content: /**
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 backtype.storm.topology;
  
  import backtype.storm.state.State;
  
  /**
   * Common methods for stateful components in the topology.
   *
   * A stateful component is one that has state (e.g. the result of some computation in a bolt)
   * and wants the framework to manage its state.
   */
  public interface IStatefulComponent<T extends State> extends IComponent {
      /**
       * This method is invoked by the framework with the previously
       * saved state of the component. This is invoked after prepare but before
       * the component starts processing tuples.
       *
       * @param state the previously saved state of the component.
       */
      void initState(T state);
  
      /**
       * This is a hook for the component to perform some actions just before the
       * framework commits its state.
       */
      void preCommit(long txid);
  
      /**
       * This is a hook for the component to perform some actions just before the
       * framework prepares its state.
       */
      void prePrepare(long txid);
  
      /**
       * This is a hook for the component to perform some actions just before the
       * framework rolls back the prepared state.
       */
      void preRollback();
  }
  