Wednesday, September 6, 2017

Re: Emulating CompletableFuture with Promise

I decided to package this up in a standalone library so it can be used until such time that it makes it into a GWT release.


On Monday, September 5, 2016 at 4:47:10 AM UTC-4, Andrei Korzhevskii wrote:
I guess you need to super-source this class so the gwt compiler could use it.

You can take a look at my initial CompletableFuture implementation here:


Feel free to use it but note that I haven't tested it properly yet.



On Monday, September 5, 2016 at 3:28:27 AM UTC+3, Ian Preston wrote:
I'm trying to emulate CompletableFuture by backing directly onto Promise, but when compiling it gives this error: 
"No source code is available for type java.util.concurrent.CompletableFuture<T>"
(it finds other JRE classes I've replaced fine)

My source I'm including is below. Am I doing anything illegal?
********************************************
package java.util.concurrent;

import com.google.gwt.user.client.*;
import jsinterop.annotations.*;

import java.util.function.*;

@JsType(isNative=true, name = "Promise", namespace = JsPackage.GLOBAL)
public class CompletableFuture<T> implements CompletionStage<T> {

    @JsMethod(name = "then")
    public native <U> CompletableFuture<U> thenApply(Function<? super T,? extends U> fn);

    @JsMethod(name = "then")
    public native CompletableFuture<Void> thenAccept(Consumer<? super T> action);

    @JsMethod(name = "then")
    public native <U> CompletableFuture<U> thenCompose(Function<? super T, ? extends CompletionStage<U>> fn);

    @JsMethod(name = "reject")
    public native boolean completeExceptionally(Throwable ex);

    @JsMethod(name = "resolve")
    public native boolean complete(T value);

    @JsMethod(name = "resolve")
    public static native <U> CompletableFuture<U> completedFuture(U value);

    @JsOverlay
    public T get() throws InterruptedException, ExecutionException {
        Window.alert("Calling synchronous get() on CompletableFuture is not possible in Javascript!");
        throw new IllegalStateException("Unimplemented!");
    }
}

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