org.geotools.data
Class FilteringFeatureReader

java.lang.Object
  org.geotools.data.FilteringFeatureReader

All Implemented Interfaces:

FeatureReader

public class FilteringFeatureReader

extends java.lang.Object

implements FeatureReader

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.

Version:

$Id: FilteringFeatureReader.java 17701 2006-01-23 00:00:51Z desruisseaux $

Author:

Chris Holmes

Field Summary

protected FeatureReader	featureReader
protected Filter	filter
protected Feature	next

Constructor Summary

FilteringFeatureReader(FeatureReader featureReader, Filter filter)
Creates a new instance of AbstractFeatureReader Please don't call this method with Filter.NONE or Filter.ALL (consider not filtering and EmptyFeatureReader instead)

Method Summary

void	close() Release the underlying resources associated with this stream.
FeatureType	getFeatureType() Return the FeatureType this reader has been configured to create.
boolean	hasNext() Query for additional content.
Feature	next() Reads the next Feature in the FeatureReader.

Methods inherited from class java.lang.Object

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

Field Detail

featureReader

protected final FeatureReader featureReader

filter

protected final Filter filter

next

protected Feature next

Constructor Detail

FilteringFeatureReader

public FilteringFeatureReader(FeatureReader featureReader,
                              Filter filter)

Creates a new instance of AbstractFeatureReader

Please don't call this method with Filter.NONE or Filter.ALL (consider not filtering and EmptyFeatureReader instead)

Parameters:

featureReader - FeatureReader being filtered

filter - Filter used to limit the results of featureReader

Method Detail

next

public Feature next()
             throws java.io.IOException,
                    IllegalAttributeException,
                    java.util.NoSuchElementException

Description copied from interface: FeatureReader

Reads the next Feature in the FeatureReader.

Specified by:

next in interface FeatureReader

Returns:

The next feature in the reader.

Throws:

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

IllegalAttributeException - If the attributes read do not comply with the FeatureType.

java.io.IOException - If an error occurs reading the Feature.

close

public void close()
           throws java.io.IOException

Description copied from interface: FeatureReader

Release the underlying resources associated with this stream.

Specified by:

close in interface FeatureReader

Throws:

java.io.IOException - DOCUMENT ME!

getFeatureType

public FeatureType getFeatureType()

Description copied from interface: FeatureReader

Return the FeatureType this reader has been configured to create.

Specified by:

getFeatureType in interface FeatureReader

Returns:

the FeatureType of the Features this FeatureReader will create.

hasNext

public boolean hasNext()
                throws java.io.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

Returns:

true if we have additional content

Throws:

java.io.IOException - If the reader we are filtering encounters a problem

DataSourceException - See IOException