Shortcut methods

Learn the different shortcuts reducing verbosity.

The Mutiny API is decomposed around the idea of groups, each group handling a specific event. However, to avoid verbosity, Mutiny also exposes shortcuts for the most used methods. Be aware that these shorts, while making the code shorter, may harm the readability and understandability.

To peek at items, you can use the invoke method:

Multi<String> multi = Multi.createFrom().items("a", "b", "c");
multi.invoke(item -> System.out.println("Received item " + item));

invoke is a shortcut for onItem().invoke(…​).

Mutiny also provides the call method for executing an action returning a Uni. This is useful to execute an asynchronous action without modifying incoming item: -> executeAnAsyncAction(item));

call is a shortcut for onItem().call(…​).

The following table lists the available shortcuts available by the Uni class:

Shortcut Equivalent → y)

uni.onItem().transform(x → y)

uni.flatMap(x → uni2)

uni.onItem().transformToUni(x → uni2)

uni.chain(x → uni2)

uni.onItem().transformToUni(x → uni2)

uni.then(() → uni2)

uni.onItem().transformToUni(ignored → uni2)

uni.invoke(x → System.out.println(x))

uni.onItem().invoke(x → System.out.println(x)) → uni2)

uni.onItem().call(x → uni2)

uni.eventually(() → System.out.println("eventually"))

uni.onItemOrFailure().invoke((ignoredItem, ignoredException) → System.out.println("eventually"))

uni.eventually(() → uni2)

uni.onItemOrFailure().call((ignoredItem, ignoredException) → uni2)


uni.onItem().transform(ignored → x)


uni.onItem().transformToUni(ignored → uni2)