Ajax上传实现根据服务器端返回数据进行js处理的

package com.justsy.servlet; 
import java.io.IOException; 
import java.io.PrintWriter; 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
public class UploadServlet extends HttpServlet { 
  private static final long serialVersionUID = 1L; 
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
    this.doPost(request, response) ; 
  } 
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
    PrintWriter writer = response.getWriter() ; 
    response.setContentType("text/html") ; 
    writer.print("<root>ok</root>") ; 
  } 
} 

function submitForm(){ 
  $("#hidden_iframe").load(function(){ 
    var content = document.getElementById("hidden_iframe").contentWindow.document.body.innerHTML; 
    content = createXml(content); 
    var root = $(content).find("root").eq(0); 
    alert(root.text()); 
    $("#hidden_iframe").unbind("load"); 
  }); 
  document.getElementById("form2").submit(); 
} 
function createXml(str){ 
  if (document.all) { 
    var xmlDom = new ActiveXObject("Microsoft.XMLDOM"); 
    xmlDom.loadXML(str); 
    return xmlDom; 
  } 
  else { 
    return new DOMParser().parseFromString(str, "text/xml"); 
  } 
} 

<form action="uploadServlet.do" id="form2" enctype="multipart/form-data" method="post" target="hidden_iframe">
  <input type="hidden" name="method" value="uploadExcel" /><input type="button" value="Submit" onclick="submitForm()"/>
</form>
<iframe name="hidden_iframe" id="hidden_iframe" width="300" height="200">
</iframe>