Add SingleResultAuthorizationManager

[franticticktick]

Closes gh-16590

[franticticktick]

Hey @plll0123, we invite you to join the review so that your interest in contributions does not disappear :)

[jzheaux]

Thanks again, @franticticktick! I've left my feedback inline. Note that most if it is based on the premise that I think it class should hold an AuthorizationResult member variable, set in the constructor. This will give this class many more uses.

[franticticktick]

Hi @jzheaux, thanks for your feedback. There are several points that need to be discussed. We can add a static method, for example denyAll, and return a static final instance:

public static <C> SingleResultAuthorizationManager<C> denyAll() {
   return DENY_MANAGER;
}

This is only possible if the SingleResultAuthorizationManager instance has a raw type:

private static final SingleResultAuthorizationManager DENY_MANAGER = new SingleResultAuthorizationManager<>(new AuthorizationDecision(false));

Generics are not available in a static context, which forces us to use a raw type. I'm not sure if this is the best pattern in this case, @jzheaux what do you think about it?

[jzheaux]

@franticticktick good questions. First, I think it's okay to construct a SingleResultAuthorizationManager each time denyAll() is called. This is conventionally the most type-safe and I'm fine going that route.

However, since the implementation knows that it won't use the type, then it can safely use <?>:

private static final SingleResultAuthorizationManager<?> DENY = new SingleResultAuthorizationManager<>(new AuthorizationDecision(false));

That does require a cast in the static method, but again in practice this isn't a concern since this implementation never uses the type at runtime:

public static <T> SingleResultAuthorizationManager<T> denyAll() {
    return (SingleResultAuthorizationManager<T>) DENY;
}

[franticticktick]

Hey @jzheaux thanks for the feedback. I decided to go with the second solution, although static casting may not be to the liking of clean code fans :)

[jzheaux]

Thanks, @franticticktick! This is now merged into main.