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.state;
  
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  import backtype.storm.task.TopologyContext;
  
  /**
   * Provides {@link InMemoryKeyValueState}
   */
  public class InMemoryKeyValueStateProvider implements StateProvider {
      private final ConcurrentHashMap<String, State> states = new ConcurrentHashMap<>();
  
      @Override
      public State newState(String namespace, Map stormConf, TopologyContext context) {
          State state = states.get(namespace);
          if (state == null) {
              State newState = new InMemoryKeyValueState<>();
              state = states.putIfAbsent(namespace, newState);
              if (state == null) {
                  state = newState;
              }
          }
          return state;
      }
  }
  