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Filter

No utility class, this time out we will be making direct use of the three available GTXML configurations:

  • org.geotools.filter.v1_0.OGCConfiguration
  • org.geotools.filter.v1_1.OGCConfiguration
  • org.geotools.filter.v2_0.FESConfiguration

The definition of filter is considered part of the ogc schema, hence the use of OGCConfiguration above.

Filter1

The Filter 1.0 specification is supported by SAX, DOM and GTXML.

Note

Filter 1.0 specification requires the use of GML2 to represent Geometry elements.

Encode

To encode a filter:

org.geotools.xml.Configuration = new org.geotools.filter.v1_0.OGCConfiguration();
org.geotools.xml.Encoder encoder = new org.geotools.xml.Encoder( configuration );
encoder.encode( filter, org.geotools.filter.v1_0.OGC.FILTER, outputStream );

This configurations bring in the correct GML2 version of GMLConfiguration to handle any geometry mentioned in your Filter.

Consider the following filter:

FilterFactory ff = CommonFactoryFinder.getFilterFactory( null );
PropertyName propertyName = ff.property( "testString" );
Literal literal = ff.literal( 2 );
PropertyIsEqualTo filter = ff.equals( propertyName, literal );

To encode the filter:

//create the encoder with the filter 1.0 configuration
org.geotools.xml.Configuration = new org.geotools.filter.v1_0.OGCConfiguration();
org.geotools.xml.Encoder encoder = new org.geotools.xml.Encoder( configuration );

//create an output stream
OutputStream xml = ...

//encode
encoder.encode( filter, org.geotools.filter.v1_0.OGC.FILTER, xml );

Parser

To parse a filter:

Configuration configuration = new org.geotools.filter.v1_0.OGCConfiguration();
Parser parser = new Parser( configuration );

Filter filter = (Filter) parser.parse( imputStream );

Consider the following filter document:

<Filter xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:ogc="http://www.opengis.net/ogc"
  xmlns="http://www.opengis.net/ogc"
  xsi:schemaLocation="http://www.opengis.net/ogc filter.xsd">
  <PropertyIsEqualTo>
    <PropertyName>testString</PropertyName>
    <Literal>2</Literal>
  </PropertyIsEqualTo>
</Filter>

To parse the document:

//create the parser with the filter 1.0 configuration
Configuration configuration = new org.geotools.filter.v1_0.OGCConfiguration();
Parser parser = new Parser( configuration );

//the xml instance document above
InputStream xml = ...

//parse
Filter filter = (Filter) parser.parse( xml );

FilterFilter (SAX)

An alternative to using a GTXML configuration is to directly handle the SAX events yourself.

As mentioned n the previous page on geometry page sax events involve defining a callback class that can be invoked as each Filter is recognised.

Here is a quick example:

    
    class SimpleFilterHandler extends DefaultHandler implements FilterHandler {
    public Filter filter;
    
    public void filter(Filter filter) {
        this.filter = filter;
    }
    }
    
    SimpleFilterHandler simpleFilterHandler = new SimpleFilterHandler();
    FilterFilter filterFilter = new FilterFilter(simpleFilterHandler, featureType);
    GMLFilterGeometry filterGeometry = new GMLFilterGeometry(filterFilter);
    GMLFilterDocument filterDocument = new GMLFilterDocument(filterGeometry);
    
    // parse xml
    XMLReader reader = XMLReaderFactory.createXMLReader();
    reader.setContentHandler(filterDocument);
    reader.parse(input);
    Filter filter = simpleFilterHandler.filter;

FilterDOMParser DOM

DOM based parsers are useful if your application already is working with DOM. An example would be parsing an Style object out of an Web Map Server GetMap request.

You can use the DOM parser to parse individual filter nodes:

InputSource input = new InputSource( reader );

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document dom = db.parse( input );

Filter filter = null;

// first grab a filter node
NodeList nodes = dom.getElementsByTagName("Filter");

for (int j = 0; j < nodes.getLength(); j++) {
    Element filterNode = (Element) nodes.item(j);
    NodeList list = filterNode.getChildNodes();
    Node child = null;

    for (int i = 0; i < list.getLength(); i++) {
        child = list.item(i);

        if ((child == null) || (child.getNodeType() != Node.ELEMENT_NODE)) {
            continue;
        }

        filter = FilterDOMParser.parseFilter(child);
  }
}
System.out.println( "got:"+filter );

Filter 1.1

The Filter 1.1 specification is provided by v1_1 OGCConfiguration.

Note

Filter 1.1 uses GML3 to represent Geometry as required by the specification.

Ecode

To encode a filter:

org.geotools.xml.Configuration = new org.geotools.filter.v1_1.OGCConfiguration();
org.geotools.xml.Encoder encoder = new org.geotools.xml.Encoder( configuration );
encoder.encode( filter, org.geotools.filter.v1_0.OGC.FILTER, outputStream );

Parse

To parse a filter:

Configuration configuration = new org.geotools.filter.v1_1.OGCConfiguration();
Parser parser = new Parser( configuration );

Filter filter = (Filter) parser.parse( imputStream );

Filter2

The Filter 2.0 specification is provided by v2_0 FESConfiguration.

Parse

Sample document:

<fes:Filter
   xmlns:fes='http://www.opengis.net/fes/2.0'
   xmlns:gml='http://www.opengis.net/gml/3.2'
   xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
   xsi:schemaLocation='http://www.opengis.net/fes/2.0 http://schemas.opengis.net/filter/2.0/filterAll.xsd
 http://www.opengis.net/gml/3.2 http://schemas.opengis.net/gml/3.2.1/gml.xsd'>
   <fes:TOverlaps>
      <fes:ValueReference>timeInstanceAttribute</fes:ValueReference>
   <gml:TimePeriod gml:id='TP1'>
      <gml:begin>
        <gml:TimeInstant gml:id='TI1'>
          <gml:timePosition>2005-05-17T08:00:00Z</gml:timePosition>
        </gml:TimeInstant>
      </gml:begin>
      <gml:end>
        <gml:TimeInstant gml:id='TI2'>
          <gml:timePosition>2005-05-23T11:00:00Z</gml:timePosition>
        </gml:TimeInstant>
      </gml:end>
    </gml:TimePeriod>
   </fes:TOverlaps>
</fes:Filter>

Parsing:

Configuration configuration = new org.geotools.filter.v2_0.FESConfiguration();
Parser parser = new Parser( configuration );

Filter filter = (Filter) parser.parse( imputStream );

Encode:

org.geotools.xml.Configuration = new org.geotools.filter.v2_0.FESConfiguration();
org.geotools.xml.Encoder encoder = new org.geotools.xml.Encoder( configuration );
encoder.encode( org.geotools.filter.v2_0.FES.Filter, outputStream );