Completable Future in GWT 2.8-rc1

[zakaria amine]

Hello, 

I tried using CompletableFuture in my application, and I got the famous error :

 [ERROR] Line 92: No source code is available for type java.util.concurrent.CompletableFuture<T>; did you forget to inherit a required module?

I suppose CompletableFuture is not emulated, right ? are there other alternatives ? 

[Ignacio Baca Moreno-Torres]

This is much better than promises https://github.com/intendia-oss/rxjava-gwt ;) specially combined with https://github.com/intendia-oss/autorest-gwt and https://github.com/intendia-oss/rxgwt.

[Jens]

I suppose CompletableFuture is not emulated, right ? are there other alternatives ? 

Yes CompletableFuture emulation is still work in progress and not available in GWT 2.8.0.

-- J.

[zakaria amine]

Thanks for the info. rxjava-gwt sounds promising, it does add some complexity though...I will do with Promise for now.

[Ignacio Baca Moreno-Torres]

I'm curious... what problem are you trying to solve using promises (requests, events, presenter logic...)?

[Pablo Nussembaum]

Hi Zakaria,
Do you have any example of how do you use Promises from GWT?

On 23/08/16 06:07, zakaria amine wrote:

Thanks for the info. rxjava-gwt sounds promising, it does add some complexity though...I will do with Promise for now.

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[zakaria amine]

I am working with native XMLHTTPRequest. I am trying to write a utility that simplifies the asynchornous calls, and that I can use from my applications to call Rest Services. 

[zakaria amine]

Hi Bauna,

here is what I did so far, and it is working fine for now: 

@JsType(isNative=true, namespace=GLOBAL)

public class Promise {

@JsConstructor

public Promise(PromiseExecutor executor){

}

//catch is a keyword in java

 @JsMethod(name = "catch")

public native Promise onException(Function reject);

public native Promise then(Function resolve);

}

@JsFunction

@FunctionalInterface

public interface PromiseExecutor {

public void executor(Function resolve, Function reject);

}

@JsFunction

@FunctionalInterface

public interface Function {

public Object call(Object event);

}

//...

Promise promise = new Promise(new PromiseExecutor() {

@Override

public void executor(Function resolve, Function reject) {

//do something 

                                resolve(value);

}

});

//...

promise.then(new Function(){

@Override

public Object call(Object resp) {

                        // Do something with resp, which is your resolved value

return null;

}

  

  

  });

[Ignacio Baca Moreno-Torres]

Looks like a perfect fitting for RxJava, not sure why it add complexity. Promises has no concept of subscription, so requests cannot be canceled, also you will going to need to create a lot of SAM to support generics and lambdas, this is already implemented in RxJava which is pretty mature project used in servers and androids! and now in GWT ;)

This is what can be done in RxJava and you will need lot of code to get there with promises ;)

RxGwt.click(buttonToLoadSomething)
  // this will cancel the previous request… --v …if next click occurs before previous has done
  .switchOnNext(event -> autoRestService.loadZeroOneOrLotOfItems()
    .doOnSubscribe(() -> table.cleanAndShowLoading() /* do this on each new server request */)
    .onErrorResumeNext(err -> { table.stopLoadingAndShowWhy(err); return empty(); }))
  .filter(item -> item.name.startWith("iDontLikeThisOne"))
  .subscribe(item -> table.addRow(item));

I'll encourage to try it out, AutoREST will just guide you to a more uniform API, instead of the RequestBuilder ModelVistor (https://github.com/intendia-oss/autorest-gwt/blob/master/gwt/src/main/java/com/intendia/gwt/autorest/client/RequestResourceBuilder.java) create your own using native XMLHTTPRequest. If you don't prefer Observable is because you haven't used them ;), hehe or not! I' just trying to promote rxjava-gwt.