@JsonProperty required = true does not work for constructors

[christophsturm]

for example with this constructor

    public Strategy(@JsonProperty(value = "hehe") int hehe,@JsonProperty(value = "blah", required = true) int blah)

I can still deserialize a json that does not contain blah.

I did not see this documented anywhere, just in the changelog for 2.1.0:

* [Issue#9]: Implement 'required' JSON Schema attribute for bean properties

so i guess constructor support for this feature is just missing. is that correct?

[cowtowncoder]

Correct. More generally, 'required' attribute is not supported for deserialization at all -- supporting it will require surprisingly significant changes in deserializer. So if/when this is done, it should also be made to work with creator methods.

[robertkuhar]

I would really like to see this implemented. I expected that "required" worked both ways and was surprised to learn that it didn't.

[cowtowncoder]

Yup, we are always open for good code contributions!

[lukens]

I came across this issue after making a similar assumption about what the behaviour would be.

I would, however, also comment that if you expect a value passed to a constructor to be non-null, then it should be non-null whether deserialised from JSON or constructed otherwise. As such, even if this was enforced through the @JsonProperty annotation when deserialising, you could still construct an invalid instance of the class through other means. I therefore feel it is better to check for non-null values in the constructor code itself.

Of course, if you only ever construct your objects through JSON deserialisation you probably less concerned about this.

[cowtowncoder]

I think this is dup of #230, so closing as such -- still hoping to add support for checks in future, just want to reduce duplication in issue tracker.

[cowtowncoder]

Correction: this was not exact dup of #230, being a subset.

But we do have #781 -- just implemented for 2.6.0! -- which was re-filed for the specific case of supporting required-ness for Creator methods. This because that subset is relatively easy to support, and is needed to support some Scala functionality as well.