JSON Patch Request validation in Java
Under many circumstances you can just patch an intermediate object which only has fields that the user can write to. After that you could quite easily map the intermediate object to your entity, using some object mapper or just manually.
The downside of this is that if you have a requirement that fields must be explicitly nullable, you won’t know if the patch object set a field to null explicitly or if it was never present in the patch.
What you can do too is abuse Optionals for this, e.g.
public class ProjectPatchDTO { private Optional<@NotBlank String> name; private Optional<String> description;}Although Optionals were not intended to be used like this, it's the most straightforward way to implement patch operations while maintaining a typed input. When the optional field is null, it was never passed from the client. When the optional is not present, that means the client has set the value to null.