DynamicForm automatically fetchs data with RestDataSource

Hi everyone,

I face a problem as following:
1.I created a button which will open a layout.
2.In the layout, I created a DynamicForm with some items and set MyDataSource for the form.
3.I created MyDataSource by extending RestDataSource
4.Whenever I click the button to open the layout, there is a fetch request to server.

I think the problem is MyRestDataSource. Because if I remove setDataSource(myDataSource) then there is no unexpected request.
Please help me to figure out the problem.

I use SmartGWT 5.0p.