Hi people I need to work with a java api. I'm storing info in a remote store and also in memory. Th...

# announcements

[Wesley Acheson]

Hi people I need to work with a java api. I'm storing info in a remote store and also in memory. The interface for the remote store is that it returns a Mono of the value, but if its not found it returns a Mono with the value null. I'm trying to get the in memory implementation to do the same.

override fun load(id: String): Mono<StoredRequest?> {
        val storedRequest: StoredRequest? = memory[id]
        return Mono.just(null);
    }

However it doesn't allow me to return a Mono of null here or even return the value from the backing map.

As far as I understand the method signature I've given a null should be allowed.

Is there any way to force the java like behaviour?

[tddmonkey]

er…. I didn’t think it was possible to create a Mono with a null value. It should be an empty Mono instead

[Wesley Acheson]

Well in my tests against redis it prints null, (which I assume is not the string null)

val something = repository.load("Not found").block()
        println(something)

[tddmonkey]

Ah - you get null there from an empty mono

[tddmonkey]

So just change your code above to be Mono.empty()

[Wesley Acheson]

override fun load(id: String): Mono<StoredRequest?> {
    val storedRequest: StoredRequest? = memory[id]
    return if (storedRequest != null) Mono.just(storedRequest) else Mono.empty()
}

Works thank you. I think I should be able to use let there but I'm making a hash of it. (no pun intended)

[Wesley Acheson]

override fun load(id: String) = memory[id]?.let { Mono.just(it) }?: Mono.empty()

[tddmonkey]

Ah, if you want that you can just do Mono.justOrEmpty(nullableValue)