Java Code Examples for com.google.appengine.api.datastore.Cursor#fromWebSafeString()

@Test
public void testStartEndCursor() {
    int limit = total / testDat.length;
    Query query = new Query(kindName, rootKey);
    query.addSort("name", Query.SortDirection.ASCENDING);
    FetchOptions fetchOption = FetchOptions.Builder.withLimit(limit);
    // fetch 1st page and get cursor1
    QueryResultList<Entity> nextBatch = service.prepare(query)
        .asQueryResultList(fetchOption);
    Cursor cursor1 = Cursor.fromWebSafeString(nextBatch.getCursor().toWebSafeString());
    // fetch 2nd page and get cursor2
    nextBatch = service.prepare(query).asQueryResultList(fetchOption.startCursor(cursor1));
    Cursor cursor2 = Cursor.fromWebSafeString(nextBatch.getCursor().toWebSafeString());
    // cursor1 as start and cursor2 as end and 15 in limit -- -- should return 2nd page.
    checkPage(query, cursor1, cursor2, limit, limit, testDat[1], testDat[1]);
    // cursor1 as start and cursor2 as end and 30 in limit -- should return 2nd page.
    checkPage(query, cursor1, cursor2, 2 * limit, limit, testDat[1], testDat[1]);
    // cursor2 as start and cursor1 as end and 15 in limit -- should not return any.
    checkPage(query, cursor2, cursor1, limit, 0, null, null);
}
 

@Test
public void testFilter() {
    int onePage = 5;
    String filterData = "ff";
    Query query = new Query(kindName, rootKey);
    query.setFilter(new FilterPredicate("name", Query.FilterOperator.EQUAL, filterData));
    // fetch first page
    Cursor cursor = checkPage(query, null, null, onePage, onePage, filterData, filterData);
    Cursor decodedCursor = Cursor.fromWebSafeString(cursor.toWebSafeString());
    // fetch next page
    checkPage(query, decodedCursor, null, onePage, onePage, filterData, filterData);
}
 

@Test
public void testEndFetch() {
    int onePage = total - 30;
    Query query = new Query(kindName, rootKey);
    // fetch first page
    Cursor cursor = checkPage(query, null, null, onePage, onePage, null, null);
    Cursor decodedCursor = Cursor.fromWebSafeString(cursor.toWebSafeString());
    // fetch next page,   get remaining after 1st page.
    checkPage(query, decodedCursor, null, onePage, total - onePage, null, null);
}
 

@Test
public void testEndCursor() {
    int limit = total / testDat.length;
    Query query = new Query(kindName, rootKey);
    query.addSort("name", Query.SortDirection.ASCENDING);
    // fetch 1st page
    Cursor cursor = checkPage(query, null, null, limit, limit, testDat[0], testDat[0]);
    Cursor decodedCursor = Cursor.fromWebSafeString(cursor.toWebSafeString());
    // fetch 1st page again since using decodedCursor as end cursor
    checkPage(query, null, decodedCursor, limit, limit, testDat[0], testDat[0]);
}
 

/**
 * 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 = "listOffer")
public CollectionResponse<Offer> listOffer(
    @Nullable @Named("cursor") String cursorString, @Nullable @Named("limit") Integer limit) {

  EntityManager mgr = null;
  Cursor cursor = null;
  List<Offer> execute = null;

  try {
    mgr = getEntityManager();
    Query query = mgr.createQuery("select from Offer as Offer");
    if (cursorString != null && cursorString != "") {
      cursor = Cursor.fromWebSafeString(cursorString);
      query.setHint(JPACursorHelper.CURSOR_HINT, cursor);
    }

    if (limit != null) {
      query.setFirstResult(0);
      query.setMaxResults(limit);
    }

    execute = (List<Offer>) query.getResultList();
    cursor = JPACursorHelper.getCursor(execute);
    if (cursor != null) cursorString = cursor.toWebSafeString();

    // Tight loop for fetching all entities from datastore and accomodate
    // for lazy fetch.
    for (Offer obj : execute);
  } finally {
    mgr.close();
  }

  return CollectionResponse.<Offer>builder()
      .setItems(execute).setNextPageToken(cursorString).build();
}
 

