如何通过 JSP 代码将隐藏字段(Javascript）插入 XML

我正在尝试将Javascript隐藏字段中的数据插入XML中，但是，只有"null"出现。我已经声明了变量，但似乎它无法捕获隐藏字段。我处于智慧的尽头，我希望我的问题能够得到解决。

**<<-----I use session to pass the value to the XML page----->>**

<%
String X = (String)session.getAttribute("X");
    String Y = (String)session.getAttribute("Y");
    String W = (String)session.getAttribute("W");
    String H = (String)session.getAttribute("H");       
session.setAttribute("X",X);
session.setAttribute("Y",Y);
session.setAttribute("W",W);
session.setAttribute("H",H);
%>

**<<------Snippet of Javascript codes------->>**
function moveIt(){ 
if (!moveEnabled||!MovableItem) return;
// display info during testing
X = MovableItem.offsetLeft;
Y = MovableItem.offsetTop;
W = MovableItem.offsetWidth;
H = MovableItem.offsetHeight;
 ==Some codes here==
  document.getElementById('X').value = X;     
  document.getElementById('Y').value = Y;
  document.getElementById('W').value = W;
  document.getElementById('H').value = H;  

}

**<<-----JSP codes that I need to pass the values onto an XML----->>**
 <form name='form1' action='UpdateXML.jsp' method='post'>
<input type='hidden' name=source value="<%=src%>" />
<input type='hidden' id="X" name="X" value="<%=X%>"/>
<input type='hidden' id="Y" name="Y" value="<%=Y%>"/>
<input type='hidden' id="W" name="W" value="<%=W%>"/>
<input type='hidden' id="H" name="H" value="<%=H%>"/> 
<button type="button" onclick="window.location.href='editcompany.jsp'">Back!</button>
<button type="submit">Insert Into XML!</button>
</form>

我需要将隐藏字段（数据）插入到 XML 中。我试过了，但它显示为"空"。有没有人可以帮助我解决这个问题？谢谢一堆！