/**
* 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;
}
/**
* This method lists all the entities inserted in datastore. It uses HTTP GET method and paging
* support.
*
* @return A CollectionResponse class containing the list of all entities persisted and a cursor
* to the next page.
*/
@SuppressWarnings({"unchecked", "unused"})
@ApiMethod(name = "listUser")
public CollectionResponse<User> listUser(
@Nullable @Named("cursor") String cursorString, @Nullable @Named("limit") Integer limit) {
PersistenceManager mgr = null;
Cursor cursor = null;
List<User> execute = null;
try {
mgr = getPersistenceManager();
Query query = mgr.newQuery(User.class);
if (cursorString != null && cursorString != "") {
cursor = Cursor.fromWebSafeString(cursorString);
HashMap<String, Object> extensionMap = new HashMap<String, Object>();
extensionMap.put(JDOCursorHelper.CURSOR_EXTENSION, cursor);
query.setExtensions(extensionMap);
}
if (limit != null) {
query.setRange(0, limit);
}
execute = (List<User>) query.execute();
cursor = JDOCursorHelper.getCursor(execute);
if (cursor != null) cursorString = cursor.toWebSafeString();
// Tight loop for fetching all entities from datastore and accomodate
// for lazy fetch.
for (User obj : execute) ;
} finally {
mgr.close();
}
return CollectionResponse.<User>builder()
.setItems(execute)
.setNextPageToken(cursorString)
.build();
}
