openrgjnet jrms中服务器推送议程什么ajaxajax阿贾克斯.pptxVIP

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AJAX(AsynchronousJavaScriptAndXML)ServerPush

in

OpenRGandJNET/JRMS

2AgendaWhatisAJAXAJAXJavaScript(XMLHTTPObject)AJAXinOpenRGandJNET/JRMS

3HistoryandConceptSendandReceivedatato/fromserver.CanbeusedtoupdatepagedisplaywithoutrefreshingentirepageTechnologyexistssince1996butwasfirstintensivelyusedbyGooglein2004(GMail,Googlemaps)ServerPush–pagerefreshistriggeredbyserverwhenrefreshisneeded(notpollingbythebrowser)

4AJAX–XMLHTTPObjectfunctiongetXMLHTTPObject(){ varxmlHttp; try{//Firefox,Opera8.0+,Safari

xmlHttp=newXMLHttpRequest();

}catch(e){//InternetExplorer

try{

xmlHttp=newActiveXObject(Msxml2.XMLHTTP);

}catch(e){

try{

xmlHttp=newActiveXObject(Microsoft.XMLHTTP);

}catch(e){

alert(YourbrowserdoesnotsupportAJAX!);

returnfalse;

}

…

5AJAX–XMLHTTPObject(cont.)functionsendAJAXRequest(url,handler){ varobj=getXMLHTTPObject(); obj.onreadystatechange=function() { if(obj.readyState==4) handler(obj.responseText); } obj.open(“GET”,url,true); obj.send(null);}

6AJAX–XMLHTTPObject(cont.)functionhandleAJAXResponse(html){ document.getElementById(‘ajax_text’).innerHTML=html;}functionfoo(){ sendAJAXRequest(“ajax_text.html”,handleAJAXResponse);}

7AJAX–XMLHTTPObject(cont.)CanalsobeusedtoupdateserverwithoutpostingpageServerresponsecanbeanytext(notnecessarilyhtml)Handlercandocomplicatedprocessing(notjustreplaceinnerHTML)AJAXrequesthasatimeoutRealimplementationshoulddofurthercheckingonresponse(e.g.status)OthermethodsofXMLHTTPObjectexist(e.g.setRequestHeader)

8AJAX–Example(example.html)htmlhead scripttype=“text/javascript”src=“ajax.js”/script/headbodyonload=“setTimeout(‘foo()’,5000)” divid=“ajax_text” fontcolor=“0xFF0000”HelloAJAX/font /div/body/html

9AJAX–Example(ajax_text.html)bfontcolor=“0x0000FF”HelloAJAXinBOLD/font/b

10AJAXbasiclayer(server_push.[ch])/*inittheserverpushmechanism.