JDBCDataStore iterators violate the FeatureIterator contract
------------------------------------------------------------
Key: GEOT-3190
URL: http://jira.codehaus.org/browse/GEOT-3190
Project: GeoTools
Issue Type: Bug
Components: data jdbc-ng
Affects Versions: 2.7-M1
Reporter: Andrea Aime
Assignee: Justin Deoliveira
Calling store.getFeatureSource().features().features().next() throws the
following:
{code}
java.lang.IllegalStateException: Must call hasNext before calling next
at
org.geotools.jdbc.JDBCFeatureReader.ensureNext(JDBCFeatureReader.java:240)
{code}
Now, looking at the FeatureIterator interface there I don't see any contract
asking to call hasNext() before next():
{code}
/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2002-2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.feature;
import org.opengis.feature.Feature;
/**
* A drop in replacement for Iterator<Feature> supporting a close method.
*
* @author Ian Schneider
* @source $URL$
*/
public interface FeatureIterator<F extends Feature> {
/**
* Does another Feature exist in this Iteration.
* <p>
* Iterator defin: Returns true if the iteration has more elements. (In
other words, returns true if next would return an element rather than throwing
an exception.)
* </p>
* @return true if more Features exist, false otherwise.
*/
public boolean hasNext();
/**
* Get the next Feature in this iteration.
*
* @return The next Feature
*
* @throws java.util.NoSuchElementException If no more Features exist.
*/
public F next() throws java.util.NoSuchElementException;
/**
* Required so SimpleFeatureCollection classes can implement close(
FeatureIterator<SimpleFeature> ).
*/
public void close();
}
{code}
And then looking at FeatureReader, same, I see no trace of that contract:
{code}
/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.data;
import java.io.IOException;
import java.util.NoSuchElementException;
import org.opengis.feature.Feature;
import org.opengis.feature.type.FeatureType;
/**
* The low-level interface for reading Features. Will use the underlying
* AttributeReader and the given FeatureType to create new Features.
*
* <p>
* Typical use is as follows:
* <pre><code>
* 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){
* }
* }
* }
* </code></pre>
*
* <h2>Questions and Suggestions</h2>
* <ul>
* <li>Q: Should FeatureReader provide access to the AttributeReaders it uses?
* <br>A:
* No, it looks like we will make a lazy Feature in order to cleanly
* allow for lazy parsing of attribtues.
* </li>
* <li>Q:FeatureReader has a close method, but no open method?
* <br>A: This is by design allowing FeatureReader to encapsulate its
InputStream
* or Rowset). Please assume that FeatureReaders are a single use
proposition.
* </li>
* <li>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.
* </li>
* <li>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.
* </li>
* </ul>
* </p>
*
* @author Ian Schneider
* @author Sean Geoghegan, Defence Science and Technology Organisation.
* @source $URL$
* @version $Id$
*/
public interface FeatureReader<T extends FeatureType, F extends Feature> {
/**
* Return the FeatureType this reader has been configured to create.
*
* @return the FeatureType of the Features this FeatureReader will create.
*/
T getFeatureType();
/**
* Reads the next Feature in the FeatureReader.
*
* @return The next feature in the reader.
*
* @throws IOException If an error occurs reading the Feature.
* @throws IllegalAttributeException If the attributes read do not comply
* with the FeatureType.
* @throws NoSuchElementException If there are no more Features in the
* Reader.
*/
F next() throws IOException, IllegalArgumentException,
NoSuchElementException;
/**
* Query whether this FeatureReader has another Feature.
*
* @return 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.
*/
boolean hasNext() throws IOException;
/**
* Release the underlying resources associated with this stream.
*
* @throws IOException DOCUMENT ME!
*/
void close() throws IOException;
}
{code}
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