Question

I’m writing a project in GWT over GAE with SmartGWT.

I’ve got a DB with object, each having a “father” object and “sons”, and I’m using a TreeGrid to represent them. I already have a GWT-RPC service that gets the sons of a given node.

What I need now is to somehow extend the DataSource class s.t when a tree node is opened, I will be able to use my own service to go and fetch it’s sons – and then return them as something the TreeGrid can work with.

I know I’m suppose to override transformRequest and transformResponse, but I have no idea how. Any code sample / explanation will be greatly appreciated!

This is what I have so far – not sure it’s even remotely correct:

              budgetTree.setDataSource(new DataSource() {

            @Override
            protected Object transformRequest(final DSRequest dsRequest) {

              expensesService.getExpensesByYear(2008,
                  new AsyncCallback<ExpenseRecord[]>() {

                    @Override
                    public void onSuccess(ExpenseRecord[] result) {
                      System.out.println("Returned " + result.length + " expense record ");            
                      dsRequest.setAttribute("dsResult", result);
                    }

                    @Override
                    public void onFailure(Throwable caught) {
                      System.out.println("Failed to run query");
                    }

                  });

              return dsRequest;
            }

            @Override
            protected void transformResponse(DSResponse response, DSRequest request,
                Object data) {    
              Record[] recs = request.getAttributeAsRecordArray("dsResult");
              response.setData(recs);
              super.transformResponse(response, request, data);
            }


          });

Answer 1

Since you are performing the actual request yourself , you first need to look at
setDataProtocol(DSProtocol.CLIENTCUSTOM);

Then in both onSuccess and onFailure you would need to call processResponse() which will call transformResponse()

public class MyDatasource extends DataSource{
    public MyDatasource(){
        setDataProtocol(DSProtocol.CLIENTCUSTOM)           
    }

    @Override
    protected Object transformRequest(final DSRequest dsRequest) {

          expensesService.getExpensesByYear(2008,
              new AsyncCallback<ExpenseRecord[]>() {

                @Override
                public void onSuccess(ExpenseRecord[] result) {
                  DSResponse response = new DSResponse();
                  System.out.println("Returned " + result.length + " expense record ");            
                  dsRequest.setAttribute("dsResult", result);
                  Record[] recs = request.getAttributeAsRecordArray("dsResult");
                  response.setData(recs);
                  processResponse(dsRequest.getRequestId(), dsResponse);
                }

                @Override
                public void onFailure(Throwable caught) {
                  DSResponse response = new DSResponse();
                  System.out.println("Failed to run query");
                  processResponse(dsRequest.getRequestId(), dsResponse);
                }

              });

          return dsRequest;
   }

}