Thursday, January 12, 2017

Re: GWT Client for App Engine Endpoints

The hitch seems to be getting the GWT compiler to find the API Java code generated by the annotation processor. That  generated API code is not under the project/html/src/ tree (html=GWT), but rather under the project/backend/build/generated-source/endpoints/java/ tree (eg. java/com/blue_green_group/gdxendpoints/backend/endpointsApi/ ). Failure of the GWT compiler to find the generated API code results in eg.
...html/src/com/blue_green_group/gdxendpoints/backend/api/gwt/services/endpointsApi/shared/ error: cannot find symbol
public enum EndpointsApiAuthScope implements AuthScope {
:   class AuthScope
: interface EndpointsApi
...html/src/com/blue_green_group/gdxendpoints/backend/api/gwt/services/endpointsApi/shared/ error: method does not override or implement a method from a supertype

Possibly the GWT compiler is not looking for the source code in that path, even though I tried adding project/backend/build/generated-source to eg. (which fails because it's not a subdir of the GWT html/ module dir). Possibly because the generated API code is generated by the annotation processors only after the GWT compiles (though it's still in place when starting superdev after the last Android/backend build). Possibly both.

I could have the build process copy the generated API code from the backend module to a src/ dir under the html (GWT) module, but the Endoints pattern is for that code to be shared from a single source dir, not copied to other modules. But maybe that's the only way if GWT cannot share code from a dir outside the GWT module's tree.

On Wednesday, January 11, 2017 at 7:28:56 PM UTC-5, Matthew Rubenstein wrote:
Well, I am making an async HTTP request using the GWT RequestBuilder API, as illustrated in the code snippet in my previous message. RestyGWT might offer better management of requests than my basic RequestBuilder code.

But what that doesn't do is allow me to call the API from GWT code, as I do in my Android AsyncTask:
{ resultDataStr = endpointsApiService.sayHi(name).execute().getData(); }
catch(IOException e)
{ return e.getMessage(); }

I can recode EndpointsApiService.sayHi(String) elsewhere in my code, change its name, and otherwise change both the API and its implementation - as Java. But in the GWT Endpoints client I have to separately maintain the REST URL strings. There are old (broken) tools like Google's apis-client-generator (generate_library) tool that supposedly generate GWT code from the Java API code (annotated). Are there any that actually work, so "just code in Java" gets maintainable Endpoints in GWT?

On Wednesday, January 11, 2017 at 4:39:15 PM UTC-5, Paul Mazzuca wrote:
GAE Endpoints makes available REST EndPoints for your various clients.  If GWT is being used in your client, then you need to make an HTTP request from that client in order to communicate with GAE Endpoints.   So the question is how do you create an HTTP async request from a GWT client?

You could create a HTTP request using the GWT RequestBuilder API, which allows you to create a request from the ground up.  Or, you could use a higher level abstraction like RestyGWT which will do a lot of the heavy lifting for you.  I generally stick to RestyGWT for my REST API requests from a GWT client.  I would read through the documentation of RestyGWT and see if that is a good fit. 

On Wednesday, January 11, 2017 at 11:24:00 AM UTC-8, Matthew Rubenstein wrote:
I currently have the project's GWT module send data to the backend API
// Build API request URL.
backendMethodURLStr= "
endpointRequestURLStr = backendMethodURLStr + "/" + URL.encode(dataStr);

// Ping Endpoint with value REST request.
RequestBuilder builder = new RequestBuilder(RequestBuilder.POST, endpointRequestURLStr);
HttpRequestCallback httpReqClbk = new HttpRequestCallback();
{ builder.sendRequest(null, httpReqClbk); }
catch(RequestException exception)
{ httpReqClbk.onError(null, exception); }


class HttpRequestCallback implements RequestCallback
    public void onResponseReceived(Request request, Response response)
        String responseStr = response.getText();
"HtmlLauncher.onSuccess() response:\n", responseStr);

// Parse data field from JSON response object.
        JSONValue responseJSONVal = JSONParser.parseStrict(responseStr);

So the backendMethodURLStr must be maintained to represent the Endpoints API. Are you saying RestyGWT can be used instead of a crude request string + RequestBuilder, with RestyGWT referencing the shared API that only has to be mainained in one place in the project? Ie. RestyGWT will automatically (after its configured by my code) to reference the class EndpointsApi that's generated by the Endpoints @Api and @ApiMethod annotations.

On Wednesday, January 11, 2017 at 11:59:44 AM UTC-5, Michael Joyner wrote:

I don't know how much it will help, but RestyGWT could be used for the GWT client to access JSON data via a predefined and share-able json rest interface definition.

Then you could use the builts, (a bit manaully), of libGDX net to to http/json calls to the end point.

The end point I would think would need to be a separate project, just use a predefined endpoint API in your clients to access it as a 3rd party service.

On 01/11/2017 10:12 AM, Matthew Rubenstein wrote:
Hello. I'm trying to add a Google Endpoints client to a LibGDX project. Adding one to the GWT module is causing me a lot of problems. Is there a demo GWT project that includes an Endpoints client, deployable to Google App Engine? A project I can open in Android Studio, so either a Gradle project or a (working) Eclipse project that can be imported by AS?

The LibGDX project setup application generates as an Android Studio Gradle project, like this game demo:

including Android, desktop, GWT ("html" module) and even Ios modules. The platform-nonspecific code (most of the clients application code) is implemented in the "core" module. I've added a simple HTTP XML client to a LigGDX GWT module. But it's not really an Endpoints client; it doesn't share the API from the rest of the project as an API, just as a component of a URL string. Is there a direct way to add an Endpoints client to that GWT module that can share the API with the backend and the other client modules? I'd rather not tack on yet another programming environment in a Javascript phase (ie. JsInterop) after GWT just to add the Endpoints client to what is otherwise a Java project. Thanks for your insights.


FWIW, I tried to get help in the Google App Engine group:

But the "Cloud Platform Support" guidance sent me into days of trying various GWT tutorials and demos all of which are broken. My final attempt was the GWT Project's "Build a GWT app" whose sample project executed but rendered a client webpage with no UI widgets.
"Deploy to GAE / Set up a project (without Eclipse)":

"Alternatively, If you would like to skip the Build a Sample GWT Application tutorial, then download and unzip this file."

BTW like all of the GWT instructional projects documentation I tried, that one's link is broken as its target project has been archived. But the file is still available from:

I edited the tutorial project's various config files according to the tutorial's instructions, and fixed some defects not mentioned in the instructions (like increasing the javac heap size to 512M, and adding <threadsafe>true</threadsafe> to appengine-web.xml , and removing old lib/ JARs that have substitute JARs downloaded by Ant, etc). Only to find the project launches in a browser in ant devmode but the browser app fails to include any actual UI widgets.


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