CODEWITHSUNDEEP
javaproject-reactorcaffeine-cache
A Jar of Clay
A Jar of Clay

Reputation: 6308

How to store a Mono error in Async Caffeine Cache?

AsyncLoadingCache<String, String> cache = Caffeine.newBuilder().buildAsync(
  (String k, Executor e) ->
    doThingReturnsMono()
      .subscribeOn(Schedulers.fromExecutor(e))
      .toFuture()
);

cache.put("fail", Mono.error<String>(new RuntimeException()).toFuture());
cache.put("success", Mono.just("success").toFuture());

System.err.println(cache.asMap().getKeys()); // Prints ["success"]

How can we put a Mono.error into an AsyncLoadingCache?

Upvotes: 0

Views: 92

Answers (1)

A Jar of Clay
A Jar of Clay

Reputation: 6308

The async cache handles values coming in asynchronously, it does not store raw Futures/Monos. It instead stores the underlying data, in this case a String.

A wrapper type is needed in this case:

class MaybeString {
  // ...
  String str;
  boolean isError;
}

AsyncLoadingCache<String, String> cache = Caffeine.newBuilder().buildAsync(
  (MaybeString k, Executor e) ->
    doThingReturnsMono()
      .subscribeOn(Schedulers.fromExecutor(e))
      .toFuture()
);

cache.put("fail", Mono.just(new MaybeString("", true)).toFuture());
cache.put("success", Mono.just(new MaybeString("success", false)).toFuture());

System.err.println(cache.asMap().getKeys()); // Prints ["fail", "success"]

Upvotes: 2

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