvoke>

This creates WebService object in your ColdFusion instance (available from administration panel -> webservices) and this object "lives" in there for about 10 (gets deleted if not used).

So I never took CreateObject() for granted :)

Ben, sheds some light on the subject for me. I've recently ventured into a shared hosting enviroment to do some outside work, and quickly ran into the java object disabled issue.

I'm not much of a programer, more a manager and integrator and struggling to find a workaround for some open source I'm using.

Thanks for the overview.

One quick point: I'm less certain that "object instantiation is a costly process" - object instantiation is strongly optimized on the JVM, and even reflection has far less cost than before.

IMO, the reason for the init pattern is to allow access to statics with less hoops; though this creates a somewhat schizophrenic API.

Nitpicks aside, thanks for another clear and lucid explanation of one of the details of the CF platform. Your blog has been extremely helpful to me as I learn!

I know this is a bit of an old thread, but I recently discovered something relevant. The init() function call on CF proxy objects is not thread safe.

Recently we began having random documents inserted into the incorrect collection on our MongoDB. We tracked it down to our own Mongo driver which leverages the Mongo Java driver as a singleton. However, in concurrency situations, creating new instances of our java class using the above method caused us sometimes to get the wrong instance back.

For example:
Process A calls init("collection1")
Process B calls init("collection2")
Both calls return CF proxy objects with the same instance of our CFMongo class pointing to collection2.

So if you are going to cache your static class in a shared location, like the application scope, you need to only call init() with an exclusion lock. In our case we chose to use CreateObject() each time passing the mongo driver singleton into the constructor.

Hi Ben, interesting post.

It looks like I'm running into the CF proxy object as an issue on a routine I'm writing.

I'm importing the Amazon Web Services SDK for Java into a CFC and to initialise the S3 Client you first have to create an authentication object. However passing this object (which is created correctly) to the init() function throws an "An exception occurred while instantiating a Java object. The class must not be an interface or an abstract class" error.

I'm guessing that because this isn't a true Java object the second class doesn't like it?

Anyway here's the code:

awsCred = createobject('java',
		'com.amazonaws.auth.BasicAWSCredentials').init(
		accessKey,
		secretKey
		);
// this works fine; CFDUMP shows correctly instantiated object
 
	s3 = CreateObject(	'java',
		'com.amazonaws.services.s3.AmazonS3Client'
		).init(awsCred);
// this line throws the error

Any ideas how to instantiate a real Java object?

Thanks
James

Ignore my earlier post, it appears that the Amazon SDK requires some more third party Jar files in the class path than it comes with, namely httpclient-4.1.1.jar if you're having similar problems.