public static <T> RestResponse<T> fail() {
        return new RestResponse<T>(-1);
    }
@Test
    public void testFail() {
        Assert.assertFalse(RestResponse.fail().isSuccess());
        Assert.assertEquals("error", RestResponse.fail("error").getMsg());
        Assert.assertEquals("error", RestResponse.fail(500, "error").getMsg());
    }