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");

GeoTools

OSGeo

Model¶