Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.wake.rx;
020
021/**
022 * Provides a mechanism for receiving push-based notifications. Implicit
023 * contract: zero or more calls of onNext, if a sequence terminates, it is
024 * terminated by onError or onCompleted in T
025 *
026 * @param <T>
027 */
028public interface Observer<T> {
029
030  /**
031   * Provides the observer with new data.
032   *
033   * @param value
034   */
035  void onNext(final T value);
036
037  /**
038   * Notifies the observer that the provider has experienced an error
039   * condition.
040   *
041   * @param error
042   */
043  void onError(final Exception error);
044
045  /**
046   * Notifies the observer that the provider has finished sending push-based
047   * notifications.
048   */
049  void onCompleted();
050}