[spring] fix default value for nullable containers

[wing328]

• To fix [BUG][Java] Nullable array creates assignments without value #14948 (incorrect default values make code not compilable)
• add new cases in test spec
• migrate test spec used by spring from 2.0 to 3.0

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cc @cachescrubber (2022/02) @welshm (2022/02) @MelleD (2022/02) @atextor (2022/02) @manedev79 (2022/02) @javisst (2022/02) @borsch (2022/02) @banlevente (2022/02) @Zomzog (2022/09)

[borsch]

what if openApiNullable=false & no default value?

[wing328]

good catch, i just spotted the same issue with #14961.

i think we will need to create an empty container (array or set) if it's null.

[wing328]

pushed a fix. please have another look when you've time. thanks.

[welshm]

Code change looks fine. I think you have unrelated changes here

Just one question about error cases.

[welshm]

I wouldn't expect some of these changes from your mustache changes - bad branch?

[wing328]

in 3.x spec, the schema name must conform to

	-components.schemas.Schema name $special[model.name] doesn't adhere to regular expression ^[a-zA-Z0-9\.\-_]+$

(this PR also migrates test spec used by spring from 2.0 to 3.0)

[welshm]

If the value is removed when required is true - does Jackson or something else validate it is set at some point?

Otherwise, will responses to clients will fail because a required field is missing?

I do realize that required means that a default value shouldn't be used. Just trying to think of how the error scenario is detected.

[wing328]

looks like @NotNull should be used instead per https://stackoverflow.com/a/45877203/677735

(I think it's out of scope of this PR which aims to fix the default value)

[wing328]

FYI. Filed #14981 to migrate remaining config files related to spring generators to use 3.x spec.

[noshua]

Something in the 7.5.0 release toggled the behavior for me. On 7.4.0 all collections where default to null now with 7.5.0 all collections are initialized empty. Since you seem to be familiar with this topic @wing328 any idea what changed in the last release?