/**
 * 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 = "listRecommendation")
public CollectionResponse<Recommendation> listRecommendation(
    @Nullable @Named("cursor") String cursorString, @Nullable @Named("limit") Integer limit) {

  EntityManager mgr = null;
  Cursor cursor = null;
  List<Recommendation> execute = null;

  try {
    mgr = getEntityManager();
    Query query = mgr.createQuery("select from Recommendation as Recommendation");
    if (cursorString != null && cursorString != "") {
      cursor = Cursor.fromWebSafeString(cursorString);
      query.setHint(JPACursorHelper.CURSOR_HINT, cursor);
    }

    if (limit != null) {
      query.setFirstResult(0);
      query.setMaxResults(limit);
    }

    execute = (List<Recommendation>) query.getResultList();
    cursor = JPACursorHelper.getCursor(execute);
    if (cursor != null) cursorString = cursor.toWebSafeString();

    // Tight loop for fetching all entities from datastore and accomodate
    // for lazy fetch.
    for (Recommendation obj : execute);
  } finally {
    mgr.close();
  }

  return CollectionResponse.<Recommendation>builder()
      .setItems(execute).setNextPageToken(cursorString).build();
}
 

/**
 * 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 = "listCheckIn")
public CollectionResponse<CheckIn> listCheckIn(
    @Nullable @Named("cursor") String cursorString, @Nullable @Named("limit") Integer limit) {

  EntityManager mgr = null;
  Cursor cursor = null;
  List<CheckIn> execute = null;

  try {
    mgr = getEntityManager();
    Query query = mgr.createQuery("select from CheckIn as CheckIn");
    if (cursorString != null && cursorString != "") {
      cursor = Cursor.fromWebSafeString(cursorString);
      query.setHint(JPACursorHelper.CURSOR_HINT, cursor);
    }

    if (limit != null) {
      query.setFirstResult(0);
      query.setMaxResults(limit);
    }

    execute = (List<CheckIn>) query.getResultList();
    cursor = JPACursorHelper.getCursor(execute);
    if (cursor != null) cursorString = cursor.toWebSafeString();

    // Tight loop for fetching all entities from datastore and accomodate
    // for lazy fetch.
    for (CheckIn obj : execute);
  } finally {
    mgr.close();
  }

  return CollectionResponse.<CheckIn>builder()
      .setItems(execute).setNextPageToken(cursorString).build();
}
 

/**
 * 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 = "listDeviceInfo")
public CollectionResponse<DeviceInfo> listDeviceInfo(
    @Nullable @Named("cursor") String cursorString, @Nullable @Named("limit") Integer limit) {

  EntityManager mgr = null;
  Cursor cursor = null;
  List<DeviceInfo> execute = null;

  try {
    mgr = getEntityManager();
    Query query = mgr.createQuery("select from DeviceInfo as DeviceInfo");
    if (cursorString != null && cursorString != "") {
      cursor = Cursor.fromWebSafeString(cursorString);
      query.setHint(JPACursorHelper.CURSOR_HINT, cursor);
    }

    if (limit != null) {
      query.setFirstResult(0);
      query.setMaxResults(limit);
    }

    execute = (List<DeviceInfo>) query.getResultList();
    cursor = JPACursorHelper.getCursor(execute);
    if (cursor != null) cursorString = cursor.toWebSafeString();

    // Tight loop for fetching all entities from datastore and accomodate
    // for lazy fetch.
    for (DeviceInfo obj : execute);
  } finally {
    mgr.close();
  }

  return CollectionResponse.<DeviceInfo>builder()
      .setItems(execute).setNextPageToken(cursorString).build();
}
 

/**
 * 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 = "listPlace")
public CollectionResponse<Place> listPlace(
    @Nullable @Named("cursor") String cursorString, @Nullable @Named("limit") Integer limit) {

