Adds @Nullable annotation to Spring Boot generator

[slobodator]

Motivations:

• Have Spring Boot generator client properly annotated for nullability to be able to check code using them with tools like NullAway to close

• issue-14427: [REQ][spring] Null-Safety annotations
• issue-17382: [REQ] spring generator add Nullable annotations

• As it is related to Spring then the org.springframework.lang.Nullable annotation was chosen to avoid discussion which @Nullable one is true one
• @NonNull wasn't used as I didn't see much benefit of it. Anyhow, an empty constructor and/or setters allow to put a null value there

Modifications:

• Adds the nullableAnnotation template to handle nullability annotation on vars
• Adjust pojo templates to use the nullability template
• Adapts tests

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[slobodator]

@cachescrubber @welshm @MelleD @atextor @manedev79 @javisst @borsch @banlevente @Zomzog @martin-mfg

Folks, please, have a look

[slobodator]

Split that into 2 commits for an easier review.

A bit confused why adding the import of org.springframework.lang.Nullable at SpringCodegen affected the java-camel samples ((( Seems to be an issue

[slobodator]

It turned out that JavaCamelServerCodegen extends SpringCodegen but I added a safety net not to affect it, please, see my 3rd commit

[MelleD]

I think for JsonNullable and when you using using Collection which could no be null it make also no sense to set this annotation

[MelleD]

And one more question do you think this make sense when you using bean validation?

[slobodator]

Hi @MelleD,

Thank for your quick review, appreciate it.

for JsonNullable

Indeed, that was already taken into consideration. If the field is wrapped with either JsonNullable or Optional it will not be annotated with @Nullable. Please, see the tests at the 1st commit.

using Collection

Actually, it is not about just collection but any property with default value. For collections it was more obvious. My fault, thank you for catching it. Fixed that at the 4th commit (and updated samples again at the 5th commit)

when you using bean validation

If I got you right, it is not intersected. See: any property which is not required might be null. Any validation (except @NotNull of course) bypasses and should bypass any nulls, which is correct. So, the bean validation doesn't prevent NPEs and it is worth to annotate such fields, I guess

[MelleD]

Indeed, that was already taken into consideration. If the field is either wrapped with JsonNullable or Optional it is not annotated with @Nullable. Please, see the tests at the 1st commit.

Ah I missed that, I just saw useOptional and thought maybe JsonNullable make also no sense :-)

If I got you right, it is not intersected. See: any property which is not required might be null. Any validation (except @NotNull of course) bypasses and should bypass any nulls, which is correct. So, the bean validation doesn't prevent NPEs and it is worth to annotate such fields, I guess

Ok sounds reasonable. For a while I don't use nulls (I use Optional/Enum instead).

[slobodator]

I have some thoughts regarding Optional but let's discuss them as a separate story. For the moment my colleagues use just regular objects, and I would like to make their life easier with handling NPEs

[MelleD]

I have some thoughts regarding Optional

It's fine there is no right or wrong everybody have own opinion about Optional.(https://medium.com/97-things/using-optional-nowhere-somewhere-or-everywhere-b1eb5645eab5)

I just say that I have not much experience with null handling ;)

[MelleD]

PR looks good.

It is still an open point whether a property like useBeanValidation or useOptional makes sense to switch the annotation on and off. Maybe we should ask other users @wing328 @borsch @martin-mfg

What do you think?

[slobodator]

useOptional makes sense to switch the annotation on and off

Sorry for jumping in again but useOptional:true definitely offs this annotation. Please, see the shouldNotAnnotateNonRequiredFieldsAsNullableWhileUseOptional test

a property like useBeanValidation

Any validator (except NotNullValidator of course), i.e. org.hibernate.validator.internal.constraintvalidators.bv.EmailValidator or PatternValidator or anything else starts with

  public boolean isValid(CharSequence value, ConstraintValidatorContext context) {
    if (value == null) {
      return true;

[MelleD]

Sorry for jumping in again but useOptional:true definitely offs this annotation. Please, see the shouldNotAnnotateNonRequiredFieldsAsNullableWhileUseOptional test

Yes true but what is when you would like to use nulls without this annotation? You think everybody would like to use it?
When yes then iam fine with this PR. Was just a question to some other users ;), because iam not using it.

[slobodator]

when you would like to use nulls without this annotation?

That was a reason why I didn't introduce @Nonnull annotation )
I don't state that something is non-nullable.
I only want to highlight that non-required fields (if they are not wrapper with either Optional or JsonNullable) might be nulls.

You think everybody would like to use it? .... because iam not using it.

If I got you right, you seem to be from the optional-everywhere camp. Well, if the useOptional option is turned on everything is much stricter, I totally agree. Then my PR won't inject @Nullable annotation for those fields, of course.

Still, useOptional:false is by default and used (at least at our projects). Indeed, the @Nullable is nothing more than an IDE/static analyser warning but is a bit better than nothing for those who didn't turn on useOptional.

When yes then iam fine with this PR. Was just a question to some other users ;),

Beg your pardon, I am talking too much. Let's wait for @wing328 @borsch @martin-mfg opinions.

[MelleD]

How I said Iam fine with the PR thanks 😊 . Just collect some other opinions is there somebody who would like to turn it off to prevent some new issues: “how can I remove this annotation” 😂