SpringMVC+ajaxfileupload文件上传返回json下载？

$.ajaxFileUpload
            (
                {
                    url:'upload1.jhtml',
                    secureuri:false,
                    fileElementId:'uploadFile',
                    dataType: 'json',
                    success: function (data, status)
                    {
                        alert(data);
                        if(data.status==1){
                            alert(data.result);
                        }else{
                            alert("【提交失败！】");
                        }
                    },
                    error: function (data, status, e)
                    {
                        alert("【服务器异常，请连续管理员！】"+e);
                    }
                }
            );

为什么在IE下面会提示下载文件呢？在IE情况下，不支持application/json
在后台spring mvc代码中
response.setContentType("text/javascript;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.println(obj);
改成
response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.println(obj);

将ajaxFileUpload中的dataType: 'json' 改成dataType: 'text'