org.geotools.data
Interface FeatureSource<T extends FeatureType,F extends Feature>

All Known Subinterfaces:

FeatureLocking<T,F>, FeatureStore<T,F>, SimpleFeatureLocking, SimpleFeatureSource, SimpleFeatureStore, XmlFeatureSource

All Known Implementing Classes:

AbstractFeatureLocking, AbstractFeatureSource, AbstractFeatureStore, ArcSdeFeatureSource, ArcSdeFeatureStore, CachingFeatureSource, CollectionFeatureSource, ContentFeatureSource, ContentFeatureStore, DefaultView, DirectoryFeatureLocking, DirectoryFeatureSource, DirectoryFeatureStore, JDBCFeatureSource, JDBCFeatureStore, JoiningJDBCFeatureSource, MappingFeatureSource, PreGeneralizedFeatureSource, PropertyFeatureSource, PropertyFeatureStore, SampleDataAccessFeatureSource, ShapefileFeatureLocking, ShapefileFeatureStore, SpatialIndexFeatureSource, WFSFeatureSource, WFSFeatureSource, WFSFeatureStore

public interface FeatureSource<T extends FeatureType,F extends Feature>

This class provides a high-level API for operations on feature data. Typically, when working with a data source such as a shapefile or database table you will initially create a DataStore object to connect to the physical source and then retrieve a FeatureSource to work with the feature data, as in this excerpt from the GeoTools Quickstart example (http://geotools.org/quickstart.html)

     File file = ...
     FileDataStore store = FileDataStoreFinder.getDataStore(file);
     FeatureSource featureSource = store.getFeatureSource();
 

Author:

Jody Garnett, Ray Gallagher, Rob Hranac, TOPP, Chris Holmes, TOPP

See Also:

DataStore

Method Summary

void	addFeatureListener(FeatureListener listener) Registers a listening object that will be notified of changes to this FeatureSource.
ReferencedEnvelope	getBounds() Get the spatial bounds of the feature data.
ReferencedEnvelope	getBounds(Query query) Get the spatial bounds of the features that would be returned by the given Query.
int	getCount(Query query) Gets the number of the features that would be returned by the given Query, taking into account any settings for max features and start index set on the Query.
DataAccess<T,F>	getDataStore() Returns the data source, as a DataAccess object, providing this FeatureSource.
FeatureCollection<T,F>	getFeatures() Retrieves all features in the form of a FeatureCollection.
FeatureCollection<T,F>	getFeatures(Filter filter) Retrieves features, in the form of a FeatureCollection, based on an OGC Filter.
FeatureCollection<T,F>	getFeatures(Query query) Retrieves features, in the form of a FeatureCollection, based on a Query.
ResourceInfo	getInfo() Returns information describing this FeatureSource which may include title, description and spatial parameters.
Name	getName() Returns the name of the features (strictly, the name of the AttributeDescriptor for the features) accessible through this FeatureSource.
QueryCapabilities	getQueryCapabilities() Enquire what what query capabilities this FeatureSource natively supports.
T	getSchema() Retrieves the schema (feature type) that will apply to features retrieved from this FeatureSource.
Set<RenderingHints.Key>	getSupportedHints() Returns the set of hints that this FeatureSource supports via Query requests.
void	removeFeatureListener(FeatureListener listener) Removes an object from this FeatureSource's listeners.

Method Detail

getName

Name getName()

Returns the name of the features (strictly, the name of the AttributeDescriptor for the features) accessible through this FeatureSource.

The value returned by this method can be different to that returned by featureSource.getSchema().getType().getName(). This is because there is a distinction between the name applied to features and the name of a feature type. When working with SimpleFeature and SimpleFeatureType, for example with a shapefile data source, it is common practice for feature and feature type names to be the same. However, this is not the case more generally. For instance, a database can contain two tables with the same structure. The feature name will refer to the table while the feature type name refers to the schema (table structure).

Returns:

the name of the features accessible through this FeatureSource

Since:

2.5

getInfo

ResourceInfo getInfo()

Returns information describing this FeatureSource which may include title, description and spatial parameters. Note that in the returned ResourceInfo object, the distinction between feature name and schema (feature type) name applies as discussed for getName().

getDataStore

DataAccess<T,F> getDataStore()

Returns the data source, as a DataAccess object, providing this FeatureSource.

