org.geotools.data
Interface FeatureReader

All Known Implementing Classes:

CollectionFeatureReader, DefaultFeatureReader, DelegateFeatureReader, DiffFeatureReader, EmptyFeatureReader, FCBuffer, FIDFeatureReader, FilteringFeatureReader, ForceCoordinateSystemFeatureReader, JDBCFeatureReader, MaxFeatureReader, PropertyFeatureReader, ReprojectFeatureReader, ReTypeFeatureReader, TigerFeatureReader, VPFFeatureReader, VPFFileFeatureReader

public interface FeatureReader

The low-level interface for reading Features. Will use the underlying AttributeReader and the given FeatureType to create new Features.

Typical use is as follows:

   FeatureReader reader = null;
   try{
      for( reader = data.getFeatureReader( filter ); reader.hasNext(); ){
          f = reader.next();
          ...
      }
   }
   catch (IOException problem){
      ...
   }
   finally {
      if( reader != null ){
          try {
             reader.close();
          }
          catch( IOException eek){
          }
      }
   } 
 

Questions and Suggestions

• Q: Should FeatureReader provide access to the AttributeReaders it uses?
  A: No, it looks like we will make a lazy Feature in order to cleanly allow for lazy parsing of attribtues.
• Q:FeatureReader has a close method, but no open method?
  A: This is by design allowing FeatureReader to encapsulate its InputStream or Rowset). Please assume that FeatureReaders are a single use proposition.
• Q: All that exception handling is a pain! A: Yes it is, we have constructed semi-normal Java iterators to cut down on the pain. But you *do* still have to close 'em - this is IO after all.
• Q: Can we include skip(int) - SeanG A: The order of the contents is not "known" or predicatable to the end user, so skip( int ) would be useless. For random access (a higher order of abstraction then FeatureReader) please look at FeatureList.

Version:

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

Author:

Ian Schneider, Sean Geoghegan, Defence Science and Technology Organisation.

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 whether this FeatureReader has another Feature.
Feature	next() Reads the next Feature in the FeatureReader.

Method Detail

getFeatureType

public FeatureType getFeatureType()

Return the FeatureType this reader has been configured to create.

Returns:

the FeatureType of the Features this FeatureReader will create.

next

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

Reads the next Feature in the FeatureReader.

Returns:

The next feature in the reader.

Throws:

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

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

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

hasNext

public boolean hasNext()
                throws java.io.IOException

Query whether this FeatureReader has another Feature.

Returns:

True if there are more Features to be read. In other words, true if calls to next would return a feature rather than throwing an exception.

Throws:

java.io.IOException - If an error occurs determining if there are more Features.

close

public void close()
           throws java.io.IOException

Release the underlying resources associated with this stream.

Throws:

java.io.IOException - DOCUMENT ME!