storm-client/src/jvm/org/apache/storm/state/KeyValueState.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;

/**
 * A state that supports key-value mappings.
 */
public interface KeyValueState<K, V> extends State, Iterable<Map.Entry<K, V>> {
    /**
     * Maps the value with the key.
     *
     * @param key   the key
     * @param value the value
     */
    void put(K key, V value);

    /**
     * Returns the value mapped to the key.
     *
     * @param key the key
     * @return the value or null if no mapping is found
     */
    V get(K key);

    /**
     * Returns the value mapped to the key or defaultValue if no mapping is found.
     *
     * @param key          the key
     * @param defaultValue the value to return if no mapping is found
     * @return the value or defaultValue if no mapping is found
     */
    V get(K key, V defaultValue);

    /**
     * Deletes the value mapped to the key, if there is any.
     *
     * @param key the key
     */
    V delete(K key);
}