Description
In what version(s) of Spring for Apache Kafka are you seeing this issue?
2.8.2
Describe the bug
DefaultKafkaHeaderMapper is registering a SimpleModule in constructor to the given ObjectMapper instance. Since the SimpleModule's are unnamed modules, IGNORE_DUPLICATE_MODULE_REGISTRATIONS configuration of ObjectMapper doesn't handle multiple registration of this module. This is problematic and can cause a memory leak if the DefaultKafkaHeaderMapper(ObjectMapper mapper) constructor is called with the same ObjectMapper instance multiple times.
To Reproduce
Call the DefaultKafkaHeaderMapper(ObjectMapper mapper) function with same ObjectMapper instance multiple times.
Expected behavior
A new SimpleModule would be registered to the ObjectMapper beacuse of the new SimpleModule().addDeserializer(MimeType.class, new MimeTypeJsonDeserializer()) call.
Solution
This problematic situation can be avoided simply by giving a name to the SimpleModule created as below:
this.objectMapper.registerModule(new SimpleModule("mimeTypeJsonDeserializer", Version.unknownVersion())
.addDeserializer(MimeType.class, new MimeTypeJsonDeserializer()));