Flink still use PojoSerializer for the class while only using Kryo for the UUID field.
Best, Zhanghao Chen ________________________________ From: Richard Cheung <rcheungsi...@gmail.com> Sent: Wednesday, May 14, 2025 3:21 To: user@flink.apache.org <user@flink.apache.org> Subject: Apache Flink Serialization Question Hi all! I have a question about serialization of POJO data classes in Apache Flink v1.8 (Java). Here's some context: One of my data classes was initially not POJO compatible as it had final fields and no no-arg constructor. I removed the final modifiers and added a no-arg constructor, and confirmed that the serializer switched from KryoSerializer to PojoSerializer using TypeInformation and TypeSerializer to log the info. However, one of the fields in the class is a java.util.UUID, which is not POJO compatible. I see a log message saying that the UUID field cannot be used as a POJO type. The logs also say that the UUID field will be processed as a generic type which means that, to my knowledge, the KryoSerializer will be used. These logs appear after the one indicating that the PojoSerializer is being used for my data class. My question is: Does the presence of the UUID field cause the entire class to be serialized with KryoSerializer or does Flink still use PojoSerializer for the class while only using Kryo for the UUID field? Best regards, Richard
