Spring DefaultWebSessionManager should not cancel the subscription to WebSessionStore when there is no need to.

After receiving the first signal from WebSessionStore#retrieveSession the subscription on the Mono is cancelled which could confuse WebSessionStore implementations.

The flow currently is: request -> onNext -> cancel -> onComplete After the change the flow is: request -> onNext -> onComplete

Fixes gh-23606.

Author: Andreas Kluth mail@andreaskluth.net

Comment From: rstoyanchev

This is now taking the last session instead of the first session id. The lambda could return first but instead of reduce something like this would be more illustrative I think:

.collectList()
.filter(list -> !list.isEmpty())
.map(list -> {
        // list.get(0)
        // ...
})

Comment From: AndreasKl

@rstoyanchev DefaultWebSessionManagerTests#multipleSessionIds validates that the last session id is returned. I broke the test when I just returned the first element with Stream#findFirst which was my obvious first choice. I could replace the reduce with some variation or most likely more readable with an imperative condition.

I'm not sure if it would be a breaking change when I just return the first element and amend DefaultWebSessionManagerTests#multipleSessionIds.

Comment From: rstoyanchev

Oh I see. Actually it isn't about the last session id, but rather the first session id for which a session is found. In the test retrieveSession happens to return empty for the first two.

Given this I'm not sure we could rewrite without cancelling after the first found session. The only alternative would be to try and retrieve all sessions, collectToList, and pick the first.

Comment From: AndreasKl

I think then we should close this PR, as I now understand what the purpose of the code was :-)

Thank you for your time.