Derialize/deserialize to a Map<String, Object> with type for bean and no type for primitive/collection/map

[nit...@gmail.com]

Hello,

I hope my question will not be another "why doesn't Jackson find polymorphic type for my Map values (or List or Set)" and  I hope I did my best to check for any question/answer :).

I have a bean with an any field: 

@JsonAnyGetter
@JsonAnySetter
protected Map<String, Object> properties = new HashMap<>();

When initializing the map with:

properties.put("foo", new FooBean());

properties.put("foos", List.of(new FooBean()));

properties.put("long", 123);

properties.put("longs", List.of(123));

properties.put("longss", List.of(List.of(123)));

I want to produce:

{
"foo": {
"@class": "org.FooBean", "foo": "bar"
},
"foos": [
{
"@class": "org.FooBean", "foo": "bar"
}
],
"long": 123,
"longs": [123, 567],

"longss": [[123], 567]
}

ie. a type for bean but not for primitive or collection/map.

Is this use case achievable by using jackson? To quote that post  if there'd be an option that says, if there is a type attribute at the beginning, create this type, rather than a natural one. 

Thanks for your help

Nicolas

[Nicolas Labrot]

I think for the moment I will try to create a custom serializer / deserializer for my properties map

- Serializer: introspect the map and build JavaType then call the appropriate serialize 

- Deserializer: convert first into a TreeNode and then introspect the TreeNode (basically, if map and @type then try to create the associated deserializer)

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[Tatu Saloranta]

On Mon, Jul 18, 2022 at 4:47 AM Nicolas Labrot <nit...@gmail.com> wrote:
>
> I think for the moment I will try to create a custom serializer / deserializer for my properties map
> - Serializer: introspect the map and build JavaType then call the appropriate serialize
> - Deserializer: convert first into a TreeNode and then introspect the TreeNode (basically, if map and @type then try to create the associated deserializer)
>

Ok so:

1. No, I don't think there is a way to make Polymorphic handling work
with "Any" properties with `Object` as value
2. But if you just have `Map<String,Object>`, you SHOULD be able to
simply use `@JsonTypeInfo` annotation on Map property (field or
accessor)

So I would first try (2), I think.

It _might_ just work with `@JsonValue` as well, if you needed
"JsonAnySetter/Getter"-like behavior.

-+ Tatu +-

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[nit...@gmail.com]

Thanks for your answer.

Without the any setter/getter but with JsonTypeInfo on the map field, the @class are added to every entries at the exclusion of the java types mappable into json (so Long at its @class). But List<Integer> still have its @class. 

Without the any setter/getter, without JsonTypeInfo on the map field but with JsonTypeInfo on all the pojo classes that can be inserted into the map,  the @class are only added to those entries but at the deserialization the entry having @class are not recovered but transformed into a map 

I end up writing my own serializer / deserializer :)

https://gist.github.com/nithril/b55d6ab32db253dfe24995f87c899685

[Tatu Saloranta]

On Tue, Jul 19, 2022 at 12:44 PM nit...@gmail.com <nit...@gmail.com> wrote:
>
> Thanks for your answer.
>
> Without the any setter/getter but with JsonTypeInfo on the map field, the @class are added to every entries at the exclusion of the java types mappable into json (so Long at its @class). But List<Integer> still have its @class.
> Without the any setter/getter, without JsonTypeInfo on the map field but with JsonTypeInfo on all the pojo classes that can be inserted into the map, the @class are only added to those entries but at the deserialization the entry having @class are not recovered but transformed into a map

Ok, I am sure I follow the details here, but sounds like this does not
work the way you would like it to work.

And wrt generic container types (that is, `List<X>`), no type
information is available thanks to type erasure, that is true.

> I end up writing my own serializer / deserializer :)
> https://gist.github.com/nithril/b55d6ab32db253dfe24995f87c899685

Ok, sometimes that's what you got to do. Good luck!

-+ Tatu +-

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