<?xml version="1.0" encoding="UTF-8"?>
<!doctype html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<script language="JavaScript" src="lib/nirvanaAsyncObjJSNotation.js"></script>
<script>
var applicationName = "myTestApplication";
var channelName = "/tutorial/testchannel/";
var realm = "http://" + location.hostname + "/sv/nvLite";
var sessionName = "myExampleSession";
var username = "emcdaid2"; // note that in a real app,
// this should be an authenticated username!
var initialiasedASession = false;
var mySession = null;
var testChannel = null;
function isLoaded() {
/********************************************************************
* As soon as the page loads, we should create our Nirvana session.
* This method is invoked by the <body> tag's "onload" event.
* We initialise our session by passing in the names of two custom
* methods (which, like all such callback methods in this demo, we are
* free to name as we wish; we simply have to implement the methods).
* The first one ("sessionInitCB") is invoked if and only if the
* session creation was successful.
* The second one ("sessionRejectCB") is invoked if and only if the
* session creation failed for some reason.
*********************************************************************/
mySession = new nSession(realm, sessionName, username, "connectionCB", applicationName);
mySession.init("sessionInitCB", "sessionRejectCB");
}
function connectionCBDisconnected(){
/********************************************************************
* This method automatically gets invoked if/when we get disconnected.
* Note that th is is because we specified "connectionCB" as the prefix
* of the implicit "Disconnected" and "Reconnected" methods when we
* created the session (see fourth parameter in nSession constructor).
* A typical use for this method might be to disable UI components
* related to publishing (or to otherwise inform the user).
*********************************************************************/
alert("Disconnected");
}
function connectionCBReconnected(){
/********************************************************************
* This method automatically gets invoked if/when we get reconnected.
* Note that this is because we specified "connectionCB" as the prefix
* of the implicit "Disconnected" and "Reconnected" methods when we
* created the session (see fourth parameter in nSession constructor).
* A typical use for this method would be to re-enable UI components
* which might have been disabled during the disconnected period.
*********************************************************************/
alert("Reconnected");
}
function sessionInitCB(){
/********************************************************************
* This method automatically gets invoked when our mySession object
* is initialised. Note that this is because we specified
* "sessionInitCB" as the name of the "callback" method which should
* be executed after mySession.init completes.
*********************************************************************/
initialiasedASession = true;
window.status = "Session Initialised";
setupTestChannel();
}
function setupTestChannel() {
/********************************************************************
* Here we create an nChannelAttributes object, setting its name to
* that of the channel we wish to use. We then use our session to
* a) find the channel, then b) asynchronously invoke a method of our
* choice ("testChannelFoundCB") with the resulting channel object.
*********************************************************************/
var channelAttribs = new nChannelAttributes();
channelAttribs.setName(channelName);
mySession.findChannel( channelAttribs, "testChannelFoundCB" );
}
function testChannelFoundCB(chan) {
/********************************************************************
* This method automatically gets invoked when mySession.findChannel
* completes (since we specified "testChannelFoundCB" as the callback
* in the above method. Note that the found channel object is
* automatically passed in as a parameter.
*********************************************************************/
testChannel = chan;
if( testChannel == false ) {
/****************************************************************
* Oops. The channel could not be accessed for some reason.
* Try again in 500ms, say:
*****************************************************************/
setTimeout("setupTestChannel()", 500);
} else {
/****************************************************************
* The channel is valid, so let us subscribe and receive events
* from it. We shall specify that:
*
* a) the method "testChannelSubscriptionCompleteCB" should be
* invoked automatically when the subscription initialises,
*
* b) all consequent events received from the channel will
* automatically be passed as arguments to the method
* "myTestChannelEventHandlerCB".
*
* Of course, we now have to implement both of these methods too.
*****************************************************************/
var startEID = 0;
var evtHandler = "myTestChannelEventHandlerCB";
var subsCB = "testChannelSubscriptionCompleteCB";
testChannel.addSubscriberFromEID(evtHandler, startEID, subsCB);
}
}
function sessionRejectCB(){
/********************************************************************
* This method automatically gets invoked iff mySession.init fails
* (since we specified "sessionRejectCB" as the callback method to be
* invoked after failure (due, for example, to excessive connections).
*********************************************************************/
alert("Session Rejected");
}
function myTestChannelEventHandlerCB(event) {
/********************************************************************
* This method automatically gets invoked every time we receive an
* event from the testChannel (since this is the method we specified
* when we subscribed - see testChannelFoundCB method). Note that the
* event object will be passed to this method as a parameter. We can
* then get the event's data "dictionary", and read the value of any
* of its keys. In this demo, we use this data to update a textarea.
*********************************************************************/
var dictionary = event.getDictionary();
var newData = dictionary.get('publisher') + ": " + dictionary.get('message') + "\n"
var oldData = document.getElementById("outputTextarea").value;
document.getElementById("outputTextarea").value = newData + oldData;
}
function testChannelSubscriptionCompleteCB(){
/********************************************************************
* This method automatically gets invoked when we successfully
* subscribe to testChannel (since this is the method we specified
* when we subscribed - see testChannelFoundCB method).
*********************************************************************/
window.status = "Successfully subscribed to testChannel";
}
function publishMessage() {
/********************************************************************
* This method is an example of how to publish events to our channel.
* We first create an nConsumeEvent, and assign it an nEventProperties
* object (which represents a data"dictionary" - essentially a hash of
* key-value pairs). Finally, we call the channel's publish method,
* passing in the event along with (optionally) the name of a callback
* method to be invoked upon completion of the publishing attempt.
* It is good practice to wrap code like this in try/catch blocks.
*********************************************************************/
if (document.getElementById("demoInput").value == "") return;
try {
var evt = new nConsumeEvent();
var dictionary = new nEventProperties();
dictionary.put("publisher", username);
dictionary.put("message", document.getElementById("demoInput").value);
evt.setDictionary(dictionary);
testChannel.publish(evt, "postPublishCB");
} catch (error) {
alert("Error: " + error.message);
}
}
function postPublishCB() {
/********************************************************************
* This method automatically gets invoked after we successfully
* publish to testChannel (since this is the method we specified
* when we called testChannel.publish in our publishMessage() method).
* A typical use for this method would be to re-enable UI components
* that might have been disabled while publishing took place.
*********************************************************************/
if(!initialiasedASession) alert("We did not get a session to Nirvana");
document.getElementById("demoInput").value = "";
window.status = "Published";
}
</script>
<title>Nirvana webExpress: Pub/Sub with JavaScript</title>
</head>
<body onload="isLoaded()">
<h1>Nirvana webExpress: Pub/Sub with JavaScript</h1>
<form onsubmit="publishMessage(); return false;">
<h2>Input</h2>
<input type="text" id="demoInput"/>
<input type="submit" value="Publish">
<h2>Output</h2>
<textarea id="outputTextarea" rows="10" cols="70"></textarea>
</form>
</body>
</html>
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