[FLINK-12141] Allow @TypeInfo annotation on POJO field declarations

• Type: New Feature
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 1.14.0
• Component/s: API / Type Serialization System
• Labels: auto-unassigned pull-request-available starter usability
• Release Note: @TypeInfo annotations can now also be used on POJO fields which, for example, can help to define custom serializers for third-party classes that can otherwise not be annotated themselves.
• Assignee: Nico Kruber
• Reporter: Gyula Fora
• Created: 09/Apr/19 08:48
• Updated: 16/Aug/21 18:47
• Resolved: 16/Aug/21 18:47

Description

The TypeInfo annotation is a great way to declare serializers for custom types however I feel that it's usage is limited by the fact that it can only be used on types that are declared in the project.

By allowing the annotation to be used on field declarations we could improve the TypeExtractor logic to use the type factory when creating the PojoTypeInformation.

This would be a big improvement as in many cases classes from other libraries or collection types are used within custom Pojo classes and Flink would default to Kryo serialization which would hurt performance and cause problems later.

The current workaround in these cases is to implement a custom serializer for the entire pojo which is a waste of effort when only a few fields might require custom serialization logic.

Issue Links

• links to: GitHub Pull Request #8344