org.geotools.feature

Stores metadata about a single attribute object.

1. Name: A string that is used to reference the attribute.
2. Nillable: if nulls are allowed as this attribute.
3. Type: The expected Java class of this attribute.

AttributeTypes must also provide the validate(Object obj) method, which determines whether a given object matches the constraints imposed by the AttributeType.

Proposal: AttributeType utilities class.

Represents a feature of arbitrary complexity.

This interface answers the question: How do we store feature attributes? (The answer to the more useful question, How do we access feature attribute, is contained in the Expression class.

Warning: We are revising the Feature Model to be more complete in the next round of GeoTools.

While we could use a plain AttributeType to capture a Feature instance we would miss out one one important aspect: the schema.

By definition the schema of a Feature is not defined by java interface alone, this interface allows access the the assocaited FeatureType.

Suggestion: we can look at having this class extend ListFeatureType and exactly specifying how delegation to the getSchema() should occur.

Implementations (and client code) should adhere to the rules set forth by java.util.Collection.

Geotools 2.0: As Features always require a FeatureType the best place to implement this is in the FeatureType itself, thus the FeatureType interface extends this interface.

An object in a column can be any object, but must either be a java base-type Object (Integer, String, Character, etc.) or implement Comparable.

An Index built on such a column will sort its array of object references using FeatureComparator.

A FeatureList is usually retrived from a FeatureCollection with the subCollection( Filter ) operation.

Notes:

• that this documentation should be read in conjunction with the Feature API.
• the attributes described by this FeatureType and its ancestors define the complete schema for a Feature

  This interface answers the question: How do we represent features within GeoTools? Of course, the most general answer would be: features can be any Java object.

The basic idea for usage is that you configure the builder to whatever state is desired, setting properties and adding AttributeTypes.

This class is the bridge between our FeatureType/AttributeType classes and the CoordianteSystem.

This also allows access to the GeometryFactory used by this GeometryAttributeType parse( Object ) method.

With JTS14 you can use GeometryFactory to to provide your own CoordianteSequence representation.

These methods are often used for implementation the convience methods such as FeatureType.getAttributeCount(), although they may be used directly with any FeatureType.

These schema methods are based on the *complete* picture indicated by a FeatureType and its ancestors.