AJAX底层操作方法

//Action中向按钮传递的value，try后面写需要执行的功能
try {
	response.setCharacterEncoding("UTF-8");
	PrintWriter pw = response.getWriter();
	pw.println(" 已点击 ");
	pw.flush();
	pw.close();
	} catch (Exception e) {
		e.printStackTrace();
}

//JSP中的JS代码
function btChange(bt){
     if(bt == 1){
     XMLHttpReq = createXMLHttpReq();
     XMLHttpReq.open("POST", "这里是需要执行的 Action方法", true);
     XMLHttpReq.onreadystatechange = processResponse;
     XMLHttpReq.send();
	}
}
function processResponse() {
 if (XMLHttpReq.readyState == 4) {
  var message = false;
  if (XMLHttpReq.status == 200) {
   message = XMLHttpReq.responseText;
//获取JSP中的按钮，并对其value值进行赋值，message为Action中传递过来的值
   var upButton = document.getElementById("upButton");
       upButton.value = message;
       alert(message);
//让按钮失效，即变为灰色
       document.getElementById("upButton").disabled="true";
  }
 }
}
	
function createXMLHttpReq() {
 XMLHttpReq = false;
 if (window.XMLHttpRequest) {
  XMLHttpReq = new XMLHttpRequest();
 } else {
  if (window.ActiveXObject) {
   try {
    XMLHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
   }
   catch (e) {
    try {
     XMLHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
    }
    catch (e) {
    }
   }
  }
 }
 return XMLHttpReq;
}