/**
* Demonstrates how to use the cursor to be able to pass over an complete set of data
*
* @param pm Persistence manager instance to use - let open at the end to allow possible object
* updates later
* @param cursorString Representation of a cursor, to be used to get the next set of data to
* process
* @param range Number of data to process at this particular stage
* @param defaultSource Value to apply to any Demand instance without a default value
* @return New representation of the cursor, ready for a next process call
*/
@SuppressWarnings("unchecked")
public static String updateSource(
PersistenceManager pm, String cursorString, int range, Source defaultSource) {
Query query = null;
try {
query = pm.newQuery(Demand.class);
if (cursorString != null) {
Map<String, Object> extensionMap = new HashMap<String, Object>();
extensionMap.put(JDOCursorHelper.CURSOR_EXTENSION, Cursor.fromWebSafeString(cursorString));
query.setExtensions(extensionMap);
}
query.setRange(0, range);
List<Demand> results = (List<Demand>) query.execute();
if (results.iterator().hasNext()) {
for (Demand demand : results) {
// Initialize the new field if necessary. By checking first that the field is null, we
// allow this migration to be safely run multiple times.
if (demand.getSource() == null) {
demand.setSource(defaultSource);
pm.makePersistent(demand);
}
}
cursorString = JDOCursorHelper.getCursor(results).toWebSafeString();
} else {
// no results
cursorString = null;
}
} finally {
query.closeAll();
}
return cursorString;
}
