On 10/14/2011 7:00 AM, coffeMan wrote:
> I am retrieving XML from a servlet and parsing through it. the xml
> code is one large XML file but on through the servlet. I can parse
> through it easy and get my results but i am not sure when to stop it.
> I keep getting NullPointerException that kicks off when it reaches the
> end. I never know when its going to end because every file that i
> parse through is different in length.
>
> I am using the DOM parser. Document messageDom =
> XMLParser.parse(srv.getXmlObject());
>
> string name =
> messageDom.getElementsByTagName("name").item(n).getFirstChild().getNodeValue();
> - n being a variable that is an integer value that increases after
> each loop
A couple of questions come to mind:
1) Are you sure the document is valid? Does there exist an XML schema
against which you can test this document instance? If not, you might
consider creating an XML schema, a sample document, and running the pair
through a validating parser such as xmllint. Such validation tests can
be a useful part of your overall product verification/validation regime.
2) Have you considered using GQuery to produce nodelists? For complex,
valid documents it can be a useful tool.
3) Consider using loops controlled by NodeList.length() instead of using
the builder pattern to process the tree. In my experience, using loops
instead of the builder pattern yields fewer surprises at runtime. I
realize there's a "cool factor" to chaining those method calls, but it
usually results in issues such as the one you're now trying to resolve.
Bueno Suerte,
jec
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