Ajax跨域实现代码(后台jsp)

function createXMLHttpRequest(){
 var xmlhttp;
 try{
  xmlhttp = new XMLHttpRequest();//ie7及以上，其他浏览器
 }catch(e){
  try{
   xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");//ie6
  }catch(e){
   try{
    xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");//ie6以下
   }catch(e){
    throw "创建AJAX对象失败！";
   }
  }
 }
 return xmlhttp;
 }


 var xmlhttp = createXMLHttpRequest();
  xmlhttp.open("GET","http://localhost:8080/SimpleBlog/AjaxTest",true);
  xmlhttp.send(null);
  xmlhttp.onreadystatechange = function(result){
  if(xmlhttp.readyState==4 && xmlhttp.status == 200){
   alter(result.test);
  }
 };

function get() {
  var url = 'http://localhost:8080/SimpleBlog/AjaxTest?callback=callback';
  var script = document.createElement('script'); 
  script.setAttribute("type","text/javascript"); 
  script.src = url; 
  document.body.appendChild(script); 
 }
 
 function callback(va){
  alert(va.test);
 }

 boolean jsonP = false;
 String cb = this.request.getParameter("callback");
 if (cb != null) {
 jsonP = true;
 response.setContentType("text/javascript");
 } else {
  response.setContentType("application/x-json");
 }
 PrintWriter out = response.getWriter();
 if (jsonP) {
  try {
   out.println(cb + "({\"test\":\"1\"})");
   out.flush();
   out.close();
  } catch (Exception e) {
   throw e;
  }
 }

$(document).ready(function (){
  $('#jqueryajax').bind('click', function(){
  $.ajax({
   type: 'get',
   async: false,
   url: 'http://localhost:8080/SimpleBlog/AjaxTest1',
   dataType: 'jsonp',
   jsonp: 'callback',
   success: function(json){
    alert(json.result);
   },
   error: function(){
    alert('fail');
   }
  });
  });
 });

public class AjaxTest1 extends ActionSupport {

 private String result;
 public String getResult() {
  return result;
 }
 
 public String execute() {
 
  this.result = "1";
  return "jqueryajax";
 }
}

<action name="AjaxTest1" class="AjaxTest1">
 <result name="jqueryajax" type="json">
  <param name="callbackParameter">callback</param>
 </result>
 </action>

function createCORSRequest(method,url){
  var xhr=new XMLHttpRequest();
  if('withCredentials' in xhr){
  xhr.open(method,url,true);
  }else if(typeof XDomainRequest!='undefined'){
   xhr=new XDomainRequest(); 
   xhr.open(method,url);
  }else{
   xhr=null;
  }
  return xhr;
 }
 
 function xhr2(){
  var request=createCORSRequest('GET','http://localhost:8080/SimpleBlog/AjaxTest1');
  if(request){
  request.onload=function(){
   alert(request.responseText);
  }
  request.onerror=function(e){
   alert('error');
  }
  request.send();
  } 
 }