<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>

//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 );

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

//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 );