Package org.geotools.data

Class FilteringFeatureReader<T extends FeatureType,F extends Feature>

Object

FilteringFeatureReader<T,F>

All Implemented Interfaces:

Closeable, AutoCloseable, DelegatingFeatureReader<T,F>, FeatureReader<T,F>

Direct Known Subclasses:

FilteringSimpleFeatureReader

public class FilteringFeatureReader<T extends FeatureType,F extends Feature>
extends Object
implements DelegatingFeatureReader<T,F>

Basic support for a FeatureReader that does filtering. I think that filtering should perhaps be done in the AttributeReader. I'm still having a bit of trouble with the split between attributeReader and featureReader as to where the hooks for advanced processing like filtering should take place. See my note on hasNext(), as the method is currently broken and there are more optimizations that could take place if we had a FilteringAttributeReader. So this class may go, but I thought I'd put the ideas into code.

Jody here - changed hasNext() to peek as required.

Author:

Chris Holmes

Field Summary

Fields

Modifier and Type	Field	Description
protected FeatureReader<T,F>	featureReader
protected Filter	filter
protected F	next

Constructor Summary

Constructors

Constructor	Description
FilteringFeatureReader(FeatureReader<T,F> featureReader, Filter filter)	Creates a new instance of AbstractFeatureReader

Method Summary

Modifier and Type	Method	Description
void	close()	Release the underlying resources associated with this stream.
FeatureReader<T,F>	getDelegate()
T	getFeatureType()	Return the FeatureType this reader has been configured to create.
boolean	hasNext()	Query for additional content.
F	next()	Reads the next Feature in the FeatureReader.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

featureReader

protected final FeatureReader<T extends FeatureType,F extends Feature> featureReader

filter

protected final Filter filter

next

protected F extends Feature next

Constructor Detail

FilteringFeatureReader

public FilteringFeatureReader(FeatureReader<T,F> featureReader,
                              Filter filter)

Creates a new instance of AbstractFeatureReader

Please don't call this method with Filter.INCLUDE or Filter.EXCLUDE (consider not filtering and EmptyFeatureReader instead)

Parameters:

featureReader - FeatureReader being filtered

filter - Filter used to limit the results of featureReader

Method Detail

getDelegate

public FeatureReader<T,F> getDelegate()

Specified by:

getDelegate in interface DelegatingFeatureReader<T extends FeatureType,F extends Feature>

Returns:

THe delegate reader.

next

public F next()
       throws IOException,
              IllegalAttributeException,
              NoSuchElementException

Description copied from interface: FeatureReader

Reads the next Feature in the FeatureReader.

Specified by:

next in interface FeatureReader<T extends FeatureType,F extends Feature>

Returns:

The next feature in the reader.

Throws:

IOException - If an error occurs reading the Feature.

NoSuchElementException - If there are no more Features in the Reader.

IllegalAttributeException

close

public void close()
           throws IOException

Description copied from interface: FeatureReader

Release the underlying resources associated with this stream.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface FeatureReader<T extends FeatureType,F extends Feature>

Throws:

IOException - if an I/O error occurs

getFeatureType

public T getFeatureType()

Description copied from interface: FeatureReader

Return the FeatureType this reader has been configured to create.

Specified by:

getFeatureType in interface FeatureReader<T extends FeatureType,F extends Feature>

Returns:

the FeatureType of the Features this FeatureReader will create.

hasNext

public boolean hasNext()
                throws IOException

Query for additional content.

This class will peek ahead to see if there is additional content.

Chris has pointed out that we could make use of AttributeReader based filtering:
"Also doing things in the Attribute Reader would allow us to do the smart filtering, only looking at the attributes needed for comparison, whereas doing filtering here means we have to create an entire feature each time."

Specified by:

hasNext in interface FeatureReader<T extends FeatureType,F extends Feature>

Returns:

true if we have additional content

Throws:

IOException - If the reader we are filtering encounters a problem

DataSourceException - See IOException