[flexcoders] How to properly pass an error from Java to Flex client

[Collin Peters]

We have an FDS Java backend (haven't upgrade to LCDS or Blaze yet) and
I am wondering how to properly throw exceptions from Java to the
client.

So if the backend encounters any exception (RuntimeException,
NullPointerException, etc...) the fault method of my responder gets
called and passes in a FaultEvent object.  This contains a Fault
object and a ErrorMessage object but none of those contain any useful
information.  If I have the Java code to test this as:
                if(true)
                {
                        throw new RuntimeException("foobar");
                }

Then in my Fault object I get:
faultCode = "Server.Processing"
faultDetail = null
faultString = "java.lang.RuntimeException : foobar"

This is pretty much useless on the Flex side.  To parse out the
message I have to do some string parsing, etc...  How do you properly
return an error to the client?  How can I set the values of faultCode,
faultDetail, faultString, errorID, etc...?