关于fromdata的上传文件问题

 <div class="imgDIv"> 2 <label>上传pdf</label> 3 <input id="fileId" type="file" accept="application/pdf" class="imgPic"/> 4 </div> 

var formData = new FormData();
    var file = $("#fileId")[0].files[0];
    formData.append('file', file);
    $.ajax({
        type:'POST',
        url:Feng.ctxPath + "/catalog/add",
        data:formData,
        dataType: "formData",
        cache: false,
        contentType: false,
        processData:false,
        mimeType:"multipart/form-data",
        success:function(data){
            if(data.code==200){
                layer.msg("保存成功！");
                window.parent.Catalog.table.refresh();
            }else{
                layer.msg(data.msg)
            }
        }
    });