Hands-On Reactive Programming in Spring 5

The subscribeOn operator

Another important factor for multithreading in Reactor is through an operator called subscribeOn. In contrast to publishOn, subscribeOn allows you to change the worker on which part of the subscription chain is happening. This operator can be useful when we create a source of the stream from the execution of a function. Usually, such executions take place at subscription time, so a function that provides us with the source of data that executes the .subscribe method is called. For example, let's take a look at the following code sample, which shows how we can supply some information using Mono.fromCallable:

ObjectMapper objectMapper = ...
String json = "{ \"color\" : \"Black\", \"type\" : \"BMW\" }"; Mono.fromCallable(() ...