org.apache.kafka.streams.processor.ConnectedStoreProvider Maven / Gradle / Ivy
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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,
* 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.kafka.streams.processor;
import org.apache.kafka.streams.Topology;
import org.apache.kafka.streams.kstream.KStream;
import org.apache.kafka.streams.kstream.Named;
import org.apache.kafka.streams.kstream.TransformerSupplier;
import org.apache.kafka.streams.kstream.ValueTransformerSupplier;
import org.apache.kafka.streams.kstream.ValueTransformerWithKeySupplier;
import org.apache.kafka.streams.state.StoreBuilder;
import java.util.Set;
/**
* Provides a set of {@link StoreBuilder}s that will be automatically added to the topology and connected to the
* associated processor.
*
* Implementing this interface is recommended when the associated processor wants to encapsulate its usage of its state
* stores, rather than exposing them to the user building the topology.
*
* In the event that separate but related processors may want to share the same store, different {@link ConnectedStoreProvider}s
* may provide the same instance of {@link StoreBuilder}, as shown below.
*
{@code
* class StateSharingProcessors {
* StoreBuilder> storeBuilder =
* Stores.keyValueStoreBuilder(Stores.persistentKeyValueStore("myStore"), Serdes.String(), Serdes.String());
*
* class SupplierA implements ProcessorSupplier {
* Processor get() {
* return new Processor() {
* private StateStore store;
*
* void init(ProcessorContext context) {
* this.store = context.getStateStore("myStore");
* }
*
* void process(String key, Integer value) {
* // can access this.store
* }
*
* void close() {
* // can access this.store
* }
* }
* }
*
* Set> stores() {
* return Collections.singleton(storeBuilder);
* }
* }
*
* class SupplierB implements ProcessorSupplier {
* Processor get() {
* return new Processor() {
* private StateStore store;
*
* void init(ProcessorContext context) {
* this.store = context.getStateStore("myStore");
* }
*
* void process(String key, String value) {
* // can access this.store
* }
*
* void close() {
* // can access this.store
* }
* }
* }
*
* Set> stores() {
* return Collections.singleton(storeBuilder);
* }
* }
* }
* }
*
* @see Topology#addProcessor(String, org.apache.kafka.streams.processor.api.ProcessorSupplier, String...)
* @see KStream#process(org.apache.kafka.streams.processor.api.ProcessorSupplier, String...)
* @see KStream#process(org.apache.kafka.streams.processor.api.ProcessorSupplier, Named, String...)
* @see KStream#transform(TransformerSupplier, String...)
* @see KStream#transform(TransformerSupplier, Named, String...)
* @see KStream#transformValues(ValueTransformerSupplier, String...)
* @see KStream#transformValues(ValueTransformerSupplier, Named, String...)
* @see KStream#transformValues(ValueTransformerWithKeySupplier, String...)
* @see KStream#transformValues(ValueTransformerWithKeySupplier, Named, String...)
* @see KStream#flatTransform(TransformerSupplier, String...)
* @see KStream#flatTransform(TransformerSupplier, Named, String...)
* @see KStream#flatTransformValues(ValueTransformerSupplier, String...)
* @see KStream#flatTransformValues(ValueTransformerSupplier, Named, String...)
* @see KStream#flatTransformValues(ValueTransformerWithKeySupplier, String...)
* @see KStream#flatTransformValues(ValueTransformerWithKeySupplier, Named, String...)
*/
public interface ConnectedStoreProvider {
/**
* @return the state stores to be connected and added, or null if no stores should be automatically connected and added.
*/
default Set> stores() {
return null;
}
}