Hi Roman
Since we dont know in which context it is used I'd say null is a safer
default since Optional is poorly ontegrated with most frameworks but having
a global and local flag to switch would be nice.
Le 30 janv. 2016 18:11, "Roman Grigoriadi" <roman.grigoriadi_at_oracle.com> a
écrit :
> Hi experts.
>
> I have a question about marshalling / unmarshalling java 8 Optionals.
> Dmitry already made some suggestion about optionals, but lets elaborate a
> bit on them. They are a bit of special case. Logically Optional fields are
> not intended to be null, but technically it is possible. It makes some
> impact on marshalling / unmarshalling considerations.
>
> Basic question is: Should empty Optionals be skipped during serialization
> or serialized as keys with null values? Should optional properties honor
> @JsonbNillable configuration?
>
> Given a class:
>
> @JsonbNillable(true|false)
> class Pojo {
> Optional<Component> pojoComponent;
> String strField;
> }
>
> 1. Consider empty Optionals are serialized as missed in a JSON document
> and we also honor @JsonbNillable setting.
>
> If @JsonbNillable is set to true all is nice and easy:
>
> Pojo pojo = new Pojo();
> pojo.pojoComponent = Optional.empty(); //this have actually no effect on
> JSON document result
> jsonb.toJson(pojo);
> //Will produce {"pojoComponent":null,"strField":null} JSON.
> During unmarshalling of such JSON document we will set pojoComponent to
> Optional.empty()
>
>
> If @JsonbNillable is not set or set to false we will result with JSON:
>
> Pojo pojo = new Pojo();
> jsonb.toJson(pojo);
> //Will produce "{}" JSON.
>
> pojo.pojoComponent = Optional.empty();//no effect
> jsonb.toJson(pojo);
> //Will produce "{}" JSON again.
>
> Now when we will unmarshall such JSON document with missing keys for
> Optionals, we don't know if they were actually Optional empty or null.
> Furthermore, our JSONB Unmarshaller is driven by JSONP parser events, and I
> will get no event for any keys that are missing in document. So if I would
> like to set all Optional fields with null value to Optional.empty() (which
> makes most sense) it would have to be done by some kind of postprocessing.
>
> Things get even more complicated considering Arrays of Optionals. Array of
> Optionals of size 3 with either: 3 null values or 3 empty Optionals always
> have to be serialized as [null,null,null] in JSON document. It is
> inconsistent according to serializing Optional properties.
>
> Another option is not to honor @JsonbNillable setting and serialize null
> properties of Optionals as missing in JSON document and Optional.empty()
> values as JSON keys with null values. This will be consistent with Optional
> Arrays and we will explicitly know when and where to set Optional.emtpy()
> during unmarshalling, but it will be inconsistent with marshalling non
> Optional object properties set to null with @JsonbNillable set to false
> (default).
>
> Do you have any considerations about this?
>
> Thank you,
> Roman
>
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