Re: Using Javascript to find if Java applet has loaded

Hi Jason,

"Jason Carlton" <jwcarlton@gmail.com> wrote in message
news:a8e19be8-5116-4889-b26b-b1998b2d7c26@j19g2000yqk.googlegroups.com...


myAppletRef = document.getElementById(appletId);

Should handle most of your requirements and not return until the applet is
there. Having said that, if possiblem it should be followed up by some
method-call back into the Applet. And if you're usung LiveConnect then

sure the method you're calling is synchronized (and the init() is also
synchronized) as the init() has a nasty habbit of continuing on *after*

let the Javascript thread free :-(

Below is a more complete example.


Cheers Richard Maher

/**
 * Copyright (c) Richard Maher. All rights reserved.
 *
 * Tier3Client class bridges Javascript and Applet
 * functionality.
 */

function Tier3Client(application,
                     codeBase,
                     port,
                     maxBuf,
                     hostCharSet,
                     sslReqd,
                     guiToolkit,
                     idleTimeout,
                     verbosity)
{
    if (arguments.length < 4) {
        throw new Error("Insufficient arguments for Tier3Client");
    }

    if (!navigator.javaEnabled()) {
        alert("You must enable Java Applets in your browser\n" +
              "before you can successfully access this page");
        throw new Error("Java Applets are not enabled for browser");
    }

    this.application = application;
    this.codeBase = codeBase;
    this.port = port;
    this.maxBuf = maxBuf;

    this.hostCharSet = (hostCharSet == undefined) ? "ISO-8859-1" :
hostCharSet;
    this.sslReqd = (sslReqd == undefined) ? "N" :
sslReqd;
    this.guiToolkit = (guiToolkit == undefined) ? Tier3Client.GUIAWT :
guiToolkit;
    this.idleTimeout = (idleTimeout == undefined) ? 0 :
idleTimeout;
    this.verbosity = (verbosity == undefined) ? Tier3Client.WARNING :
verbosity;

    var appletId = "Tier3__" + application + "_Applet";

    try {
        var idTaken = document.getElementById(appletId);
    }
    catch (err) {};

    if (idTaken != null) {
        throw new Error("Tier3 Client already registered for " +
this.application);
        return;
    }

    var archiveName = "tier3Client.jar";
    var className = "tier3Client/Tier3Application";

    var appletParams = [{"name":"archive",
    "value":archiveName },
                        {"name":"codebase",
"value":codeBase },
                        {"name":"code",
     "value":className },
                        {"name":"java_version",
":"1.6+" },
                        {"name":"mayscript",
lue":"true" },
                        {"name":"scriptable",
ue":"true" },
                        {"name":"codebase_lookup",
"false" },
                        {"name":"APPLICATION",
"value":application },
                        {"name":"PORT",
"value":port },
                        {"name":"MAXBUF",
"value":maxBuf },
                        {"name":"HOSTCHARSET",
"value":this.hostCharSet},
                        {"name":"SSLREQD",
     "value":this.sslReqd },
                        {"name":"GUITOOLKIT",
     "value":this.guiToolkit },
                        {"name":"IDLETIMEOUT",
"value":this.idleTimeout},
                        {"name":"VERBOSITY",
     "value":this.verbosity }];
    var startParam = 0;

    var objectTag = "<object classid=";

    if (/Internet Explorer/.test(navigator.appName)) {
        objectTag = objectTag +
            '"clsid:8AD9C840-044E-11D1-B3E9-00805F499D93" ';
    } else {
        objectTag = objectTag +
            '"java:' + className + '.class"

' +
            'archive="' + codeBase + archiveName + '" ';
        startParam = 1;
    }

    objectTag = objectTag + ' width= "0" height= "0" id="' + appletId +
'">';

    for (i=startParam; i<appletParams.length; i++){
        objectTag = objectTag + '<param name ="' + appletParams[i].name

'" ' +
                                       'value ="' + appletParams[i].value

'">';
    }

    objectTag = objectTag + "</object>";

    var appletDiv = document.createElement("div");
    appletDiv.innerHTML = objectTag;

    try {
        document.body.appendChild(appletDiv);
        this.chan = document.getElementById(appletId);
    }
    catch(err) {
        alert("Tier3 unable to load applet for " + this.application +
": -\n" + err.description);
        this.chan = null;
    };

    if (this.chan == null) {
        throw new Error("Tier3 was unable to initialize the applet for " +
this.application);
    } else {
        try {
            if (!this.chan.isAuthorized()) {
                throw new Error("Tier3 User Authentication unsuccessful

" + this.application);
            }
        }
        catch(err) {
            this.chan.setAttribute("id",null);
            this.chan = null;
            throw new Error("Tier3 unable to load applet for " +
this.application + ": -\n" + err.description);
        }
    }

    Tier3Client.applications[this.application] = this;

    return this;
}

Tier3Client.FACPREFIX = "T3$";
Tier3Client.MAJVERS = 1;
Tier3Client.MINVERS = 0;
Tier3Client.GUIAWT = 1;
Tier3Client.DEBUG = 0;
Tier3Client.INFO = 1;
Tier3Client.WARNING = 2;
Tier3Client.ERROR = 3;
Tier3Client.FATAL = 4;

Tier3Client.errorPage = "Tier3Error.html";
Tier3Client.logoffPage = "Tier3Logoff.html";

Tier3Client.launder =
    function(jsobject) {
        return jsobject;
    };

Tier3Client.prototype = {

    send:
        function(msgBody, callback, async)
        {
            if (arguments.length < 2) {
                throw new Error("Insufficient arguments for send(msgBody,
callback)");
            }

            if (typeof callback != "function") {
                throw new Error("The 'callback' parameter must be a
function");
            }

            var noWait = true;
            if (arguments.length > 2) {
                if (typeof async != "boolean") {
                    throw new Error("The 'async' parameter must be a
boolean");
                }
                noWait = async;
            }

            var chan = this.chan;
            var callbackArgs = new Array();
            var responseCnt = 0;
            var i = 0;

            var msgCandidate =
            {
                msgSlotId : -1,
                msgSeqNum : -1,
                chan : chan,
                callback : callback,
                callbackArgs : callbackArgs,

                dispatcher :
                    function(responseMsg,
                             msgSlotId,
                             msgSeqNum)
                    {
                       this.responseCnt++;
                       this.msgSlotId = msgSlotId;
                       this.msgSeqNum = msgSeqNum;
                       callbackArgs[0] = responseMsg;

                       try {
                           callback.apply(this, callbackArgs);
                       }
                       catch (err) {
                           throw new Error("Error calling callback
routine: -\n" + err.description);
                       }
                    },

                getMsgSeqNum :
                    function() {
                        return this.msgSeqNum;
                    },

                getResponseCnt:
                    function() {
                        return this.responseCnt;
                    },

                rendezvous :
                    function() {
                        return chan.rendezvous();
                    }

            };

            for (i=3; i<arguments.length; i++) {
                callbackArgs[i - 2] = arguments[i];
            }

            return chan.send(msgCandidate, msgBody, noWait);
        },

    appendConsoleMsg:
        function(msg)
        {
            this.chan.appendConsoleMsg(msg);
        }
};

Tier3Client.applications = {};