storm-client/src/jvm/org/apache/storm/state/InMemoryKeyValueStateProvider.java

/**
 * 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 org.apache.storm.state;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.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<String, Object> topoConf, 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;
    }
}