ResponseText未定义并将json作为[object Object]

Question

好的，我试图在ajax的回调函数中从servlet获取json。但我使用了警报，它给了我[object Object]。当我检查recponse文本时，它是未定义的。我不明白我的意思是servlet上的代码似乎很好我不知道是什么问题？谢谢你的帮助。

我的ajax

$.ajax({
            type: 'POST',
            url: 'OtherServ',
            data: {"frameID": jsonString},
            dataType : "json",
            success :function(json,jqXHR){
                //You can also use html with hidden form
                alert(json);
                    console.log("In Ajax" +json);
                   var form = $('<form></form>').attr('action','displayform.jsp');
                   $(form).attr('method','POST');
                   var ele = $('<input type="text">').attr('name','complete_json');  
                   $(ele).val(json); 
                   $(ele).appendTo($(form));
                   $(form).appendTo('body');
                   $(form).submit();
            } ,
            error: function (jqXHR, exception) {
                var msg = '';
                if (jqXHR.status === 0) {
                    msg = 'Not connect.\n Verify Network.';
                } else if (jqXHR.status == 404) {
                    msg = 'Requested page not found. [404]';
                } else if (jqXHR.status == 500) {
                    msg = 'Internal Server Error [500].';
                } else if (exception === 'parsererror') {
                    msg = 'Requested JSON parse failed.';
                } else if (exception === 'timeout') {
                    msg = 'Time out error.';
                } else if (exception === 'abort') {
                    msg = 'Ajax request aborted.';
                } else {
                    msg = 'Uncaught Error.\n' + jqXHR.responseText;
                }
                alert(msg);
            }  
       });

这是我的servlet代码

response.setContentType("application/json");
        String complete_json = new Gson().toJson(list);
        System.out.println("");
        System.out.println("Complete JSON");
        System.out.println(complete_json);
        response.getWriter().write(complete_json);