01 SAX Parser

SAX is an event based system, to use SAX directly GeoTools (actually Rob Hranac) defined a series of ContentHandlers:

org.geotools.gml: GMLHandlerJTS, GMLHandlerGeometry, GMLHandlerFeature
etc ...

Levels

To make matters exciting the Content Handlers are defined at different "levels" - lets use GML as an example:

	Interface	Class	Purpose
LEVEL 1	raw sax	GMLFilterDocument	basic alerts for GML types; to ...
LEVEL 2	GMLHandlerGeometry	GMLHandlerGeometry	GMLFilterGeometry - translates coordinates and GML events into OGC simple types; for ...
LEVEL 3	GMLHandlerJTS	GMLFilterFeature	translates JTS elements and attributes into features
LEVEL 4	GMLHandlerFeature	your code	accepts features

You can see that in order to use literal JTS Geometries the SAX Filter parser will need to implement GMLHandlerJTS:

Example Code with Filter

First of all we need a Handler to catch the result, a Filter Handler

public class SimpleFilterHandler extends DefaultHandler implements FilterHandler {
  private Filter filter;
  public void filter(Filter filter) {
    this.filter = filter;
  }
  public Filter getFilter() {
    return filter;
  }
}

And then we can get down to actual parsing:

public Filter parse(InputSource input) throws IOException, SAXException {
    SimpleFilterHandler simpleFilterHandler = new SimpleFilterHandler();
    FilterFilter filterFilter = new FilterFilter(simpleFilterHandler, null);
    GMLFilterGeometry filterGeometry = new GMLFilterGeometry(filterFilter);
    GMLFilterDocument filterDocument = new GMLFilterDocument(filterGeometry);

    // parse xml
    XMLReader reader = XMLReaderFactory.createXMLReader();
    reader.setContentHandler(filterDocument);
    reader.parse(input);
    
    return simpleFilterHandler.getFilter();
}

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01 SAX Parser

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Levels

Example Code with Filter

Serialization of XMLNS attributes