How to give input as json string to DataSource in smartGwt?

How to give input as json string to DataSource in smartGwt? I am new to smartGwt. I want to create a ListGrid by giving Json string object. How can i do that. If i gave Json file path its working perfectly. But i want to give input as Json String.

Code i Used:

String dummyResponse ="[{\"SystemName\":\"LAVA\",\"email\":\"abc@mail.com
\"}]";
setDataFormat(DSDataFormat.JSON);
setDataURL(dummyResponse );

Please give a solution me as soon as possible... Thanks