Dealing with null lists, v2.12

[Marcelo Carabolante]

Hello folks,

Is there any way to configure Jackson to treat null/missing list a empty collection?

context: we are using immutable objects, so its constructor based deserialization.

I tried a few stuff, but I always seems to hit a wall.

Thanks!

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[Tatu Saloranta]

On Fri, Mar 5, 2021 at 10:22 AM Marcelo Carabolante
<marcelo.c...@justeattakeaway.com> wrote:
>
> Hello folks,
>
> Is there any way to configure Jackson to treat null/missing list a empty collection?
>
> context: we are using immutable objects, so its constructor based deserialization.
>
> I tried a few stuff, but I always seems to hit a wall.

If what you want is to allow handling missing/null Collection value(s)
by one of:

1. Replace with default "empty" value
2. Throw exception
3. Skip assignment (for setter/field), to leave at default (presumable
empty) value

then what you want is the special form of `@JsonSetter` annotation (or
matching "config override" configuration).
It was added in 2.9, and explained on:

https://cowtowncoder.medium.com/jackson-2-9-features-b2a19029e9ff

So you'd add:

@JsonSetter(nulls=Nulls.AS_EMPTY)

on the specific accessor (field, setter, constructor parameter).
To handle the case of missing values (as opposed to just explicitly
received `null`s), you will need to apply it to constructor parameter.

Hope this helps,

-+ Tatu +-

>
> Thanks!
>
>
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