// This software is released into the Public Domain. See copying.txt for details.
package org.openstreetmap.osmosis.core.store;
import java.util.NoSuchElementException;
import org.openstreetmap.osmosis.core.lifecycle.ReleasableIterator;
/**
* Wraps an underlying iterator implementation so that all data is read from the
* underlying reader and written to a temporary file before being returned. This
* allows underlying resources such as database connections to be closed sooner
* than otherwise possible. This object will own the wrapped source iterator and
* release it along with all other resources.
*
* @author Brett Henderson
* @param <T>
* The type of entity to retrieved.
*/
public class PersistentIterator<T extends Storeable> implements ReleasableIterator<T> {
private ReleasableIterator<T> sourceIterator;
private SimpleObjectStore<T> store;
private ReleasableIterator<T> storeIterator;
private boolean initialized;
/**
* Creates a new instance.
*
* @param serializationFactory
* The factory defining the object serialisation implementation.
* @param sourceIterator
* The source of data.
* @param storageFilePrefix
* The prefix of the storage file.
* @param useCompression
* If true, the storage file will be compressed.
*/
public PersistentIterator(
ObjectSerializationFactory serializationFactory,
ReleasableIterator<T> sourceIterator,
String storageFilePrefix,
boolean useCompression) {
this.sourceIterator = sourceIterator;
store = new SimpleObjectStore<T>(serializationFactory, storageFilePrefix, useCompression);
initialized = false;
}
private void initialize() {
if (!initialized) {
while (sourceIterator.hasNext()) {
store.add(sourceIterator.next());
}
sourceIterator.close();
sourceIterator = null;
storeIterator = store.iterate();
initialized = true;
}
}
/**
* {@inheritDoc}
*/
public boolean hasNext() {
initialize();
return storeIterator.hasNext();
}
/**
* {@inheritDoc}
*/
public T next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
return storeIterator.next();
}
/**
* {@inheritDoc}
*/
public void close() {
if (storeIterator != null) {
storeIterator.close();
storeIterator = null;
}
store.close();
if (sourceIterator != null) {
sourceIterator.close();
sourceIterator = null;
}
}
/**
* {@inheritDoc}
*/
public void remove() {
throw new UnsupportedOperationException();
}
}