How to get String from Mono in reactive java

Question

I have a method which accepts Mono as a param. All I want is to get the actual String from it. Googled but didn\'t find answer except calling block() over Mono object but it

Answer 1

Getting a String from a Mono without a blocking call isn't easy, it's impossible. By definition. If the String isn't available yet (which Mono allows), you can't get it except by waiting until it comes in and that's exactly what blocking is.

Instead of "getting a String" you subscribe to the Mono and the Subscriber you pass will get the String when it becomes available (maybe immediately). E.g.

myMono.subscribe(
  value -> Console.out.println(value), 
  error -> error.printStackTrace(), 
  () -> Console.out.println("completed without a value")
)

will print the value or error produced by myMono (type of value is String, type of error is Throwable). At https://projectreactor.io/docs/core/release/api/reactor/core/publisher/Mono.html you can see other variants of subscribe too.