create and return gwt widget from java code

Question

I am new to GWT and I need to reslove this problem. I need to create a widget with gwt-links. To make it happened, I need to fetch some data from an ontology, and then based on the result, create the graph. The problem is that, when I mix java code with gwt code it doesn't want to compile.

The question is, how do I create a widged explained above that will be placed in a http page?

The code looks like this now :

public class Example1 {

    @Override
    public void draw() {

        // Create the elements

        String ontology = Ontology.get(1);

        Widget labelHello = new BoxLabel(ontology);
        controller.addWidget(labelHello,25,115);


        // Add DnD logic
        PickupDragController dragController = new PickupDragController(controller.getView(), true);
        dragController.makeDraggable(labelHello);


    }


    public Widget asWidget() {
        return controller.getView();
    }

}

the Ontology.get() doesn't want to compile.

Could you provide a stack trace ?

Olivier Tonglet
– Olivier Tonglet

2013-09-26 06:47:01 +00:00
Commented Sep 26, 2013 at 6:47 — Olivier Tonglet
– Olivier Tonglet, Commented Sep 26, 2013 at 6:47

Spiff · Accepted Answer · 2013-09-26 06:28:10Z

1

GWT can't compile just any java code.

These are the packages that are emulated by GWT: pls read

The code that can't be translated to javascript, (the stuff that is not emulated) you must handle on the server side.

edited Sep 26, 2013 at 6:28

answered Sep 26, 2013 at 5:49

Spiff

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3 Comments

Olivier Tonglet Over a year ago

In most case you can reimplement the code that can't be translated to javascript (i.e. libs like StringUtils) in your client code.

Spiff Over a year ago

Yes you are right. Sometimes it's easier to just move this code if possible on the server side.

Spiff Over a year ago

My guess was that @user2816447 was not aware of the fact that it's not possible to compile any java library to javascript.

Christian Kuetbach · Accepted Answer · 2013-09-26 22:12:42Z

1

GWT projects uses three packages (by default)

com.myapp.client
com.myapp.shared
com.myapp.server

By default everything within the shared and client package will be compiled to JavaScript. Every Class, which is imported into a Class, which is inside the shared and client package must be:

emulated by GWT
Compilable to GWT (and inside the client or shared package)
Compilable to GWT (and the package must be whitelists in *.gwt.xml)

Uf you code ISolver can be compiled to JavaScript you will have to create a module.gwt.xml and inheritt your project from this module. This may enable the GWT-compiler to compile ISolver (and its implementation) to JavaScript.

If your code can't be compiled to GWT you will have to write a remote-service to make the calculation.

answered Sep 26, 2013 at 22:12

Christian Kuetbach

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2 Comments

user2816447 Over a year ago

Thank you for the answer. Looks like remote service is the solution. IF it is on the server side, can it return/pass an gwt object ( a widget) to be later translated to javascript and placed on a page?

Christian Kuetbach Over a year ago

No, you should create the Widget at clientside and set the values after you get them from the server. You also can ask the server for the values and create the widget in the success-handler.

user2816447 · Accepted Answer · 2013-09-26 21:11:28Z

0

I don't really want to compile the code to javascript. All i want to do is to create a GWT widget ( which is a graph).

To create the widget, I need to do some calculations and repository fetch. I dont want to translate it( repository fetching), I just need to use it in order to create the model of the graph.

Basically, this is something I want to do:

String l = Repository.getLabel(); // Some advanced calculations that use many JavaSE classes;
GWTWidget widget = new GWTWidget(l);  // widget, that will be displayed on a page.

but when I put something in method onModuleLoad it doesn't compile.

This is probably a simple question, but I'm not really related with GWT and I'm forced to remake someone's work.

 public void onModuleLoad() {
        System.out.println("tes");
        VerticalPanel mainPanel = new VerticalPanel();
        RootPanel.get().add(mainPanel);

        //
        ISolver solver = null;
        System.out.println("TEST2");
    }

ERROR: Line 53: No source code is available for type pr.ISolver; did you forget to inherit a required module?
  ERROR: Unable to find type 'client.Link'
    ERROR: Hint: Previous compiler errors may have made this type unavailable

and other lines sthat start with " No source code..".

ISolver is an interface, but I dont want to translate it. I want to use it for calculations.

edited Sep 26, 2013 at 21:11

answered Sep 26, 2013 at 17:47

user2816447

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3 Comments

Spiff Over a year ago

pls post the exception

Spiff Over a year ago

The thing is that Java is translated to Javascript, that's how GWT works, that's why the browser executes a GWT app without a plugin.

Christian Kuetbach Over a year ago

But if you add this to the onModuleLoad() you are compiling it to JavaScript.

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