Returns:

the data source providing this FeatureSource

getQueryCapabilities

QueryCapabilities getQueryCapabilities()

Enquire what what query capabilities this FeatureSource natively supports. For example, whether queries can return sorted results.

Returns:

the native query capabilities of this FeatureSource

Since:

2.5

addFeatureListener

void addFeatureListener(FeatureListener listener)

Registers a listening object that will be notified of changes to this FeatureSource.

Parameters:

listener - the new listener

removeFeatureListener

void removeFeatureListener(FeatureListener listener)

Removes an object from this FeatureSource's listeners.

Parameters:

listener - the listener to remove

getFeatures

FeatureCollection<T,F> getFeatures(Filter filter)
                                                                       throws IOException

Retrieves features, in the form of a FeatureCollection, based on an OGC Filter.

Parameters:

filter - the filter to select features; must not be null (use Filter.INCLUDE instead)

Returns:

features retrieved by the Filter

Throws:

IOException - if the underlying data source cannot be accessed.

See Also:

Filter

getFeatures

FeatureCollection<T,F> getFeatures(Query query)
                                                                       throws IOException

Retrieves features, in the form of a FeatureCollection, based on a Query.

Parameters:

query - DataAccess query for requested information, such as typeName, maxFeatures and filter.

Returns:

features retrieved by the Query

Throws:

IOException - if the underlying data source cannot be accessed.

See Also:

Query

getFeatures

FeatureCollection<T,F> getFeatures()
                                                                       throws IOException

Retrieves all features in the form of a FeatureCollection.

The following statements are equivalent:

     featureSource.getFeatures();
     featureSource.getFeatures(Filter.INCLUDE);
     featureSource.getFeatures(Query.ALL);
 

Returns:

features retrieved by the Query

Throws:

IOException - if the underlying data source cannot be accessed.

getSchema

T getSchema()

Retrieves the schema (feature type) that will apply to features retrieved from this FeatureSource.

For a homogeneous data source such as a shapefile or a database table, this schema be that of all features. For a heterogeneous data source, e.g. a GML document, the schema returned is the lowest common denominator across all features.

Returns:

the schema that will apply to features retrieved from this FeatureSource

getBounds

ReferencedEnvelope getBounds()
                             throws IOException

Get the spatial bounds of the feature data. This is equivalent to calling getBounds(Query.ALL).

It is possible that this method will return null if the calculation of bounds is judged to be too costly by the implementing class. In this case, you might call getFeatures().getBounds() instead.

Returns:

The bounding envelope of the feature data; or null if the bounds are unknown or too costly to calculate.

Throws:

IOException - on any errors calculating the bounds

getBounds

ReferencedEnvelope getBounds(Query query)
                             throws IOException

Get the spatial bounds of the features that would be returned by the given Query.

It is possible that this method will return null if the calculation of bounds is judged to be too costly by the implementing class. In this case, you might call getFeatures(query).getBounds() instead.

Parameters:

query - the query to select features

Returns:

The bounding envelope of the feature data; or null if the bounds are unknown or too costly to calculate.

Throws:

IOException - on any errors calculating the bounds

getCount

int getCount(Query query)
             throws IOException

Gets the number of the features that would be returned by the given Query, taking into account any settings for max features and start index set on the Query.

It is possible that this method will return -1 if the calculation of number of features is judged to be too costly by the implementing class. In this case, you might call getFeatures(query).size() instead.

Example use:

 int count = featureSource.getCount();
 if( count == -1 ){
    count = featureSource.getFeatures( "typeName", count ).size();
 }


Parameters:
query - the query to select features
Returns:
the numer of features that would be returned by the Query;
         or -1 if this cannot be calculated.
Throws:
IOException - if there are errors getting the count

getSupportedHints

Set<RenderingHints.Key> getSupportedHints()

Returns the set of hints that this FeatureSource supports via Query requests.

Note: the existence of a specific hint does not guarantee that it will always be honored by the implementing class.

Returns:

a set of RenderingHints#Key objects; may be empty but never null

See Also:

Hints.FEATURE_DETACHED, Hints.JTS_GEOMETRY_FACTORY, Hints.JTS_COORDINATE_SEQUENCE_FACTORY, Hints.JTS_PRECISION_MODEL, Hints.JTS_SRID, Hints.GEOMETRY_DISTANCE, Hints.FEATURE_2D