CODEWITHSUNDEEP
javahttpgwt
malkoto1
malkoto1

Reputation: 435

GWT suddenly stops executing

I have an unusual issue with GWT. I run it with oppening the .html file after compiling the project, on my browser. It is running fine until the following lines of code appear:

public static ClickHandler addBoardButtonHandler(final String name) {
    return new ClickHandler(){

        @Override
        public void onClick(ClickEvent event) {
            Window.alert("We will retrieve them!"); //this line runs
            String boardSTickets = getBoardSTickets(name); // this too
            Window.alert("We got tickets!"); // the code is never executing this line
            String boardSSwimlanes = getBoardSSwimlanes(name);
            Window.alert("We got swimlanes!");
            KanbanizerClient.showSingleBoard(boardSTickets, boardSSwimlanes);
        }

    };
}

This method is called by this other method: 

private static Button addBoardButton(String name) {
    Button button = new Button(name);
    button.addClickHandler(HandlerManager.addBoardButtonHandler(name));
    return button;
}

Which is also running properly. Here is the getBoardSTickets() method:

protected static String getBoardSTickets(String name) {
    final List<String> ticketsJSON = new LinkedList<String>();  
    try {
            Request request = Builder.createBuilder(RequestBuilder.GET, "http://localhost:8080/Kanbanizer/boards/" + name + "/tickets").sendRequest(null, new RequestCallback(){

                @Override
                public void onResponseReceived(Request request,
                        Response response) {
                    if(response.getStatusCode() == 200){
                        ticketsJSON.add(response.getText());
                    }

                }

                @Override
                public void onError(Request request, Throwable exception) {
                    // TODO Auto-generated method stub

                }

            });
        } catch (RequestException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    return ticketsJSON.get(0);
}

Thank you :)

Upvotes: 1

Views: 124

Answers (1)

appbootup
appbootup

Reputation: 9537

For understanding ajax in GWT context - Please read through "Making Asynchronous Call" section in https://developers.google.com/web-toolkit/doc/latest/tutorial/clientserver

Your programming of getBoardSTickets() as a method that returns string after executing a asynchronous request call is flawed. Do not try to return the result of a asynchronous call in getBoardSTickets().

return ticketsJSON.get(0); gets invoked immediately after sendRequest(). It would throw a exception as ticketsJSON would have zero entries because RequestCallback() would not have completed processing.

Try passing a callback from outside 

protected static String getBoardSTickets(String name,  RequestCallback callback){
      //Code for making request
}

You invocation code should change to 

getBoardSTickets(name, new RequestCallback(){
  //onSuccess and onFailure handling.
} )

The same logic holds true for all methods that invoke a async call to server. You should not program to return a value of the request response from the method.

Upvotes: 2

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