[OpenLayers-Users] Extract/read attributes from GML

[springrider]

Effectively, it was a namespace problem.

This is my finalized code to obtain the current extent of my polygons.Could
be useful to someone else:

                  g =  new OpenLayers.Format.GML();
		  features = g.read(req.responseText);		  
		  for (var i=0;i<features.length;i++) {
			var feature = features[i];			
			var bounds = feature.geometry.getBounds();
			if (i==0){
				var minx=bounds.left;
				var miny=bounds.bottom;
				var maxx=bounds.right;
				var maxy=bounds.top;
			}
                   minx = Math.min(minx, bounds.left);
		   miny = Math.min(miny, bounds.bottom);
                   maxx = Math.max(maxx, bounds.right);
                   maxy = Math.max(maxy, bounds.top);
			} 
		   alert(minx & " " & miny & " " & maxx & " " & maxy);	
		   map.zoomToExtent(new OpenLayers.Bounds(minx, miny, maxx, maxy));

It works beautifully to extract the extent of my displayed polygons

Thanks

Sylvain



Arnd Wippermann wrote:
> 
> Hi,
> propably you have problems with the namespaces. This is, what I get when I
> load the gml with IE6:
>  
> The XML page cannot be displayed 
> Cannot view XML input using XSL style sheet. Please correct the error and
> then click the Refresh button, or try again later. 
> 
> 
> ----------------------------------------------------------------------------
> ----
> 
> Reference to undeclared namespace prefix: 'wfs'. Error processing resource
> 'http://www.nabble.com/file/p13750828/gml.xml'. ...
> 
> <wfs:FeatureCollection xsi:schemaLocation="http://www.fao.org/fi
> http://193.43.36.238:8282/geoserver/wfs/DescribeFeatureT...
> 
> 
> Mit freundlichen Grüssen
> 
> Arnd Wippermann
> http://gis.ibbeck.de/ginfo/
> 
> 
> 
> -----Ursprüngliche Nachricht-----
> Von: users-bounces at openlayers.org [mailto:users-bounces at openlayers.org] Im
> Auftrag von springrider
> Gesendet: Mittwoch, 14. November 2007 17:44
> An: users at openlayers.org
> Betreff: Re: [OpenLayers-Users] Extract/read attributes from GML
> 
> 
> Thanks for your answer
> 
> I think i was not clear, I used to be a XML/XSL developper so i wanted to
> access this specific tag. After browsing the different examples and mainly
> the GMLparser example, i found some answers. I can obtain using OL code
> the
> bouding box of my polygon directly.
> 
> This is a my current code:
> 
> g =  new OpenLayers.Format.GML();
> features = g.read(req.responseText);
> var bounds = features[1].geometry.getBounds();
> 
> It works fine with the XMLs available for this OL example but with my GML,
> i
> always have features.length=0. By doing Alert(req.responseText), i obtain
> effectively my GML but no features are considered in it. In attachment,
> you
> will find my GML: http://www.nabble.com/file/p13750828/gml.xml gml.xml .
> 
> I really hope you can help me.
> 
> Thanks
> 
> Sylvain
> 
> 
> 
> Christopher Schmidt-4 wrote:
>> 
>> On Wed, Nov 14, 2007 at 07:17:08AM -0800, springrider wrote:
>>> 
>>> Good morning
>>> 
>>> I would be interested to extract/read text within some tags
>>> (wfs:FeatureCollection\gml:boundedBy\gml:Box\gml:coordinates) from my 
>>> GML. I am now struggling trying to write the correct syntax. I tried 
>>> something like
>>> that:
>>>  var myGml= new
>>> OpenLayers.Layer.GML("myGML","http://193.43.36.238:8282/geoserver/wfs
>>> ?request=GetFeature&typename=fifao:Fao_areas&cql_filter=F_AREA=27");
>>> var myExtent=
>>> myGml.read("wfs:FeatureCollection\gml:boundedBy\gml:Box\gml:coordinat
>>> es")
>>> 
>>> But it is not correct.Could you please help me? I would then use this 
>>> text to define the extent of my map.
>> 
>> This isn't going to do what you want it to do.
>> 
>> 1. None of the OpenLayers libraries include support for xpath like 
>> navigation of XML documents.
>> 2. The GML parser returns features; additional metadata from the 
>> document is ignored.
>> 3. The Layer is just about displaying data; you're more likely to want 
>> to use the Format (but it still won't do what you want.)
>> 
>> You'll probably want to use the Format.XML class to load the data, and 
>> use standard DOM methods to manipulate the loaded XML, or the 
>> Format.XML specific getElementsByTagNameNS and the like.
>> 
>> OpenLayers is a map library, rather than a geodata management 
>> framework, so it doesn't provide the tools to do what you want easily, 
>> as far as I'm aware.
>> 
>> Regards,
>> --
>> Christopher Schmidt
>> MetaCarta
>> _______________________________________________
>> Users mailing list
>> Users at openlayers.org
>> http://openlayers.org/mailman/listinfo/users
>> 
>> 
> 
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