Why Spring KafkaTemplate doesn't set its instance variable "messageConverter" to volatile?

Question

I was reading source code of Spring KafkaTemplate(org.springframework.kafka.core) and came across this piece of code:

protected final Log logger = LogFactory.getLog(this.getClass()); //NOSONAR

private final ProducerFactory<K, V> producerFactory;

private final boolean autoFlush;

private final boolean transactional;

private final ThreadLocal<Producer<K, V>> producers = new ThreadLocal<>();

private RecordMessageConverter messageConverter = new MessagingMessageConverter();

private volatile String defaultTopic;

private volatile ProducerListener<K, V> producerListener = new LoggingProducerListener<K, V>();

As you see, variables like defaultTopic and producerListener are set to volatile which I presume to make them memory visible once being changed.

So I am confused why meesageConverter was not set to the same.

Answer 1

We generally don't expect configuration properties, such as the message converter to be changed at runtime so there is no need to make it volatile. If you have such a requirement, subclass the template and override the setter with a synchronized method (calling super.set...()).

You are looking at an older version of the code; those variables are no longer volatile.