org.geotools.data

Interface FeatureReader<T extends FeatureType,F extends Feature>

All Superinterfaces:

AutoCloseable, Closeable

All Known Subinterfaces:

DelegatingFeatureReader<T,F>, SimpleFeatureReader

All Known Implementing Classes:

ArcSDEFeatureReader, CollectionFeatureReader, DefaultFeatureReader, DelegateFeatureReader, DelegateSimpleFeatureReader, DiffFeatureReader, EmptyFeatureReader, EmptySimpleFeatureReader, FCBuffer, FIDFeatureReader, FilteringFeatureReader, FilteringSimpleFeatureReader, ForceCoordinateSystemFeatureReader, JDBCClosingFeatureReader, JDBCFeatureReader, JDBCInsertFeatureWriter, JDBCJoiningFeatureReader, JDBCJoiningFilteringFeatureReader, JDBCUpdateFeatureWriter, JDBCUpdateInsertFeatureWriter, MaxFeatureReader, MemoryFeatureReader, MongoFeatureReader, PreGeneralizedFeatureReader, PropertyFeatureReader, ReprojectFeatureReader, ReTypeFeatureReader, SortedFeatureReader

public interface FeatureReader<T extends FeatureType,F extends Feature>
extends Closeable

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.

Author:

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

Method Summary

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

Method Detail

getFeatureType

T getFeatureType()

Return the FeatureType this reader has been configured to create.

Returns:

the FeatureType of the Features this FeatureReader will create.

next

F next()
throws IOException,
       IllegalArgumentException,
       NoSuchElementException

Reads the next Feature in the FeatureReader.

Returns:

The next feature in the reader.

Throws:

IOException - If an error occurs reading the Feature.

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

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

IllegalArgumentException

hasNext

boolean hasNext()
         throws 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:

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

close

void close()
    throws IOException

Release the underlying resources associated with this stream.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException - if an I/O error occurs