#3305 - fix default CharSequence serialization

[seregamorph]

Fixes #3305 and #3331 (dup).

[seregamorph]

I'm not quite sure about the policy with new protected methods, so I minimized the visibility for the first iteration

[cowtowncoder]

Thank you @seregamorph! I think the idea of the fix is sound -- I may want to tweak details a bit, but this makes sense to me. I'll add this on my TODO list: lately my time on Jackson has been severely limited and so it may take a while to get this processed, but I wanted to add a note that it is on my radar.

[seregamorph]

Sure, thanks.

[seregamorph]

@cowtowncoder I have a feeling that you plan to release the version soon with CVE. Can you please include this fix as well? We need it in our project. Thanks

[cowtowncoder]

@seregamorph Yes, I will definitely get this fix included first. It is next one on my list.

[cowtowncoder]

Thank you @seregamorph! I used this approach, only changing some of minor details (after checking if there might be other places to get rid of the property, finding no better one) -- thank you for suggesting the fix. I'll close the PR; fix will go in 2.13.1, which should be released some time this month (December 2021).

[seregamorph]

@cowtowncoder great, thanks!
Two questions:

1. Do you plan to backport it to 2.12.x as well? There is at least one good reason for it - spring-boot 2.5.7 depends on jackson 2.12.5 and on the same time spring-boot 2.5 is compatible with JDK 17. 2.5.x will probably be yet updated and I don't think they will do major version upgrade in scope of 2.5.x.
2. I'd recommend to include the test that I made as well (or something like it), in the future it can prevent possible regression.

[cowtowncoder]

I wasn't think of backporting, but maybe I should. Hard to gauge how important the fix is, vs. any potential regression.

As to test, yes, I added it, I think under src/test-jdk14. Although I realize now that it need not actually go there as it does not actually need more recent jdks (jdk14 just happened to already exist)

[cowtowncoder]

Patch was included in:

• 2.13.1
• 2.12.6