servlet 中request为空

我写了一段AJAX代码，执行servlet程序
问题是servlet 中request为空

js代码：
function nameChange(name) {

var xhr = new XMLHttpRequest();
var url = "http://localhost:8080/TEST/index";
var sync = true;
var type = "post";
xhr.open(type, url, sync);
xhr.onreadystatechange = function() {

if (xhr.readyState == 4 && xhr.status == 200) {
var text = xhr.responseText;
// var json = eval("("+text+")");
var name = document.getElementById("name");
alert(text);
if (text == "true") {
name.innerHTML = "<font style='font-size: 20px'>yes</font>";
} else {
name.innerHTML = "<font style='font-size: 20px'>no</font>";
}
}
};
xhr.send("nametext=" + name.value);

}

jsp代码：
  <form action="#">
  <table>
  <tr><td>name:</td><td><input type="text" id="nametext" onblur="nameChange(this)"/></td><td id="name"></td></tr>
 
  <tr><td><input type="submit" value="sumbit"/></td><td><input type="reset" value="cancel"/></td><td></td></tr>
  </table><font style="font-size: 20px"></font>
  </form>

servlet代码：
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {



response.setContentType("text/html");
request.setCharacterEncoding("utf-8");
PrintWriter out = response.getWriter();

String nametext = (String)request.getParameter("nametext");
String pwdtext = request.getParameter("pwdtext");

Map map = request.getParameterMap();

System.out.println(map);

System.out.println("name:"+nametext);//结果为null
System.out.println("pwd:"+pwdtext);//结果为null

if("martin".equals(nametext)){
out.print("true");
}
if("martin".equals(pwdtext)){
out.print("true");
}
}

CSS code

var name = document.getElementById("name");不是nametext么
你alert(name.value);有没有值看看
xhr.send("nametext=" + name.value);