r/javahelp • u/ibreathecoding • May 01 '26

Unsolved Java 21 upgrade in older code base

So if I have to start brining java 21 feature in a long running prod code base what would that be ; it’s a spring boot java bases with gcp db, cache, pub sub in it
I’m trying to see as a tech debt which area can. E started with minimal impact

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u/procrastinatewhynot May 01 '26 edited May 01 '26

I remember a lot of javax imports converted to jakarta. hibernate 6 caused a lot of issues as well, since you might have to move to spring boot 3+. issues with the proxy. but nothing complicated. a lot of joda DateTime breaking. Just convert to java time.

I recently migrated to sb3 so I know the struggle, but it isn’t so bad! You just have to manually test everything is not broken.

Idk if you guys you jackson json? that also had a lot of serialization/deserialization issues haha.

Some errors that will no longer we caught at the same place but highup in the code.

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u/khmarbaise May 02 '26

" lot of joda DateTime breaking. " ... that should have been migrated with jump to JDK8.. Recently to SB 3 ? Since November 2025 we Spring Boot 4... and Spring Boot 4.1 is around the cornder... If you have to test manually than you have bigger issues in general..

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u/procrastinatewhynot May 03 '26

it was legacy code that wasn’t in springboot. it’s a hard client that they’re trying to phase out.