Use simple session repository implementations by default

[vpavic]

As discussed with @rwinch some while ago, Spring Session should use simpler, more performant session repository implementations by default. The 3.0 release as the next major release is a natural place to consider such a change. This was actually the motivation for coming up with RedisSessionRepository in 2.2.

Specifically, at this point this is about RedisIndexedSessionRepository vs RedisSessionRepository. The indexed variant supports fetching sessions by index (i.e. implements FindByIndexNameSessionRepository) as well as session events. These features add quite a bit of complexity implementation wise and benefits (indexes and events) aren't even used by most of the users these day.

While making this change, we should also make sure that it's easy for the users to opt-in to other available session repository implementations.

Related issues:

• Why are there so many redis requests happening? #1182

[dreis2211]

are even used by most of the users these day.

@vpavic used or unused? The change wouldn't make much sense imho, if most of the users actually use session events and index based fetching.

Cheers,
Christoph

[vpavic]

That are at the beginning of the quote was really supposed to be aren't. 🙂
Thanks @dreis2211, I've updated the original comment.