Package dev.gmitch215.bytebox.concurrent

Class Future<T extends org.teavm.jso.JSObject>

java.lang.Object
dev.gmitch215.bytebox.concurrent.Future<T>
Type Parameters:
T - the value type
public final class Future<T extends org.teavm.jso.JSObject> extends Object
A value that is not here yet, backed by a JavaScript promise.

java.util.concurrent.Future and CompletableFuture exist on this platform (bytebox supplies them, because the class library does not), but they have no pool behind them and know nothing about promises. This is the type to use when the work is a JavaScript promise: it carries the part of that API which means something here, over the promise the runtime already understands.

Most code does not need it. A binding call blocks and returns a value, which is more direct than a future and costs the same. Reach for this to hold work open past a handler's return, to start several operations before waiting on any of them, or to hand a promise back to JavaScript. 

 Future<Response> primary = Async.supply(() -> fetchPrimary(env));
 Future<Response> backup = Async.supply(() -> fetchBackup(env));
 ctx.waitUntil(audit(env).promise());
 return primary.orElseGet(backup::join);
Since:
1.0.0

  • Method Summary

    Modifier and Type
    Method
    Description
    static <T extends org.teavm.jso.JSObject>
    Future<T>
    completed(T value)
    A future that is already done.
    static <T extends org.teavm.jso.JSObject>
    Future<T>
    failed(Throwable failure)
    A future that has already failed.
    T
    join()
    Waits for the value.
    <R extends org.teavm.jso.JSObject>
    Future<R>
    map(Function<T,R> mapper)
    Transforms the value once it arrives, on a fiber of its own.
    static <T extends org.teavm.jso.JSObject>
    Future<T>
    of(org.teavm.jso.core.JSPromise<T> promise)
    Adopts an existing promise.
    T
    orElse(T fallback)
    Waits for the value, answering a fallback if the future failed.
    T
    orElseGet(Supplier<T> fallback)
    Waits for the value, calling a supplier if the future failed.
    org.teavm.jso.core.JSPromise<T>
    promise()
    Returns the underlying promise, to hand to JavaScript or to ctx.waitUntil.
    Future<T>
    recover(Function<Throwable,T> recovery)
    Handles a failure without unwinding.
    <R extends org.teavm.jso.JSObject>
    Future<R>
    then(Function<T,Future<R>> next)
    Chains another asynchronous step after this one.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • of

      public static <T extends org.teavm.jso.JSObject> Future<T> of(org.teavm.jso.core.JSPromise<T> promise)
      Adopts an existing promise.
      Type Parameters:
      T - the value type
      Parameters:
      promise - the promise
      Returns:
      a future over it

    • completed

      public static <T extends org.teavm.jso.JSObject> Future<T> completed(T value)
      A future that is already done.
      Type Parameters:
      T - the value type
      Parameters:
      value - the value
      Returns:
      the completed future

    • failed

      public static <T extends org.teavm.jso.JSObject> Future<T> failed(Throwable failure)
      A future that has already failed.
      Type Parameters:
      T - the value type
      Parameters:
      failure - the failure
      Returns:
      the failed future

    • promise

      public org.teavm.jso.core.JSPromise<T> promise()
      Returns the underlying promise, to hand to JavaScript or to ctx.waitUntil.
      Returns:
      the underlying promise, to hand to JavaScript or to ctx.waitUntil

    • join

      public T join()
      Waits for the value.

      Suspends the calling fiber, and rethrows whatever the future failed with.

      Returns:
      the value

    • orElse

      public T orElse(T fallback)
      Waits for the value, answering a fallback if the future failed.
      Parameters:
      fallback - the value to use on failure
      Returns:
      the value, or the fallback

    • orElseGet

      public T orElseGet(Supplier<T> fallback)
      Waits for the value, calling a supplier if the future failed.
      Parameters:
      fallback - produces the value to use on failure
      Returns:
      the value, or what the fallback produced

    • map

      public <R extends org.teavm.jso.JSObject> Future<R> map(Function<T,R> mapper)
      Transforms the value once it arrives, on a fiber of its own.
      Type Parameters:
      R - the new value type
      Parameters:
      mapper - the transformation
      Returns:
      a future for the transformed value

    • then

      public <R extends org.teavm.jso.JSObject> Future<R> then(Function<T,Future<R>> next)
      Chains another asynchronous step after this one.
      Type Parameters:
      R - the new value type
      Parameters:
      next - produces the next future
      Returns:
      a future for the chained result

    • recover

      public Future<T> recover(Function<Throwable,T> recovery)
      Handles a failure without unwinding.
      Parameters:
      recovery - produces a replacement value from the failure
      Returns:
      a future that does not fail