Receiving Input data

I send a String to a WM service using a ServerXMLHTTP object in ASP. This service is really simple. It gets a String in input and modifies it. But each time I call it (by sending a file with my ASP page), I get a NullPointerException error.
I don’t know how to debug that, as I can’t see the value of my input string. Should I use a node…? How…?
Any idea someone?

I assume your service is written in Java.

Add a:
or if you are using <3.5 style service signatures:

as the first line of your service. If the XML file is POSTed to the service, then it will appear in the pipeline as a Object node, which you can operate on using the services in WmPublic pub.web.