StateStoreProvider.java example

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/*
 * 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,
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 * See the License for the specific language governing permissions and
 * limitations under the License.
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package org.apache.kafka.streams.state.internals;

import org.apache.kafka.streams.processor.StateStore;
import org.apache.kafka.streams.state.QueryableStoreType;
import org.apache.kafka.streams.state.QueryableStoreTypes;

import java.util.List;

/**
 * Provides access to {@link StateStore}s that have been created
 * as part of the {@link org.apache.kafka.streams.processor.internals.ProcessorTopology}.
 * To get access to custom stores developers should implement {@link QueryableStoreType}.
 * @see QueryableStoreTypes
 */
public interface StateStoreProvider {

    /**
     * Find instances of StateStore that are accepted by {@link QueryableStoreType#accepts} and
     * have the provided storeName.
     *
     * @param storeName             name of the store
     * @param queryableStoreType    filter stores based on this queryableStoreType
     * @param <T>                   The type of the Store
     * @return  List of the instances of the store in this topology. Empty List if not found
     */
    <T> List<T> stores(String storeName, QueryableStoreType<T> queryableStoreType);
}