tigermoon/future-converter

Converts between various future types

Future Converter

Converts between various future types, RxJava Observables, Spring 4 ListenableFuture, Java 8 CompletableFuture and Guava ListenableFuture.

Please note that the conversion is not always straightforward. Especially RxObservables are completely different concept than Futures. Nevertheless, the conversion is more or less possible.

I am aware of the following quirks:

• Observable can produce multiple values. When converting to Future, we take the first value
• It is not possible to cancel CompletableFuture if it's blocked.

The project has pretty good test coverage, but testing asynchronous stuff is tricky. If you find any bug, please let me know.

spring-java8

Converts between Spring 4 ListenableFuture and Java 8 CompletableFuture

Import the dependency

<dependency>
    <groupId>net.javacrumbs.future-converter</groupId>
    <artifactId>future-converter-spring-java8</artifactId>
    <version>0.3.0</version>
</dependency>

And then use

import static net.javacrumbs.futureconverter.springjava.FutureConverter.*;

...
CompletableFuture<String> completable = toCompletableFuture(listenable);
...
ListenableFuture<String> listenable = toListenableFuture(completable);

spring-guava

Converts between Spring 4 ListenableFuture and Guava ListenableFuture

Import the dependency

<dependency>
    <groupId>net.javacrumbs.future-converter</groupId>
    <artifactId>future-converter-spring-guava</artifactId>
    <version>0.3.0</version>
</dependency>

And then use

import static net.javacrumbs.futureconverter.springguava.FutureConverter.*;

...
com.google.common.util.concurrent.ListenableFuture<String> guavaListenableFuture
        = toGuavaListenableFuture(springListenableFuture);
...
org.springframework.util.concurrent.ListenableFuture<String> springListenableFuture
        = toSpringListenableFuture(guavaListenableFuture);

java8-guava

Converts between Java 8 CompletableFuture and Guava ListenableFuture

Import the dependency

<dependency>
    <groupId>net.javacrumbs.future-converter</groupId>
    <artifactId>future-converter-java8-guava</artifactId>
    <version>0.3.0</version>
</dependency>

And then use

import static net.javacrumbs.futureconverter.java8guava.FutureConverter.*;

...
ListenableFuture<String> guavaListenableFuture = toListenableFuture(completable);
...
CompletableFuture<String> completable = toCompletableFuture(listenable);;

#RxJava Please note that conversion from/to RxJava Observables is not straightforward.

• When converting Observable to a Future, only one element can be produced by the Observable. If your observable produces multiple values, please limit it using observable.take(1).
• When converting a Future to an Observable, it's not clear what should happen upon unsubscribe. Since version 0.2.2 RxJava support does not cancel the Future, since there is no good place to keep track of the subscriptions (there may be multiple subscriptions for any given Future).
• Converting Observable to a Future registers exactly one subscription which is unsubscribed upon Future cancellation.

rxjava-java8

Converts between RxJava Observables and Java 8 CompletableFuture

Import the dependency

<dependency>
    <groupId>net.javacrumbs.future-converter</groupId>
    <artifactId>future-converter-rxjava-java8</artifactId>
    <version>0.3.0</version>
</dependency>

And then use

import static net.javacrumbs.futureconverter.java8rx.FutureConverter.*;

...
CompletableFuture<String> completable = toCompletableFuture(observable);
...
Observable<String> observable = toObservable(completable);

spring-rxjava

Converts between RxJava Observables and Spring 4 ListenableFuture

Import the dependency

<dependency>
    <groupId>net.javacrumbs.future-converter</groupId>
    <artifactId>future-converter-spring-rxjava</artifactId>
    <version>0.3.0</version>
</dependency>

And then use

import static net.javacrumbs.futureconverter.springrx.FutureConverter.*;

...
ListenableFuture<String> listenable = toListenableFuture(observable);
...
Observable<String> observable = toObservable(listenable);

guava-rxjava

Converts between RxJava Observables and Guava ListenableFuture

Import the dependency

<dependency>
    <groupId>net.javacrumbs.future-converter</groupId>
    <artifactId>future-converter-guava-rxjava</artifactId>
    <version>0.3.0</version>
</dependency>

And then use

import static net.javacrumbs.futureconverter.guavarx.FutureConverter.*;

...
ListenableFuture<String> listenable = toListenableFuture(observable);
...
Observable<String> observable = toObservable(listenable);