DataService.obtain().http(HttpApi.USER_TEST,Action.HTTP_GET)
        .exec(new DataCallback() {
            @Override
            public void onResult(int state, Clause clause, Object data) {
                //success result
            }

            @Override
            public void onError(int state, Clause clause) {
                //failed
                String msg = clause.getMsg();
                //You can get error msg by clause.
            }
        });