Javascript 如何传递HTML输入文件'；使用AJAX将多个值添加到servlet

我的JSP页面中有一个HTML表单。我现在正在使用这个代码

<form method="post" action="saveToDatabase" enctype="multipart/form-data">
  <input type="file" id="document" name="document" onchange="selectedFiles()" multiple>
  <input type="submit" value="Save to Database" id="saveToDB" name="saveToDB">
  <input type="text" id="salesOrder_hidden" name="salesOrder_hidden" hidden>
  <input type="text" id="nameAdded_hidden" name="nameAdded_hidden" hidden>
  <input type="text" id="packType_hidden" name="packType_hidden" hidden>
  <input type="text" id="docType_hidden" name="docType_hidden" hidden>
  <input type="checkbox" id="v2500_hidden" name="v2500_hidden" value="V2500-A5" hidden="true">
  <input type="checkbox" id="7b_hidden" name="7b_hidden" value="CFM56-7B" hidden>
  <input type="checkbox" id="5c_hidden" name="5c_hidden" value="CFM56-5C" hidden>
  <input type="checkbox" id="3_hidden" name="3_hidden" value="CFM56-3" hidden>
</form>

$("#uploadBtn").on("click", function() {
  $.ajax({
    type: "POST",
    encType: "multipart/form-data",
    url: "UploadFile",
    cache: false,
    processData: false,
    contentType: false,
    data: new FormData($("#sampleUploadFrm")[0]),
    success: function(msg) {
      var response = JSON.parse(msg);
      var status = response.status;
      if (status == 1) {
        alert("File has been uploaded successfully");
      } else {
        alert("Couldn't upload file");
      }
    },
    error: function(msg) {
      alert("Couldn't upload file");
    }
  });
});