org.geotools.data
Interface FeatureWriter

All Known Implementing Classes:

DiffFeatureWriter, EmptyFeatureWriter, FilteringFeatureWriter, IndexedShapefileDataStore.Writer, JDBCFeatureWriter, PropertyFeatureWriter, ShapefileDataStore.Writer

public interface FeatureWriter

Provides the ability to write Features information.

Capabilities:

• Similar API to FeatureReader
• After aquiring a feature using next() you may call remove() or after modification write(). If you do not call one of these two methods before calling hasNext(), or next() for that matter, the feature will be left unmodified.
• This API allows modification, and Filter based modification to be written. Please see AbstractDataStore for examples of implementing common opperations using this API.
• In order to add new Features, FeatureWriters capable of accepting new content allow next() to be called when hasNext() is false to allow new feature creation. These changes

One thing that is really nice about the approach to adding content is that the generation of FID is not left in the users control.

Version:

$Id: FeatureWriter.java 17702 2006-01-23 00:08:55Z desruisseaux $

Author:

Ian Schneider, Jody Garnett, Refractions Research

Method Summary

void	close() Release the underlying resources.
FeatureType	getFeatureType() FeatureType this reader has been configured to create.
boolean	hasNext() Query whether this FeatureWriter has another Feature.
Feature	next() Reads a Feature from the underlying AttributeReader.
void	remove() Removes current Feature, must be called before hasNext.
void	write() Wrties the current Feature, must be called before hasNext.

Method Detail

getFeatureType

public FeatureType getFeatureType()

FeatureType this reader has been configured to create.

Returns:

FeatureType this writer has been configured to create.

next

public Feature next()
             throws java.io.IOException

Reads a Feature from the underlying AttributeReader.

This method may return a Feature even though hasNext() returns false, this allows FeatureWriters to provide an ability to append content.

Returns:

Feature from Query, or newly appended Feature

Throws:

java.io.IOException - DOCUMENT ME!

remove

public void remove()
            throws java.io.IOException

Removes current Feature, must be called before hasNext.

FeatureWriters will need to allow all FeatureSources of the same typeName to issue a FeatureEvent event of type FeatureEvent.FEATURES_REMOVED when this method is called.

If this FeatureWriter is opperating against a Transaction FEATURES_REMOVED events should only be sent to FeatureSources operating on the same Transaction. When Transaction commit() is called other FeatureSources will be informed of the modifications.

When the current Feature has been provided as new content, this method "cancels" the add opperation (and notification needed).

Throws:

java.io.IOException - DOCUMENT ME!

write

public void write()
           throws java.io.IOException

Wrties the current Feature, must be called before hasNext.

FeautreWriters will need to allow FeatureSources of the same typeName to issue a FeatureEvent:

• FeatureEvent.FEATURES_ADDED: when next() has been called with hasNext() equal to false.
• FeatureEvent.FEATURES_MODIFIED: when next has been called with hasNext() equal to true and the resulting Feature has indeed been modified.

If this FeatureWriter is opperating against a Transaction the FEATURES_MODIFIED or FEATURES_ADDED events should only be sent to FeatureSources opperating on the same Transaction. When Transaction commit() is called other FeatureSources will be informed of the modifications.

If you have not called write() when you call hasNext() or next(), no modification will occur().

Throws:

java.io.IOException

hasNext

public boolean hasNext()
                throws java.io.IOException

Query whether this FeatureWriter has another Feature.

Please note: it is more efficient to construct your FeatureWriter with a Filer (to skip entries you do not want), than to force the creation of entire Features only to skip over them.

FeatureWriters that support append opperations will allow calls to next, even when haveNext() returns false.

Returns:

true if an additional Feature is available.

Throws:

java.io.IOException - DOCUMENT ME!

close

public void close()
           throws java.io.IOException

Release the underlying resources.

Throws:

java.io.IOException - if there there are problems releasing underlying resources, or possibly if close has been called (up to the implementation).