snippets.java

// acquire data source
Flux<Integer> dataSource = Flux.just(1, 2, 3, 4, 5, 6);  

// define pipeline of operations
Flux<Integer> pipeline = dataSource  
        .filter(num -> num % 2 == 0) 
        .map(num -> num + 1);  
  
// execute pipeline
pipeline.subscribe();

// ------------------------------------------------------------
    
Flux<T> dataSource = // get the data source from wherever (e.g. network request body, DB call, method call)

Flux<T> pipeline = dataSource
     .operation1(x -> /* perform work on x */)
     .operation2(y -> /* perform work on y */)
     .operation3(z -> /* perform work on z */);

// ------------------------------------------------------------

Flux<T> dataSource = // get the data source from wherever

Flux<T> pipeline = dataSource
     .operation1(x -> /* perform work on x */)
     .operation2(y -> /* perform work on y */)
     .operation3(z -> /* perform work on z */);
     
/*
 * this will actually execute our pipeline
 * as there's at least one subscriber
 * interested in it
 */
pipeline.subscribe();

// ------------------------------------------------------------

// this is our reactive collection of type UserEntity
Mono<UserEntity> currentUser = loginService.getCurrentLoggedUser();

// let’s operate on our reactive collection
Mono<Boolean> isUserAllowed = currentUser
    .map(UserEntityUtils::convertEntityToModel)
	.filter(UserModelUtils::isUserAdmin)
    .switchIfEmpty(Mono.defer(() -> false))
    .flatmap(userModel -> true);   

return isUserAllowed;