Model

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:

• FeatureType
• Feature
• gt-main feature code examples
• gt-main filter code examples

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");