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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();
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 |
---|
Name getName()
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).
FeatureSource
ResourceInfo getInfo()
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().
DataAccess<T,F> getDataStore()
DataAccess
object, providing
this FeatureSource
.
FeatureSource
QueryCapabilities getQueryCapabilities()
FeatureSource
natively supports. For example, whether queries can return sorted
results.
FeatureSource
void addFeatureListener(FeatureListener listener)
FeatureSource
.
listener
- the new listenervoid removeFeatureListener(FeatureListener listener)
FeatureSource's
listeners.
listener
- the listener to removeFeatureCollection<T,F> getFeatures(Filter filter) throws IOException
FeatureCollection
, based
on an OGC Filter
.
filter
- the filter to select features; must not be null
(use Filter.INCLUDE instead)
Filter
IOException
- if the underlying data source cannot be accessed.Filter
FeatureCollection<T,F> getFeatures(Query query) throws IOException
FeatureCollection
, based
on a Query
.
query
- DataAccess query for requested information, such as typeName,
maxFeatures and filter.
Query
IOException
- if the underlying data source cannot be accessed.Query
FeatureCollection<T,F> getFeatures() throws IOException
FeatureCollection
.
The following statements are equivalent:
featureSource.getFeatures();
featureSource.getFeatures(Filter.INCLUDE);
featureSource.getFeatures(Query.ALL);
Query
IOException
- if the underlying data source cannot be accessed.T getSchema()
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.
FeatureSource
ReferencedEnvelope getBounds() throws IOException
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.
null
if the bounds are unknown or too costly to calculate.
IOException
- on any errors calculating the boundsReferencedEnvelope getBounds(Query query) throws IOException
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.
query
- the query to select features
null
if the bounds are unknown or too costly to calculate.
IOException
- on any errors calculating the boundsint getCount(Query query) throws IOException
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
Set<RenderingHints.Key> getSupportedHints()
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.
RenderingHints#Key
objects; may be empty but never null
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
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