javajacksonyamlsnakeyaml

Jackson YAML: support for anchor extensions/overrides

I'm trying to use Jackson 2.15.2 YAMLFactory to parse the anchor extension syntax:

sections:
- &packetInfo
    name: packetInfo
    description: information on a received UDP packet

and then later:

sections:
-   <<: *packetInfo
    description: something else

But I'm getting: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "<<" , and it's giving all the signs of treating the << as any other field name.

If I remove the <<: like this, it loads ok (without the option to override, of course), so the anchor/reference system is working:

sections:
-   *packetInfo

Does Jackson not support <<: extension/overrides? Or is there a Feature switch I need to turn on that I haven't found yet? I've read that handling these is done by a schema, rather than the parser itself.

Solution

  • Jackson is known to not handle references correctly.

    You can use SnakeYAML directly which does support references and the merge key <<. Jackson uses SnakeYAML under the hood anyway but somehow screws this up.

    SnakeYAML has pretty much the same capabilities as Jackson so there isn't much of a reason why you'd need to stick to Jackson.