Main FAQ

Q: What is gt-main responsible for?

The gt-main module defines the following API:

• org.geotools.jts for integrating with the JTS Topology Suite representing geometry.

• org.geotools.api.data which defines a datastore api to read and write spatial content

In addition gt-main modules includes the default implementations for the feature model, filter support, and style data structures. These default implementations are not intended to be used directly, and are accessed through the plug-in system. Implementation access is provided by CommonFactoryFinder and DataStoreFinder rather than creating new instances.

Q: How do I make a FeatureType?

Use FeatureTypeBuilde to define a feature type:

SimpleFeatureTypeBuilder b = new SimpleFeatureTypeBuilder();

//set the name
b.setName( "Flag" );

//add some properties
b.add( "name", String.class );
b.add( "classification", Integer.class );
b.add( "height", Double.class );

//add a geometry property
b.setCRS( DefaultGeographicCRS.WSG84 ); // set crs first
b.add( "location", Point.class ); // then add geometry

//build the type
final SimpleFeatureType FLAG = b.buildFeatureType();

You may also see Test cases using the DataUtilities createType method (which processes a text string and calls SimpleFeatureType builder):

SimpleFeatureType lineType = DataUtilities.createType("LINE", "centerline:LineString,name:\"\",id:0");

Q: How do I modify a FeatureType?

You cannot modify a feature type directly as it is considered immutable and not subject to change.

You can however use a FeatureTypeBuilder to create a modified copy:

SimpleFeatureType lineType = DataUtilities.createType("LINE", "geom:LineString,name:\"\",id:0");
SimpleFeatureTypeBuilder b = new SimpleFeatureTypeBuilder();
b.init( lineType );
b.setName("POINT");
b.add(0, "geom", Point.class );
SimpleFeatureType pointType = b.buildFeatureType();

Q: How to get FeatureCollection to work with a ‘for each’ loop?

Feature collection is a wrapper around a live data stream; as such we need to be sure to close the iterator after we are finished with it:

        try (SimpleFeatureIterator iterator = featureCollection.features()) {
            while (iterator.hasNext()) {
                SimpleFeature feature = iterator.next();
                // process feature
            }
        }

This requirement prevents us implementing Collection (and being compatible with ‘for each’ syntax. I am afraid this is a fundamental limitation of Java and not something that can or should be addressed in a future release.