The operation realization of Ajax in struts2 and the use of its core object XMLHttpRequest object __ajax

In a Web page file, the following XMLHttpRequest object can be used to implement the asynchronous operation of Ajax

function Getvaluefromserver () {var xmlhttprequest = null; if (window. 
				
			ActiveXObject) {//If the XMLHttpRequest is implemented through Microsoft ActiveXObject = new ActiveXObject ("Microsoft.XMLHTTP"); else if (window.
				XMLHttpRequest) {//If it is implemented through Firefox and Chrome.
			XMLHttpRequest = new XMLHttpRequest (); } if (null!= XMLHttpRequest) {//Method True is in asynchronous mode, and false is sending get requests synchronously, "Myservlet" represents the relative URL of the request Xmlhttpreque
				
				St.open ("Get", "addaction" + "? value1=" + value1 +  "&value2=" + value2,true);
				Xmlhttprequest.onreadystatechange = Ajaxcallback; /* If the request being sent is a get type, the parameter assignment null if a request parameter is added to "Myservlet" in Xmlhttprequest.open ("Get", "Myservlet", true), in the form of "Myservlet?"
			Username=hello&password=world "If the parameter of the type of post is unloaded in the form of a name-value pair, the Send () method is Xmlhttprequest.send (null).
					function Ajaxcallback () {if (xmlhttprequest.readystate = 4) {//http request is correct (200) if (Xmlhttprequest.status = = 200) {//The requested data format is plain text.
						
						var responsetext = Xmlhttprequest.responsetext;
					document.getElementById ("Div1"). InnerHTML = ResponseText; }
				}
			}
		}

As for the server side can take the following code to cooperate (if use is struts2 words)

Servletresponse HttpServletResponse = Servletactioncontext.getresponse ();
		
		PrintWriter printwriter = null;
		
		Try
		{
			 printwriter = Httpservletresponse.getwriter ();
		}
		catch (IOException e)
		{
			e.printstacktrace ();
		}

A signal can be generated from the object of the PrintWriter class and passed back to the client. There is a xmlhttprequest.responsetext in the callback function defined in the previous JavaScript script segment; The indicator is a normal text format rather than an XML format and is not a JSON data format. And the value inside is the data returned by the PrintWriter object.

function Ajaxcallback ()
{
if (xmlhttprequest.readystate = 4)
{
HTTP request is correct (200)
if (Xmlhttprequest.status = 200)
{
The requested data format is plain text.
var responsetext = Xmlhttprequest.responsetext;

document.getElementById ("Div1"). InnerHTML = ResponseText;
}
}
}

If it's a servlet, it's straight.

PrintWriter printwriter = Resp.getwriter (); Res is a HttpServletRequest object