philipnee commented on code in PR #14670: URL: https://github.com/apache/kafka/pull/14670#discussion_r1377933810
########## clients/src/main/java/org/apache/kafka/clients/consumer/internals/ConsumerDelegateCreator.java: ########## @@ -0,0 +1,132 @@ +/* + * 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.clients.consumer.internals; + +import org.apache.kafka.clients.consumer.Consumer; +import org.apache.kafka.clients.consumer.ConsumerConfig; +import org.apache.kafka.clients.consumer.KafkaConsumer; +import org.apache.kafka.common.KafkaException; +import org.apache.kafka.common.serialization.Deserializer; + +import java.util.Map; +import java.util.Properties; +import java.util.function.Supplier; + +/** + * {@code ConsumerDelegateCreator} implements a quasi-factory pattern to allow the caller to remain unaware of the + * underlying {@link Consumer} implementation that is created. This provides the means by which {@link KafkaConsumer} + * can remain the top-level facade for implementations, but allow different implementations to co-exist under + * the covers. + * + * <p/> + * + * The current logic for the {@code ConsumerCreator} inspects the incoming configuration and determines if + * it is using the new KIP-848 consumer protocol or if it should fall back to the existing, legacy group protocol. + * This is based on the presence and value of the {@code group.protocol} configuration value. If the value is present + * and equals {@code consumer}, the {@link AsyncKafkaConsumer} will be returned. Otherwise, the + * {@link LegacyKafkaConsumer} will be returned. + * + * <p/> + * + * This is not to be called by end users and callers should not attempt to determine the underlying implementation + * as this will make such code very brittle. Users of this facility should honor the top-level {@link Consumer} API + * contract as-is. + */ +public class ConsumerDelegateCreator { + + /** + * This is it! This is the core logic. It's extremely rudimentary. + */ + private static boolean useNewConsumer(Map<?, ?> configs) { + Object groupProtocol = configs.get("group.protocol"); + + // Takes care of both the null and type checks. + if (!(groupProtocol instanceof String)) + return false; + + return ((String) groupProtocol).equalsIgnoreCase("consumer"); + } + + public <K, V> Consumer<K, V> create(Map<String, Object> configs) { + return createInternal(() -> { + if (useNewConsumer(configs)) { + return new AsyncKafkaConsumer<>(configs); + } else { + return new LegacyKafkaConsumer<>(configs); + } + }); + } + + public <K, V> Consumer<K, V> create(Properties properties) { + return createInternal(() -> { + if (useNewConsumer(properties)) { + return new AsyncKafkaConsumer<>(properties); + } else { + return new LegacyKafkaConsumer<>(properties); + } + }); + } + + public <K, V> Consumer<K, V> create(Properties properties, + Deserializer<K> keyDeserializer, + Deserializer<V> valueDeserializer) { + return createInternal(() -> { + if (useNewConsumer(properties)) { + return new AsyncKafkaConsumer<>(properties, keyDeserializer, valueDeserializer); + } else { + return new LegacyKafkaConsumer<>(properties, keyDeserializer, valueDeserializer); + } + }); + } + + public <K, V> Consumer<K, V> create(Map<String, Object> configs, + Deserializer<K> keyDeserializer, + Deserializer<V> valueDeserializer) { + return createInternal(() -> { + if (useNewConsumer(configs)) { + return new AsyncKafkaConsumer<>(configs, keyDeserializer, valueDeserializer); + } else { + return new LegacyKafkaConsumer<>(configs, keyDeserializer, valueDeserializer); + } + }); + } + + public <K, V> Consumer<K, V> create(ConsumerConfig config, + Deserializer<K> keyDeserializer, + Deserializer<V> valueDeserializer) { + return createInternal(() -> { + if (useNewConsumer(config.values())) { Review Comment: There's a lot of duplicated code for ``` if (useNewConsumer(config.values())) { return new AsyncKafkaConsumer<>(config, keyDeserializer, valueDeserializer); } else { return new LegacyKafkaConsumer<>(config, keyDeserializer, valueDeserializer); } ``` -- This is an automated message from the Apache Git Service. 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