I'm sorry Michael but I no longer have a working example. It's not hard to
create though - here's a quick and dirty effort based on the case Harald
described below, you might have to tweak and debug a little to get it
working smoothly, because I have forgotten the exact JS syntax and I haven't
got time to test it. Hope this helps :)
1. Write a servlet called "DataUpdateCheck" that checks the database thread
for new data, and depending on whether there is new data or not, returns to
the browser EITHER this:
<html>
<head>
<script language="JavaScript">
<!--
delay=3500; // this could be substituted using a config value from
web.xml
updateUri = "/mywebApp/DataUpdateCheck"; // change this to suit your webapp
x=setTimeout('document.location = "' + updateUri + '";', delay);
//-->
</script>
</head>
</html>
OR this:
<html>
<head>
<script language="JavaScript">
<!--
updateUri = "/mywebApp/MainDataPage"; // change this to suit your webapp
document.parent.mainDataFrame.location=updateUri;
//-->
</script>
</head>
</html>
2. Write a servlet called "MainDataPage" which produces the data display for
the user. You will probably have written this page already.
3. Then write a HTML page that combines the two servlets above:
<HTML>
<HEAD>
<TITLE></TITLE>
</HEAD>
<frameset rows="0,*">
<frame name="dataUpdateCheckFrame" src = "DataUpdateCheck">
<frame name="mainDataFrame" src = "MainDataPage">
</frameset>
</HTML>
You could probably use <IFRAME>s instead of <FRAME>s to make things look
neater in the browser.
> -----Original Message-----
> From: Michael McGrady [mailto:[EMAIL PROTECTED]
> Sent: Tuesday 19 October 2004 14:57
> To: Tomcat Users List
> Subject: [OT] Re: Push-Server with Tomcat
>
>
> Do you have a simple sample of this Steve? If so, I would
> sure like to
> see it.
>
> Michael McGrady
>
> Steve Kirk wrote:
>
> >Not sure if this is stating the obvious, or this is the
> approach you've
> >already taken, but it's not necesary to refresh the whole
> page that is
> >displaying your data every few seconds. You can have an
> invisible frame
> >that runs the JS timer that you describe. That frame could have
> >src="/mywebapp/DataUpdateCheck" which is a servlet that
> returns just a
> >simple js function - if there is new data, the function
> reloads it into the
> >visible frame, otherwise it reloads itself after a couple of
> seconds to
> >check for more data.
> >
> >
> >
> >>-----Original Message-----
> >>From: Steve Kirk [mailto:[EMAIL PROTECTED]
> >>Sent: Tuesday 19 October 2004 12:41
> >>To: 'Tomcat Users List'; [EMAIL PROTECTED]
> >>Subject: RE: Push-Server with Tomcat
> >>
> >>
> >>
> >>Seems to me that browsers are inherently "pull" technology
> >>because at the
> >>basic level they send a single request and await a single
> >>response to it.
> >>You can't push stuff at them that they haven't requested.
> >>Hence why you
> >>have to use an approach like your javascript - which, by the
> >>way, I have
> >>used in the past in a web-based control system without
> >>problems - it might
> >>not feel that elegant, but it does work.
> >>
> >>I would think that to get a true push approach you would have
> >>to extend the
> >>browser capabilities using a plugin of some sort, e.g. java
> >>applet / activex
> >>/ etc. Never tried this myself though so can't comment if
> >>this will solve
> >>it.
> >>
> >>
> >>
> >>>-----Original Message-----
> >>>From: Harald Henkel [mailto:[EMAIL PROTECTED]
> >>>Sent: Tuesday 19 October 2004 09:51
> >>>To: Tomcat Users List
> >>>Subject: Push-Server with Tomcat
> >>>
> >>>
> >>>Hello everybody.
> >>>
> >>>Is it possible (with Tomcat) to write an application that,
> >>>once startet
> >>>will send a new HTML page to a client, genereated using
> changed data
> >>>from a database ?
> >>>
> >>>What I want to do is using oracle alerts to alert a waiting Tomcat
> >>>thread of changed data, let it collect the data and generate
> >>>one or more
> >>>HTML pages sent to different clients, i.e. a specific frame in the
> >>>browser on the client.
> >>>
> >>>Or would I have to have a Java app runing in that frame ?
> >>>
> >>>At the moment I'm doing this using a JavaScript timer on the client
> >>>requesting a new page for that frame every couple of seconds,
> >>>but for this application push would really be better.
> >>>
> >>>With kind regards,
> >>>Harald Henkel
> >>>
> >>>--
> >>>Harald Henkel
> >>>
> >>>GS automation GmbH
> >>>Winterstraße 2
> >>>82223 Eichenau
> >>>Germany
> >>>Tel: + 49-8141-35 731-37
> >>>Fax: + 49-8141-35 731-38
> >>>Mobile: + 49-178-7829126
> >>>e-mail: [EMAIL PROTECTED]
> >>>Web: www.GS-automation.DE
> >>>
> >>>
> >>>
> >>>
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