  EntityManager mgr = null;
  Cursor cursor = null;
  List<Place> execute = null;

  try {
    mgr = getEntityManager();
    Query query = mgr.createQuery("select from Place as Place");
    if (cursorString != null && cursorString != "") {
      cursor = Cursor.fromWebSafeString(cursorString);
      query.setHint(JPACursorHelper.CURSOR_HINT, cursor);
    }

    if (limit != null) {
      query.setFirstResult(0);
      query.setMaxResults(limit);
    }

    execute = (List<Place>) query.getResultList();
    cursor = JPACursorHelper.getCursor(execute);
    if (cursor != null) cursorString = cursor.toWebSafeString();

    // Tight loop for fetching all entities from datastore and accomodate
    // for lazy fetch.
    for (Place obj : execute);
  } finally {
    mgr.close();
  }

  return CollectionResponse.<Place>builder()
      .setItems(execute).setNextPageToken(cursorString).build();
}
 

/**
 * This function returns a list of messages starting with the newest message
 * first and in descending order from there
 * 
 * @param cursorString 
 *          for paging, empty for the first request, subsequent requests can
 *          use the returned information from an earlier request to fill this
 *          parameter
 * @param limit
 *          number of results returned for this query
 * @return
 *          A collection of MessageData items
 */
@SuppressWarnings({ "unchecked", "unused" })
@ApiMethod(name = "listMessages")
public CollectionResponse<MessageData> listMessages(
    @Nullable @Named("cursor") String cursorString,
    @Nullable @Named("limit") Integer limit) {

  EntityManager mgr = null;  
  Cursor cursor = null;
  List<MessageData> execute = null;
  
  try {
    mgr = getEntityManager();
    // query for messages, newest message first
    Query query = mgr
        .createQuery("select from MessageData as MessageData order by timestamp desc");
    if (cursorString != null && cursorString != "") {
      cursor = Cursor.fromWebSafeString(cursorString);
      query.setHint(JPACursorHelper.CURSOR_HINT, cursor);
    }

    if (limit != null) {
      query.setFirstResult(0);
      query.setMaxResults(limit);
    }

    execute = (List<MessageData>) query.getResultList();
    cursor = JPACursorHelper.getCursor(execute);
    if (cursor != null)
      cursorString = cursor.toWebSafeString();

    // Tight loop for fetching all entities from datastore and accomodate
    // for lazy fetch.
    for (MessageData obj : execute) {
      ;
    }
  } finally {
    mgr.close();
  }

  return CollectionResponse.<MessageData> builder().setItems(execute)
      .setNextPageToken(cursorString).build();
}
 

private void preprocessBatchOfDevices(String alertMessage, String cursorString) {
  EntityManager mgr = null;
  Cursor cursor = null;

  try {
    mgr = getEntityManager();

    // Retrieve entities (and not just deviceToken property) in order to paginate using cursor
    Query query = mgr.createQuery("select from DeviceRegistration as DeviceRegistration");
    if (cursorString != null && cursorString != "") {
      cursor = Cursor.fromWebSafeString(cursorString);
      query.setHint(JPACursorHelper.CURSOR_HINT, cursor);
    }

    query.setMaxResults(BATCH_SIZE);

    @SuppressWarnings("unchecked")
    List<DeviceRegistration> deviceRegistrations = query.getResultList();
    cursor = JPACursorHelper.getCursor(deviceRegistrations);
    if (cursor != null) {
      cursorString = cursor.toWebSafeString();
    }

    List<String> deviceTokens = new ArrayList<String>();
    for (DeviceRegistration deviceRegistartion : deviceRegistrations) {
      deviceTokens.add(deviceRegistartion.getDeviceToken());
    }

    if (deviceTokens.isEmpty()) {
      // no more matching device tokens matching this query.
      return;
    }

    mgr.getTransaction().begin();

    try {
      PushNotificationUtility.enqueuePushAlert(alertMessage, deviceTokens);

      if (deviceRegistrations.size() == BATCH_SIZE) {
        PushNotificationUtility.continueEnqueueingPushAlertToAllDevices(
            alertMessage, cursorString);
      }

      mgr.getTransaction().commit();
    } catch (RuntimeException e) {
      if (mgr.getTransaction().isActive()) {
        mgr.getTransaction().rollback();
      }
      throw e;
    }

  } finally {
    mgr.close();
  }
}