| FeatureSource.java |
/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.data;
import java.awt.RenderingHints;
import java.io.IOException;
import java.util.Set;
import org.geotools.factory.Hints;
import org.geotools.feature.FeatureCollection;
import org.geotools.geometry.jts.ReferencedEnvelope;
import org.opengis.feature.Feature;
import org.opengis.feature.type.FeatureType;
import org.opengis.feature.type.Name;
import org.opengis.filter.Filter;
/**
* 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 {@code DataStore} object to connect
* to the physical source and then retrieve a {@code FeatureSource} to work with
* the feature data, as in this excerpt from the GeoTools Quickstart example
* (<a href="http://geotools.org/quickstart.html">http://geotools.org/quickstart.html</a>)
* <pre><code>
* File file = ...
* FileDataStore store = FileDataStoreFinder.getDataStore(file);
* FeatureSource featureSource = store.getFeatureSource();
* </code></pre>
* @see DataStore
*
* @author Jody Garnett
* @author Ray Gallagher
* @author Rob Hranac, TOPP
* @author Chris Holmes, TOPP
* @source $URL: http://svn.osgeo.org/geotools/tags/2.7-M3/modules/library/api/src/main/java/org/geotools/data/FeatureSource.java $
* @version $Id: FeatureSource.java 35550 2010-05-23 03:42:20Z jive $
*/
public interface FeatureSource<T extends FeatureType, F extends Feature>{
/**
* Returns the name of the features (strictly, the name of the
* {@code AttributeDescriptor} for the features) accessible through this
* {@code FeatureSource}.
* <p>
* The value returned by this method can be different to that returned by
* {@code 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 {@code SimpleFeature} and
* {@code 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).
*
* @since 2.5
* @return the name of the features accessible through this {@code FeatureSource}
*/
Name getName();
/**
* Returns information describing this {@code FeatureSource} which may
* include title, description and spatial parameters. Note that in the
* returned {@code ResourceInfo} object, the distinction between feature
* name and schema (feature type) name applies as discussed for
* {@linkplain #getName()}.
*/
ResourceInfo getInfo();
/**
* Returns the data source, as a {@code DataAccess} object, providing
* this {@code FeatureSource}.
*
* @return the data source providing this {@code FeatureSource}
*/
DataAccess<T, F> getDataStore();
/**
* Enquire what what query capabilities this {@code FeatureSource}
* natively supports. For example, whether queries can return sorted
* results.
*
* @return the native query capabilities of this {@code FeatureSource}
* @since 2.5
*/
QueryCapabilities getQueryCapabilities();
/**
* Registers a listening object that will be notified of changes to this
* {@code FeatureSource}.
*
* @param listener the new listener
*/
void addFeatureListener(FeatureListener listener);
/**
* Removes an object from this {@code FeatureSource's} listeners.
*
* @param listener the listener to remove
*/
void removeFeatureListener(FeatureListener listener);
/**
* Retrieves features, in the form of a {@code FeatureCollection}, based
* on an OGC {@code Filter}.
*
* @param filter the filter to select features; must not be {@code null}
* (use {@linkplain Filter#INCLUDE} instead)
*
* @return features retrieved by the {@code Filter}
*
* @throws IOException if the underlying data source cannot be accessed.
*
* @see Filter
*/
FeatureCollection<T, F> getFeatures(Filter filter) throws IOException;
/**
* Retrieves features, in the form of a {@code FeatureCollection}, based
* on a {@code Query}.
*
* @param query DataAccess query for requested information, such as typeName,
* maxFeatures and filter.
*
* @return features retrieved by the {@code Query}
*
* @throws IOException if the underlying data source cannot be accessed.
*
* @see Query
*/
FeatureCollection<T, F> getFeatures(Query query) throws IOException;
/**
* Retrieves all features in the form of a {@code FeatureCollection}.
* <p>
* The following statements are equivalent:
* <pre><code>
* featureSource.getFeatures();
* featureSource.getFeatures(Filter.INCLUDE);
* featureSource.getFeatures(Query.ALL);
* </code></pre>
*
* @return features retrieved by the {@code Query}
*
* @throws IOException if the underlying data source cannot be accessed.
*/
FeatureCollection<T, F> getFeatures() throws IOException;
/**
* Retrieves the schema (feature type) that will apply to features retrieved
* from this {@code FeatureSource}.
* <p>
* 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.
*
* @return the schema that will apply to features retrieved from this
* {@code FeatureSource}
*/
T getSchema();
/**
* Get the spatial bounds of the feature data. This is equivalent
* to calling <code>getBounds(Query.ALL)</code>.
* <p>
* 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 <code>getFeatures().getBounds()</code>
* instead.
*
* @return The bounding envelope of the feature data; or {@code null}
* if the bounds are unknown or too costly to calculate.
*
* @throws IOException on any errors calculating the bounds
*/
ReferencedEnvelope getBounds() throws IOException;
/**
* Get the spatial bounds of the features that would be returned by
* the given {@code Query}.
* <p>
* 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 <code>getFeatures(query).getBounds()</code>
* instead.
*
* @param query the query to select features
*
* @return The bounding envelope of the feature data; or {@code null}
* if the bounds are unknown or too costly to calculate.
*
* @throws IOException on any errors calculating the bounds
*/
ReferencedEnvelope getBounds(Query query) throws IOException;
/**
* Gets the number of the features that would be returned by the given
* {@code Query}, taking into account any settings for max features and
* start index set on the {@code Query}.
* <p>
* It is possible that this method will return {@code -1} if the calculation
* of number of features is judged to be too costly by the implementing class.
* In this case, you might call <code>getFeatures(query).getBounds()</code>
* instead.
*
* @param query the query to select features
*
* @return the numer of features that would be returned by the {@code Query};
* or {@code -1} if this cannot be calculated.
*
* @throws IOException if there are errors getting the count
*/
int getCount(Query query) throws IOException;
/**
* Returns the set of hints that this {@code FeatureSource} supports via {@code Query} requests.
* <p>
* Note: the existence of a specific hint does not guarantee that it will always be honored by
* the implementing class.
*
* @see Hints#FEATURE_DETACHED
* @see Hints#JTS_GEOMETRY_FACTORY
* @see Hints#JTS_COORDINATE_SEQUENCE_FACTORY
* @see Hints#JTS_PRECISION_MODEL
* @see Hints#JTS_SRID
* @see Hints#GEOMETRY_DISTANCE
* @see Hints#FEATURE_2D
* @return a set of {@code RenderingHints#Key} objects; may be empty but never {@code null}
*/
public Set<RenderingHints.Key> getSupportedHints();
// FeatureReader getFeatureReader( Query query ); // ask justin for proposal
}