正在将用户输入写入XML文件

我正在JSP中处理一个项目。现在，我的程序成功地从XML文件中提取内容并将其输出到div中。我还有一些文本框可以读取用户输入。我试图将XML文件的内容更新为用户在文本框中输入的内容，然后调用Names（）方法将更新后的文件的内容输出到div中（替换旧内容）。但是，我的XML文件没有更新，我不确定如何进行更新。这是我的代码：

<script src ="http://code.jquery.com/jquery-latest.min.js" type="text/javascript"></script> 
 <div id ="nameDiv"></div>
<div id = "nameInput">
  <input type = "text" name = "nameOne"  value = "Enter a Name" onClick = "if(this.value == 'Enter a Name'){this.value = '';}" /> 
 <input type = "text" name="nameTwo"  value = "Enter a Name" onClick = "if(this.value == 'Enter a Name'){this.value = '';}" /> 
  <input type ="text"  name = "nameThree"  value = "Enter a Name" onClick = "if(this.value == 'Enter a Name'){this.value = '';}" /> 
  <input type = "button" name = "btnUpdate" value = "Update Name" /></div> 
<% String name1 = request.getParameter("nameOne");
 String name2 = request.getParameter("nameTwo");
 String name3 = request.getParameter("nameThree");
 File file  = new File("Employees.xml");
 public void updateXML(){
      if(name1 ! = '' || name2 != '' || name3 != ''){
         try{
          DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
          DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
          Document document = documentBuilder.parse(file);
          Node firstNameLine = document.getElementsByTagName("People").item(0);
          Node secNameLine = document.getElementsByTagName("People").item(1);
          Node thirdNameLine = document.getElementsByTagName("People").item(2);
          firstNameLine.setText(name1);
          secNameLine.setText(name2);
          thirdNameLine.setText(name3);
          TransformerFactory transformerFactory = TransformerFactory.newInstance();
          Transformer transformer = transformerFactory.newTransformer();
          transformer.setOutputProperty(OutputKeys.INDENT, "yes");
          StringWriter sw = new StringWriter();
          StreamResult result = new StreamResult(sw);
          DOMSource domSource = new DOMSource(document);
          transformer.transform(domSource, result);
          String xmlString = sw.toString();
          FileWriter fw=new FileWriter(file,true);
          BufferedWriter bw = new BufferedWriter(fw);
          bw.write(xmlString);
          bw.flush();
          bw.close();
          }
          catch(Exception e)
          {
         }
      }
     }
         public void buttonOnClick () throws ServletException, IOException {
             if (request.getParameter("btnUpdate") != null) {
              updateXML();
           }
        }
   %>
function getOutput()
{
  if (xmlhttp.readyState==4)
  {
  document.getElementById("nameInput").innerHTML=xmlhttp.responseText;
  }
}
function loadXMLDoc(dname) {

              if (window.XMLHttpRequest) {
                  xmlhttp = new XMLHttpRequest();
              }
              else {
                  xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
              }
               xmlDoc.async = false;
                 xmlDoc.load(dname);
                xmlDoc.save("Employees.xml");
                return (xmlDoc);
         }
 function Names() {
      var xml = getXML();
      var txt = "";
      $(xml).find("Person").each(function () {
        txt += "<div>" + $(this).text() + "</div>";
      });
      $("body").append(txt);
    }
    Names();

我的XML文件：

<People>
  <Person>George</Person>
<Person>Mary</Person>
<Person>John</Person>
</People>

现在，每次我点击更新按钮，我都会把旧文件的内容一次又一次地"粘贴"到div上。它不发布用户输入。我哪里错了？如有任何帮助，我们将不胜感激。