Add support for basic "is-required" checks on deserialization using `@JsonProperty(required=true)`

[cowtowncoder]

(note: moved from https://jira.codehaus.org/browse/JACKSON-767)

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As per title, although full validation of values is out-of-scope for Jackson, very basic "must be included in JSON" checks may fall in 80/20 line of things. Especially since we already have annotation to use.

The trick here is implementation; from two distinct parts:

1. This requires handling and retaining of extra state (what has been included) during deserialization by BeanDeserializer, and passing it; not trivial to do with current code.
2. Due to combinatorial explosion by features, efficiency, we need to be careful not to add Yet Another combination of things to tackle, requiring adding yet more similar (but not identical) methods

[theon]

This would be really useful for us for generating JSON Schema. In JSON Schema properties are optional by default and need to be explicitly marked as required.

See FasterXML/jackson-module-scala#80

[cowtowncoder]

As far as I know, this is already being used for schema generation. In fact, the only real use for the property.
This should at least be the case for the external json schema module.

[theon]

You are of course correct 😃 I've tested this with both the external json schema module and the jackson-databind schema generation and both respect the required property in the @JsonProperty annotation.

[cowtowncoder]

Some good news: #781 -- which adds support for required-ness for Creator methods -- has been implemented, and will be in 2.6. I hope it also helps figure out eventual general implementation for required.
And perhaps even support for default values, in distant future.

[operatiay]

2.6.0-rc4 doesn't work for me.

I've added
objectMapper.configure(DeserializationFeature.FAIL_ON_MISSING_CREATOR_PROPERTIES, true);
without any effect.

[walec51]

Did you use this annotation on a constructor method ?
It does not work on class attributes. That's why this issue is still open.

[operatiay]

thank you @walec51 . Constructor annotation did work for me.

[utsengar]

Do we have an update on this for class attributes? Been 1yr since last update.

[cowtowncoder]

@utkarsh2012 If there is work we will update the issue. There is not much point in asking for things when there is no indication anything has changed. If you want to ask questions, in general, mailing list is a better place.