Java 8 to 21 + spring boot 2 to 3 brought the need to change a lot of dependencies, but often they were drop-in replacements. That was mostly Jakarta stuff. On the Spring side, a lot of things we used were deprecated, but that was not related to the Java version.

Did not take a huge amount of time to upgrade anyway. But maybe our systems weren't the most complex in the first place, a lot of our applications were pretty small.

[–] spongebue@lemmy.world 5 points 1 week ago

That can also have its own dependencies. I tried to update some relatively simple apps that ran on Java 8 with some Spring libraries (not Boot) and had to deal with the Jakarta stuff to handle it... Only to discover that the Weblogic Application Server we use doesn't support Jakarta just yet (or probably more accurately, STILL doesn't!)