GeoTools

OSGeo

Previous topic

OpenGIS FAQ

Next topic

FeatureType

This Page

ModelΒΆ

GeoTools provides a clear separation between:

  • data model - feature responsible for holding values
  • query model - filter and expression used to select content and drill in and retrieve values
  • metadata model - feature type describing contents in sufficient details for validation and query construction

References:

Comparison to Java:

  • The data structure Feature is used to hold information. Each Feature “belongs to” a FeatureType which is used to describe valid contents. This is a dynamic type system because FeatureType is a data structure we can define at runtime.
  • The data structure Object is used to hold information. Each Object “belongs to” a Class which is used to describe valid contents. This is a static type system because Class is a data structure we need to compile before the application is started.
Java Class System GeoTools Feature Model Java Beans System
static type system dynamic type system dynamic type system
Object SimpleFeature Object
(reflection) Attribute (reflection)
(reflection) GeometryAttribute (reflection)
Class SimpleFeatureType BeanInfo
Field AttributeDescriptor PropertyDescriptor
Field GeometryAttributeDescriptor PropertyDescriptor
Method OperationType MethodDescriptor
Field.getType() AttributeDescriptor.getType().getBinding() PropertyDescriptor.getPropertyType()
Field.getName() AttributeDescriptor.getName().getLocalName() PropertyDescriptor.getName()
Field.get( obj ) expression.evaulate( feature, Class ) descriptor.getReadMethod().invoke(obj)

Java example:

class Flag {
    public Point location;
    public String name;
    public int classification;
    public double height;
 };

 GeometryFactory geomFactory = JTSFactoryFinder.getGeometryFactory();

 Flag here = new Flag();
 here.location = geomFactory.createPoint( new Coordinate(23.3,-37.2) );
 here.name = "Here";
 here.classification = 3;
 here.height = 2.0;

Feature example:

SimpleFeatureTypeBuilder b = new SimpleFeatureTypeBuilder();
b.setName( "Flag" );
b.setCRS( DefaultGeographicCRS.WGS84 );
b.add( "location", Point.class );
b.add( "name", String.class );
b.add( "classification", Integer.class );
b.add( "height", Double.class );
SimpleFeatureType type = b.buildFeatureType();

GeometryFactory geomFactory = JTSFactoryFinder.getGeometryFactory();

SimpleFeatureBuilder f = new SimpleFeatureBuilder( type );
f.add( geomFactory.createPoint( new Coordinate(23.3,-37.2) ) );
f.add("here");
f.add(3);
f.add(2.0);
SimpleFeature feature = f.buildFeature("fid.1");