AJAX调用

/*
 * Returns a new XMLHttpRequest object, or false if this browser
 * doesn't support it
 */
function newXMLHttpRequest() {

  var xmlreq = false;

  if (window.XMLHttpRequest) {

    // Create XMLHttpRequest object in non-Microsoft browsers
    xmlreq = new XMLHttpRequest();

  } else if (window.ActiveXObject) {

    // Create XMLHttpRequest via MS ActiveX
    try {
      // Try to create XMLHttpRequest in later versions
      // of Internet Explorer

      xmlreq = new ActiveXObject("Msxml2.XMLHTTP");

    } catch (e1) {

      // Failed to create required ActiveXObject

      try {
        // Try version supported by older versions
        // of Internet Explorer

        xmlreq = new ActiveXObject("Microsoft.XMLHTTP");

      } catch (e2) {

        // Unable to create an XMLHttpRequest with ActiveX
      }
    }
  }
	
  return xmlreq;
}
  
/**
 *url			提交的路径
 *parameters	参数对（例如：param1=v1&param2=v2）
 *callback		回调函数
 *
 *如果要传输的数据过长需要将数据组织成参数对的形式传到parameters
 *服务器端程序在取数据时候需要增加UTF-8编码，例如
 *String curValue = java.net.URLDecoder.decode(request.getParameter(param), "UTF-8");
 */
function execService(url, parameters,callback) {
	var xmlhttp = newXMLHttpRequest();
	
	if(xmlhttp == null){
		alert("初始化失败");
		return ;
	}
	var async = false;
	if (arguments.length == 3){ 
		async=true;
	}
	xmlhttp.open("POST", url, async);
	//修改url超长的问题 
	xmlhttp.setRequestHeader("Cache-Control","no-cache");
	xmlhttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
	if (async) { 
		var f = function() {
			if (xmlhttp.readyState==4) {
				callback(xmlhttp.responseText);
			}
		}
		xmlhttp.onreadystatechange = f;
	}
	parameters=encodeURI(parameters);
	parameters=encodeURI(parameters);
	xmlhttp.send(parameters);
	
	if (!async) {
	    var obj = xmlhttp.responseText;
		if(typeof(obj) =='string' || typeof(obj) =='function' || typeof(obj) =='object')
		{
		  return xmlhttp.responseText;
		}
	}
}

getResponse().setContentType("text/html;charset=GBK");
StringBuffer buffer = new StringBuffer();
buffer.append("XXX");
buffer.append("YYY");
getResponse().getWriter().println(buffer.toString());
return null;