SLING-10502 - lazy loading helpers

[bdelacretaz]

This is an initial implementation with a LazyLoadingFieldand LazyLoadingMap that should help build GraphQL result sets with lazy loading values.

[raducotescu]

I agree with all the observations that @jsedding made. There's no need to synchronize the LazyLoadingMap if it extends HashMap. Leave the synchronization to the caller - they can always wrap it in a Collections#synchronizedMap, or extend ConcurrentHashMap.

[bdelacretaz]

Thank you for the detailed review, all good suggestions! Of course, HashMap not being synchronized it doesn't make sense to make the LazyLoadingMap thread safe, I have removed all synchronization in that class.

I think I have implemented all other suggestions, please cross-check.

[jsedding]

LGTM!

[raducotescu]

Would it be too expensive to obey the Map contract in this case?

[bdelacretaz]

It's hard to say - I will make that optional, adding an Options object to the class constructor.

[bdelacretaz]

Committed that, using class methods to set options instead.

[raducotescu]

I think this should be logged on debug - I assume that with GraphQL in Sling catching on, we'll have a lot of LazyLoadingMaps.

[bdelacretaz]

+1 I'll do that

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities
0 Security Hotspots
3 Code Smells

98.9% Coverage
0.0% Duplication

[jsedding]

@bdelacretaz I think you meant to return super.remove(key) here if computeValueOnRemove is true. How about this?

Supplier<T> supplier = suppliers.remove(key);
if (supplier != null) {
    super.remove(key); // this should be unnecessary, otherwise I believe it would be a bug?!
    return computeValueOnRemove ? supplier.get() : null;
} else {
    return super.remove(key);    
}

[bdelacretaz]

Indeed, both the tests and the code were wrong!

Good idea to use the Supplier in this way, I have committed a slightly different fix that sets the Stats and that always returns null unless computeValueOnRemove is set - I think that's less confusing. 4cce079

[jsedding]

👍 looks good to me