Mocking logout throws an error

Hi i have the below to methods one for logging out and the other is internally called to clear cookies. I first started with mocking the second method to delete cookie. I am getting an exception and I am not sure how to mock the first method. I referred this code from DZone.

public class Service
{
    @RequestMapping(value = "/logout", method = RequestMethod.POST)
    public String logout(HttpServletRequest request,HttpServletResponse response) {
        HttpSession session = request.getSession(true);
    session.setAttribute("sessionid","id");
    Cookie first=new Cookie("name","Mycookie");
    response.addCookie(first);
        if (request.isRequestedSessionIdValid() && session != null) {
        session.invalidate();
        }
        HttpServletResponse sessionRes=handle(request,response);
    return sessionRes;
        }


    public HttpServletResponse handle(HttpServletRequest request, HttpServletResponse response)
    {
        Cookie[] cookies = request.getCookies();
        if(cookies!=null || cookies.length!=0)
        {
            for(Cookie cookie:cookies)
            {
                cookie.setMaxAge(0);
                cookie.setValue(null);
                cookie.setPath("/");
                response.addCookie(cookie);
            }
            response.addHeader("message", "No cookies found");
        }
        return response;
    }
}

Here is my test case for handle method. It returns me Null Pointer exception. I don't know where i went wrong. And please do help me writing mockito test case for logout function also.

@RunWith(MockitoJUnitRunner.class)
public class LogoutTest {
    @InjectMocks
    Service service;

    @Mock
    Cookie cookie;
    @Mock
    HttpServletRequest request;
    @Mock
    HttpServletResponse response;

    @Test
    public void TestHandle()
    {
        cookie=new Cookie("fname","ram");
        response.addCookie(cookie);
        when(service.handle(request,response)).thenReturn(response);
        assertEquals("No cookies found",response);
    }

}