Sorting nested ObjectNode values alphabetically

[mark r]

Hello!


I'm trying to serialize an ObjectNode value that contains nested ObjectNode
values. What is the correct way to have Jackson serialize the keys in alphabetical
order? Bear in mind that I don't actually know the structure of the ObjectNodes
before I serialize them; only that they're effectively arbitrarily nested key/value
structures.

I've seen the Stack Overflow answers:

https://stackoverflow.com/questions/27577701/jackson-objectmapper-specify-serialization-order-of-object-properties

... And they're either not relevant to my problem (specifying annotations on
classes used for deserialization when I'm dealing with ObjectNodes I didn't
deserialize), or specify various combinations of the MapperFeature.SORT_PROPERTIES_ALPHABETICALLY,
or SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS flags,
which don't appear to have any effect.

My code essentially looks like this:

```

  fun canonicalize(

    objectNode: ObjectNode,

    outputStream: OutputStream

  ) {

    val mapper = ObjectMapper()

    mapper.configure(SerializationFeature.INDENT_OUTPUT, false)

    mapper.configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true)

    mapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true)

    mapper.writeValue(outputStream, objectNode)

  }

```

The data written to the output stream does _not_ have the keys sorted

in alphabetical order.

Any help would be appreciated!

[Tatu Saloranta]

On Fri, Jul 24, 2020 at 9:16 PM mark r <rm....@gmail.com> wrote:
>
> Hello!
>
>
> I'm trying to serialize an ObjectNode value that contains nested ObjectNode
> values. What is the correct way to have Jackson serialize the keys in alphabetical
> order? Bear in mind that I don't actually know the structure of the ObjectNodes
> before I serialize them; only that they're effectively arbitrarily nested key/value
> structures.

Tree model (JsonNode / ObjectNode) is meant to represent JSON content
exactly as-is, with few if
any transformations, and is handled quite differently from POJOs.
As such there is no auto-sorting feature at this point, although there
are some plans to maybe add support:

https://github.com/FasterXML/jackson-future-ideas/wiki/JSTEP-3

However: you should be able to convert `ObjectNode` into `Map` (or
just `Object` more generally) with

Map<String, Object> map = mapper.treeToValue(node, Map.class);

after which `SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS` should
work on serialization.
So 2-step processing should handle this particular case.

-+ Tatu +-

[rm....@gmail.com]

On 2020-07-26T16:05:44 -0700

Tatu Saloranta <ta...@fasterxml.com> wrote:
>
> Tree model (JsonNode / ObjectNode) is meant to represent JSON content
> exactly as-is, with few if
> any transformations, and is handled quite differently from POJOs.
> As such there is no auto-sorting feature at this point, although there
> are some plans to maybe add support:
>
> https://github.com/FasterXML/jackson-future-ideas/wiki/JSTEP-3
>
> However: you should be able to convert `ObjectNode` into `Map` (or
> just `Object` more generally) with
>
> Map<String, Object> map = mapper.treeToValue(node, Map.class);
>
> after which `SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS` should
> work on serialization.
> So 2-step processing should handle this particular case.

Hello!

Does `treeToValue` handle nested ObjectNodes? I'm actually implementing
JSON canonicalization [0]. In Jackson right now, serialization without
indentation fulfills all of the requirements of canonicalization except
for the sorting of keys on serialization.

I can certainly walk the entire tree myself, but I'd prefer not to have
to. :)

[0]https://tools.ietf.org/id/draft-rundgren-json-canonicalization-scheme-00.html

--
Mark Raynsford | https://www.io7m.com

[Tatu Saloranta]

On Mon, Jul 27, 2020 at 1:15 AM <rm....@gmail.com> wrote:
>
> On 2020-07-26T16:05:44 -0700
> Tatu Saloranta <ta...@fasterxml.com> wrote:
> >
> > Tree model (JsonNode / ObjectNode) is meant to represent JSON content
> > exactly as-is, with few if
> > any transformations, and is handled quite differently from POJOs.
> > As such there is no auto-sorting feature at this point, although there
> > are some plans to maybe add support:
> >
> > https://github.com/FasterXML/jackson-future-ideas/wiki/JSTEP-3
> >
> > However: you should be able to convert `ObjectNode` into `Map` (or
> > just `Object` more generally) with
> >
> > Map<String, Object> map = mapper.treeToValue(node, Map.class);
> >
> > after which `SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS` should
> > work on serialization.
> > So 2-step processing should handle this particular case.
>
> Hello!
>
> Does `treeToValue` handle nested ObjectNodes? I'm actually implementing

Yes, it should work recursively; it is full "convertValue()" just with
input value restriction.

> JSON canonicalization [0]. In Jackson right now, serialization without
> indentation fulfills all of the requirements of canonicalization except
> for the sorting of keys on serialization.

Ah. It might make sense to file an RFE issue asking for sorting of
ObjectNode entries as this seems like
a legit use case. As I mentioned it is sort of on my radar as wish,
but as part of bunch of other "JsonNode features".
Sometimes a separate issue makes it easier to prioritize such features.

> I can certainly walk the entire tree myself, but I'd prefer not to have
> to. :)

Yes, makes sense.

>
> [0]https://tools.ietf.org/id/draft-rundgren-json-canonicalization-scheme-00.html

-+ Tatu +-