Ajax Asynchronous server Get time

1. Creating Ajax Objects

    <Scripttype= "Text/javascript">        //Creating an Ajax asynchronous Object        functionCreateajax () {varAjax= NULL; Try{                //if Ie5=ie12.Ajax= NewActiveXObject ("Microsoft.XMLHTTP"); }Catch(E1) {Try{                    //if it's non-ie,Ajax= NewXMLHttpRequest (); }Catch(E2) {alert ("Async objects are not supported in your browser, please change the browser"); }            }            returnAjax; }    </Script>

2. Add Get Time button

Current time:<id= "Time"></span><BR  /><ID= "ButtonID"  type= "button"  value= "Get current Time"/><p/>

3. Processing the data returned by Ajax in HTML

<Scripttype= "Text/javascript">document.getElementById ("ButtonID"). onclick= function(){            //NO1) Creating an Ajax asynchronous Object            varAjax=Createajax (); //NO2) ready to send the request            varMethod= "GET"; varURL= "${pagecontext.request.contextpath}/ajaxtimeservlet?time=" + NewDate (). GetTime ();            Ajax.open (Method,url); //NO3) actually sends the data of the request body to the server, if there is no data in the request body, it is represented by nullAjax.send (NULL); //-------------------------------------------------------------Wait                    //NO4) Ajax asynchronous object constantly listens for server response status 0-1-2-3-"4"            //You must change the state to trigger function () {}            //if the state is always 4-4-4-4-4, it will not trigger the function () {}Ajax.onreadystatechange= function(){                //If the status code is 4,                if(Ajax.readystate== 4){                    //If the response code is 200,                    if(Ajax.status==  $){                        //NO5) Gets the HTML data for the server response from the Ajax asynchronous object                        varNowstr=Ajax.responsetext; //NO6) Dynamically add results to the label specified in the Web page according to DOM rules                        varspanelement=document.getElementById (" Time"); Spanelement.innerhtml=Nowstr; }                }            }                     }

4. Java's handling of Ajax

/*** No need to refresh the entire Web page to display the current time of the server response*/ Public classAjaxtimeservletextendsHttpServlet { Public voidDoget (HttpServletRequest request, httpservletresponse response)throwsservletexception, IOException {simpledateformat SDF=NewSimpleDateFormat ("Yyyy-mm-dd HH:mm:ss"); String Nowstr= Sdf.format (NewDate ()); //stream the results to an Ajax asynchronous objectResponse.setcontenttype ("Text/html;charset=utf-8"); PrintWriter PW=Response.getwriter ();        Pw.write (NOWSTR);        Pw.flush ();    Pw.close (); }}

Ajax Asynchronous server Get time