How to send web browser a loading page, then some time later a results page
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by Kurt W. Leucht
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Published on 2010-04-05T21:44:15Z
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2010/04/06
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I've wasted at least a half day of my company's time searching the Internet for an answer and I'm getting wrapped around the axle here. I can't figure out the difference between all the different technology choices (long polling, ajax streaming, comet, XMPP, etc.) and I can't get a simple hello world example working on my PC.
I am running Apache 2.2 and ActivePerl 5.10.0. JavaScript is completely acceptable for this solution. All I want to do is write a simple Perl CGI script that when accessed, it immediately returns some HTML that tells the user to wait or maybe sends an animated GIF. Then without any user intervention (no mouse clicks or anything) I want the CGI script to at some time later replace the wait message or the animated GIF with the actual results from their query.
I know this is simple stuff and websites do it all the time using JavaScript, but I can't find a single working example that I can cut and paste onto my machine that will work in Perl.
Here is my simple Hello World example that I've compiled from various Internet sources, but it doesn't seem to work. When I refresh this Perl CGI script in my web browser it prints nothing for 5 seconds, then it prints the PLEASE BE PATIENT web page, but not the results web page. So the Ajax XMLHttpRequest stuff obviously isn't working right. What am I doing wrong?
#!C:\Perl\bin\perl.exe
use CGI;
use CGI::Carp qw/fatalsToBrowser warningsToBrowser/;
sub Create_HTML {
my $html = <<EOHTML;
<html>
<head>
<meta http-equiv="pragma" content="no-cache" />
<meta http-equiv="expires" content="-1" />
<script type="text/javascript" >
var xmlhttp=false;
/*@cc_on @*/
/*@if (@_jscript_version >= 5)
// JScript gives us Conditional compilation, we can cope with old IE versions.
// and security blocked creation of the objects.
try {
xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
} catch (E) {
xmlhttp = false;
}
}
@end @*/
if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
try {
xmlhttp = new XMLHttpRequest();
} catch (e) {
xmlhttp=false;
}
}
if (!xmlhttp && window.createRequest) {
try {
xmlhttp = window.createRequest();
} catch (e) {
xmlhttp=false;
}
}
</script>
<title>Ajax Streaming Connection Demo</title>
</head>
<body>
Some header text.
<p>
<div id="response">PLEASE BE PATIENT</div>
<p>
Some footer text.
</body>
</html>
EOHTML
return $html;
}
my $cgi = new CGI;
print $cgi->header;
print Create_HTML();
sleep(5);
print "<script type=\"text/javascript\">\n";
print "\$('response').innerHTML = 'Here are your results!';\n";
print "</script>\n";
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