org.geotools.data
Class FilteringFeatureReader

java.lang.Object
  extended byorg.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


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