ObservableClient.java

/*
 * Copyright (c) 2015 Spotify AB
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */


package com.spotify.folsom;

/**
 * Implementations of this interface has a notion of connectedness to a remote
 * and the ability to notify listeners of connection state changes.
 */
public interface ObservableClient {
  /**
   * Register for connection change events. This should trigger at least once for every
   * connection change. You should immediately get an initial callback, so that if you
   * are creating a ListenableFuture looking for a connection state that has already
   * been reached it will return immediately.
   *
   * @param listener the listener to notify of connection changes
   */
  void registerForConnectionChanges(ConnectionChangeListener listener);

  /**
   * Unregister the provided listener so that it no longer receives connection change
   * callbacks.
   * @param listener the listener to unregister.
   */
  void unregisterForConnectionChanges(ConnectionChangeListener listener);

  /**
   * Is the client connected to a server?
   * @return true if the client is connected
   */
  boolean isConnected();
}