为什么即使$.getjson运行正常,警报也不运行?(回调未执行,即使请求与getjson一起工作正常)

我有一段代码,比如:

$.getJSON("http://mysite.org/polls/saveLanguageTest?url=" + escape(window.location.href) + "&callback=?",
              function (data) {
          var serverResponse = data.result;
          console.log(serverResponse);
          alert(serverResponse);
}); 

它可以很好地工作,因为它向我的服务器发出跨域请求,服务器按照我的期望保存数据。不幸的是,即使服务器保存了数据并发送了响应,我还是无法得到任何警报或console.log运行。为什么会这样?服务器端代码是(如果相关的话):

def saveLanguageTest(request):
    callback = request.GET.get('callback', '')

    person = Person(firstName = 'Anonymous',
                    ipAddress = request.META['REMOTE_ADDR'])
    person.save()

    webPage = WebPage(url = request.GET.get('url'))
    webPage.save()

    langTest = LanguageTest(type = 'prepositionTest')
    langTest.person = person
    langTest.webPage = webPage
    langTest.save()

    req ['result'] = 'Your test is saved.'
    response = json.dumps(req)
    response = callback + '(' + response + ');'

    return HttpResponse(response, mimetype = "application/json")

我错过了什么?(我在我的网页和Firebug中都尝试了相同的代码,我总是遇到上面提到的问题。)