<?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/Nirvana.js"></script>
<script>
var appName = "myTestApplication";
var channelName = "/tutorial/testchannel/";
var realm = "nhp://" + location.hostname + ":80";
var sessionName = "myExampleSession";
var username = "emcdaid"; // note that in a real app,
// this should be an authenticated username!
var connected = false;
var isLoadedCounter = 0;
var mySession = null;
var testChannel = null;
var isTimedOutConnectingCounter = 0;
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 a realm address, a sessionid,
* a username and a "prefix" for connection listener callback methods.
* The last parameter is the connection listener "prefix". As we chose
* to use the string "conHandlerCB" as the prefix, we must now implement
* four methods to receive asunchronous notifications of our connection
* status: conHandlerCBgotInitialConnection, conHandlerCBdisconnected,
* conHandlerCBreconnected and conHandlerCBtryAgain.
* Note that we could use any string as a prefix; we simply need to
* name our four implemented methods accordingly.
*********************************************************************/
// the nJSCRIPT variable is set by the applet when it initially loads
if ( typeof nJSCRIPT == "undefined" ) {
if ( isLoadedCounter > 4) {
window.status = "unable to initialise Nirvana libraries";
return;
}
else{
setTimeout("isLoaded()", 4000);
}
}
else if ( nJSCRIPT == true ) {
window.statys = "nApplet has been initialised.";
// session is initialised with a realm address, a sessionid,
// a username and a connection listener callback stub.
mySession = new nSessionWithSubjectAndReconnectionHandler(realm, appName, username, "conHandlerCB");
mySession.init();
connectionTimeoutMonitor();
}
}
function connectionTimeoutMonitor() {
/********************************************************************
* This method is used to allow the web page to give up on attempting
* to get an initial connection after a certain number of retries are
* unsuccessful.
*********************************************************************/
isTimedOutConnectingCounter++;
if ( mySession.isConnected() ) {
return;
}
else if (isTimedOutConnectingCounter < 4) {
setTimeout("connectionTimeoutMonitor()", 4000);
}
else if (isTimedOutConnectingCounter == 4) {
timedOutConnecting = true;
window.status = "Timed out connecting to Nirvana. ";
document.getElementById('Nirvana').stop();
return;
}
}
function conHandlerCBdisconnected() {
/********************************************************************
* This method automatically gets invoked we get disconnected from our
* Nirvana session. Note that this is because we specified
* "conHandlerCB" as the prefix of the implicit "disconnected",
* "reconnected","initialConnection" & "tryAgain" methods when we
* created the session (see fourth parameter in the constructor for
* nSessionWithSubjectAndReconnectionHandler).
* A typical use for these method would be to re-enable UI components
* which might have been disabled during the disconnected period.
* See also the tryAgain method, which allows us to specify whether
* the application should attempt to reconnect automatically after a
* disconnect has occured.
*********************************************************************/
connected = false;
alert("Disconnected");
}
function conHandlerCBreconnected() {
/********************************************************************
* This method automatically gets invoked we get reconnected to our
* Nirvana session after a disconnect too place. Note that this is
* because we specified "conHandlerCB" as the prefix of the implicit
* "disconnected","reconnected","initialConnection" & "tryAgain"
* methods when we created the session (see fourth parameter in the
* nSessionWithSubjectAndReconnectionHandler constructor).
* A typical use for these method would be to re-enable UI components
* which might have been disabled during the disconnected period.
* See also the tryAgain method, which allows us to specify whether
* the application should attempt to reconnect automatically after a
* disconnect has occured.
*********************************************************************/
connected = true;
alert("Reconnected");
}
function conHandlerCBgotInitialConnection() {
/********************************************************************
* This method automatically gets invoked we get the inital connection.
* Note that this is because we specified "conHandlerCB" as the prefix
* of the implicit "disconnected","reconnected","initialConnection" &
* "tryAgain" methods when we created the session (see fourth parameter
* in the nSessionWithSubjectAndReconnectionHandler constructor).
* A typical use for these method would be to wait for confirmation
* that the session has initialised before continuing with any other
* processing.
*********************************************************************/
connected = true;
window.status = "Connected to Nirvana.";
setTimeout("handleNewConnection();", 500);
}
function conHandlerCBtryAgain() {
/********************************************************************
* This method automatically gets invoked after each attempt to
* reconnect to a disconnected Nirvana session. This allows the
* developer to control whether or not continued attempts should be
* made to reconnect. Note that this is because we specified
* "conHandlerCB" as the prefix of the implicit "disconnected",
* "reconnected","initialConnection" & "tryAgain" methods when we
* created the session in our isLoaded() method.
* This method allows us to specify whether the application should
* attempt to reconnect automatically after a disconnect has occured.
*********************************************************************/
return true;
}
function handleNewConnection() {
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) subscribe to the channel.
*********************************************************************/
if (connected) {
var channelAttribs = new nChannelAttributes();
channelAttribs.setName(channelName);
testChannel = mySession.findChannel( channelAttribs, "testChannelFoundCB" );
// make sure we have a usable channel object
if (testChannel == false) {
if (mySession.isConnected()) {
// Channel could not be found. Let us try again.
// Maybe channel does not exist, or channel ACL is incorrect
setTimeout("setupTestChannel()", 2000);
} else {
// waiting for disconnect
setTimeout("setupTestChannel()", 4000);
}
} else {
// Add subscriber to the channel object
var startEID = 0;
var evtHandler = "myTestChannelEventHandlerCB";
testChannel.addSubscriberFromEID(evtHandler, startEID)
}
} else {
// if we were disconnected when this method was called, try again
setTimeout("getServerTime()", 4000);
}
window.status = "";
}
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 data (which is a byte[]), and/or its "dictionary"
* which contains a set of key-value pairs. In this demo, we use the
* dictionary keys "publisher" and "message", and 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 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 publish our event to the channel.
*********************************************************************/
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);
} catch (error) {
alert("Error: " + error.message);
}
}
</script>
<title>Nirvana webExpress: Pub/Sub with JavaScript</title>
</head>
<body onload="isLoaded()">
<h1>Nirvana : Pub/Sub with Java to JavaScript Bridge</h1>
<applet
codebase = "/jars/"
archive = "nClient.jar,nSigned.jar,nApplet.jar"
code = "com.pcbsys.Nirvana.client.jscript.NirvanaAppletThreaded.class"
id = "Nirvana"
name = "Nirvana"
MAYSCRIPT
width = "0"
height = "0"
hspace = "0"
vspace = "0"
align = "bottom"
>
</applet>
<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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