Add Kafka shared consumer container support

- New AbstractShareKafkaMessageListenerContainer base class with lifecycle management
- ShareKafkaMessageListenerContainer implementation for share consumer protocol
- Integration tests for end-to-end message delivery validation

Signed-off-by: Soby Chacko <[email protected]>

Author: sobychacko

spring-kafka/src/main/java/org/springframework/kafka/listener/AbstractShareKafkaMessageListenerContainer.java

@@ -0,0 +1,247 @@
+/*
+ * Copyright 2025-2025 the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.springframework.kafka.listener;
+
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.regex.Pattern;
+
+import org.apache.commons.logging.LogFactory;
+import org.apache.kafka.clients.consumer.ConsumerConfig;
+import org.jspecify.annotations.Nullable;
+
+import org.springframework.beans.BeanUtils;
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.BeanNameAware;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationContextAware;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.context.ApplicationEventPublisherAware;
+import org.springframework.core.log.LogAccessor;
+import org.springframework.kafka.core.ShareConsumerFactory;
+import org.springframework.kafka.support.TopicPartitionOffset;
+import org.springframework.util.Assert;
+
+/**
+ * Abstract base class for share consumer message listener containers.
+ * <p>
+ * Handles common lifecycle, configuration, and event publishing for containers using a
+ * {@link org.springframework.kafka.core.ShareConsumerFactory}.
+ * <p>
+ * Subclasses are responsible for implementing the actual consumer loop and message dispatch logic.
+ *
+ * @param <K> the key type
+ * @param <V> the value type
+ *
+ * @author Soby Chacko
+ * @since 4.0
+ */
+public abstract class AbstractShareKafkaMessageListenerContainer<K, V>
+		implements GenericMessageListenerContainer<K, V>, BeanNameAware, ApplicationEventPublisherAware,
+		ApplicationContextAware {
+
+	/**
+	 * The default {@link org.springframework.context.SmartLifecycle} phase for listener containers.
+	 */
+	public static final int DEFAULT_PHASE = Integer.MAX_VALUE - 100;
+
+	protected final ShareConsumerFactory<K, V> shareConsumerFactory;
+
+	protected final LogAccessor logger = new LogAccessor(LogFactory.getLog(this.getClass()));
+
+	private final ContainerProperties containerProperties;
+
+	protected final ReentrantLock lifecycleLock = new ReentrantLock();
+
+	private String beanName = "noBeanNameSet";
+
+	@Nullable
+	private ApplicationEventPublisher applicationEventPublisher;
+
+	private boolean autoStartup = true;
+
+	private int phase = DEFAULT_PHASE;
+
+	@Nullable
+	private ApplicationContext applicationContext;
+
+	private volatile boolean running = false;
+
+	/**
+	 * Construct an instance with the provided factory and properties.
+	 * @param shareConsumerFactory the factory.
+	 * @param containerProperties the properties.
+	 */
+	@SuppressWarnings("unchecked")
+	protected AbstractShareKafkaMessageListenerContainer(@Nullable ShareConsumerFactory<? super K, ? super V> shareConsumerFactory,
+														ContainerProperties containerProperties) {
+		Assert.notNull(containerProperties, "'containerProperties' cannot be null");
+		Assert.notNull(shareConsumerFactory, "'shareConsumerFactory' cannot be null");
+		this.shareConsumerFactory = (ShareConsumerFactory<K, V>) shareConsumerFactory;
+		@Nullable String @Nullable [] topics = containerProperties.getTopics();
+		if (topics != null) {
+			this.containerProperties = new ContainerProperties(topics);
+		}
+		else {
+			Pattern topicPattern = containerProperties.getTopicPattern();
+			if (topicPattern != null) {
+				this.containerProperties = new ContainerProperties(topicPattern);
+			}
+			else {
+				@Nullable TopicPartitionOffset @Nullable [] topicPartitions = containerProperties.getTopicPartitions();
+				if (topicPartitions != null) {
+					this.containerProperties = new ContainerProperties(topicPartitions);
+				}
+				else {
+					throw new IllegalStateException("topics, topicPattern, or topicPartitions must be provided");
+				}
+			}
+		}
+		BeanUtils.copyProperties(containerProperties, this.containerProperties,
+				"topics", "topicPartitions", "topicPattern");
+	}
+
+	@Override
+	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
+		this.applicationContext = applicationContext;
+	}
+
+	@Nullable
+	public ApplicationContext getApplicationContext() {
+		return this.applicationContext;
+	}
+
+	@Override
+	public void setBeanName(String name) {
+		this.beanName = name;
+	}
+
+	/**
+	 * Return the bean name.
+	 * @return the bean name
+	 */
+	public String getBeanName() {
+		return this.beanName;
+	}
+
+	@Override
+	public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
+		this.applicationEventPublisher = applicationEventPublisher;
+	}
+
+	/**
+	 * Get the event publisher.
+	 * @return the publisher
+	 */
+	@Nullable
+	public ApplicationEventPublisher getApplicationEventPublisher() {
+		return this.applicationEventPublisher;
+	}
+
+	@Override
+	public boolean isAutoStartup() {
+		return this.autoStartup;
+	}
+
+	@Override
+	public void setAutoStartup(boolean autoStartup) {
+		this.autoStartup = autoStartup;
+	}
+
+	@Override
+	public int getPhase() {
+		return this.phase;
+	}
+
+	public void setPhase(int phase) {
+		this.phase = phase;
+	}
+
+	@Override
+	public void stop(Runnable callback) {
+		stop();
+		callback.run();
+	}
+
+	@Override
+	public void start() {
+		this.lifecycleLock.lock();
+		try {
+			if (!isRunning()) {
+				Assert.state(this.containerProperties.getMessageListener() instanceof GenericMessageListener,
+						() -> "A " + GenericMessageListener.class.getName() + " implementation must be provided");
+				doStart();
+			}
+		}
+		finally {
+			this.lifecycleLock.unlock();
+		}
+	}
+
+	@Override
+	public void stop() {
+		this.lifecycleLock.lock();
+		try {
+			if (isRunning()) {
+				doStop();
+			}
+		}
+		finally {
+			this.lifecycleLock.unlock();
+		}
+	}
+
+	@Override
+	public boolean isRunning() {
+		return this.running;
+	}
+
+	protected void setRunning(boolean running) {
+		this.running = running;
+	}
+
+	@Override
+	public ContainerProperties getContainerProperties() {
+		return this.containerProperties;
+	}
+
+	@Override
+	@Nullable
+	public String getGroupId() {
+		return this.containerProperties.getGroupId() == null
+				? (String) this.shareConsumerFactory.getConfigurationProperties().get(ConsumerConfig.GROUP_ID_CONFIG)
+				: this.containerProperties.getGroupId();
+	}
+
+	@Override
+	public String getListenerId() {
+		return this.beanName; // the container factory sets the bean name to the id attribute
+	}
+
+	@Override
+	public void setupMessageListener(Object messageListener) {
+		this.containerProperties.setMessageListener(messageListener);
+	}
+
+	protected abstract void doStart();
+
+	protected abstract void doStop();
+
+	@Override
+	public void destroy() {
+		stop();
+	}
+}