[Geotools-devel] IRC feedback - SLD parser

[Chris H. <ch...@op...>]

Was supposed to email this yesterday, but had to get off the internet...

My first big beef with the current sld parser is it uses DOM Filter
parsing.  I think the DOM SLD parsing is decent, but it kills me
whenever I have to maintain the DOM Filter parser.  I have spent a
_ton_ of time getting the SAX Filter parsing working perfectly (ok, as
good as it can without lazy loading).  GeoServer has done a massive QA
job on it.  It should be able to handle all the Filters in SLD that it
handles in WFS.  So that's why I personally cringe every time I use it.

One small correction on David's bit about validating.  We're not yet
validating against the schema in GeoServer.  That's my last thing to do
if we're still going to be working with the DOM parser.  But it's a bit
more tricky then I thought at first, since we'd need to get it to
reference our schema file, since often the schema file of an user
defined SLD will be wrong, or at least without a schemaLocation.  Of
course the XDO makes this trivial, but we're not yet using that parser.
 So what I check now is just that there are no SAX errors, and that the
DOM doesn't completely choke.  Problem is the DOM SLD parser will _not_
give you any sort of meaningful message if you pass it say a
describe.xml file (which I did).  It will just not return a Style.  But
it won't even say that it couldn't find a UserStyle element.  It will
just return nulls, it won't return errors.  Basically from a GeoServer
perspective we should be able to generate meaningful errors to help
correct what might be wrong with the SLD files that users try to
submit.    I am not yet convinced that XDO does this well, since the
only error messages I've seen out of it (personally, and I admit I've
not used it much), are extraordinarily unhelpful.  Personally if I had
the time and inclination to do this I'd use SAX, or maybe check out the
streaming xml parser that Jody and them found, that does most
everything well except the schema support.

Chris


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