Integration with Guava ListenableFuture.

Coroutine builders:

Name Result Scope Description
future ListenableFuture CoroutineScope Returns a single value with the future result

Extension functions:

Name Description
ListenableFuture.await Awaits for completion of the future (cancellable)
Deferred.asListenableFuture Converts a deferred value to the future

Example

Given the following functions defined in some Java API based on Guava:

public ListenableFuture<Image> loadImageAsync(String name); // starts async image loading
public Image combineImages(Image image1, Image image2); // synchronously combines two images using some algorithm

We can consume this API from Kotlin coroutine to load two images and combine then asynchronously. The resulting function returns ListenableFuture<Image> for ease of use back from Guava-based Java code.

fun combineImagesAsync(name1: String, name2: String): ListenableFuture<Image> = future {
    val future1 = loadImageAsync(name1) // start loading first image
    val future2 = loadImageAsync(name2) // start loading second image
    combineImages(future1.await(), future2.await()) // wait for both, combine, and return result
}

Note that this module should be used only for integration with existing Java APIs based on ListenableFuture. Writing pure-Kotlin code that uses ListenableFuture is highly not recommended, since the resulting APIs based on the futures are quite error-prone. See the discussion on Asynchronous Programming Styles for details on general problems pertaining to any future-based API and keep in mind that ListenableFuture exposes a blocking method get that makes it especially bad choice for coroutine-based Kotlin code.

Packages

kotlinx.coroutines.guava

Index

All Types