XOM API for Processing XML with Java

[adamc AT email.unc.edu]

Quoting David Ondzes <dondzes AT gmail.com>:

> Hello All. I am relatively new to XML programming. While looking for
> an easy to use/getting started XML package I found XOM. I am trying to
> write an app that reads XML from a socket connection and I am getting
>
> "[Fatal Error] :1:1: Content is not allowed in prolog."

That exception message refers specifically to having some text that 
isn't XML markup before the first element.  Depending on *how* the text 
you're trying to parse is streamed to you, that well might be the cause 
of the problem you're seeing.  For example, if you're getting it "raw" 
over HTTP, the response stream will contain the HTTP headers before the 
XML text.

My suggestion is to try reading the stream first without using 
XOM/Xerces to parse it, and dumping the results to a file or the 
console.  This way, you'll be able to see what it is that Xerces (which 
is XOM's default XML parser) is trying to parse.

The first part of your document should be something like what's inside 
the triple quotes below:

"""<?xml version="1.0" encoding="utf-8"?>
<root>
"""

The first line (the XML declaration) is strictly speaking optional, but 
if it's not there the first text in the stream Xerces is trying to 
parse MUST be the root element or a DOCTYPE declaration (which looks 
like """<!DOCTYPE ...""")

Anything else at the beginning of the document and Xerces will 
(rightfully!) complain.

HTH

AC