What are the likely pain points to upgrade an application to Spring 3.0

Question

Given an application using Spring 2.5, when migrating to Spring 3.0 what are the likely areas that will be pain points, i.e. things that the development team will have to spend time on to get things working. Assume the team would not try to take advantage of new Spring features as part of the upgrade, but just get the application to the state where it works as it did on 2.5. Taking advantage of 3.0 features would be the next steps to consider.

Edit: I have revised the question to focus on the pain points of the upgrade, which is what I'm really after.

Answer 1

If you're lucky, then nothing will need changing, it should all just work. The Spring guys are very careful to retain backwards compatibility.

The biggest reason I can think of for it not working is if you're using code that was deprecated in 2.5, and marked for removal in 3.0 You can find that list here.

Answer 2

Probably the biggest change in Spring 3.0 is that it now requires J2SE 5.0.

One of the Spring developers reply for a compatibility question in this blog entry.

Spring 3.0 aims to be 99% backwards compatible with Spring 2.5. The core APIs and SPIs will remain stable in order to keep existing extensions (and of course also existing application code) working. Introducing generics and varargs, as we've done in M1 and M2, should still preserve binary compatibility. That said, we generally recommend rebuilding your applications for Spring 3.0, in order to catch potential API issues early. This will also allow you to get the maximum benefit from Spring 3.0's Java 5 API refinements.