From: "Mark Haney" <ma...@abemblem.com>
Subject: Re: Template toolkit issue [SOLVED]
On 05/02/2012 03:53 PM, Octavian Rasnita wrote:
Perl is a programming language, not a language which is used only for
web programming, so why should you think that Template Toolkit includes
CGI? Nowadays CGI is very seldom used, so others might be thinking that
it should include PSGI or another interface for web apps...
Of course, Template Toolkit is mostly used for creating HTML content,
but it can be used for generating any other type of content, so it
doesn't have any relation with HTML either.
Octavian
I'm really quite intrigued by the assertion that CGI is very seldom used.
Based on this entire thread, the Template Toolkit is used entirely for
building websites in perl. And unless I'm mistaken, what other way than
CGI could perl possibly be used in this manner? Granted, I'm no expert on
perl and web programming, I think I've made that clear.
OK, sorry for not beeing clear enough. I'll try again.
As you already read and probably knew, CGI has a double meaning.
First, it is an interface which is used by all programming languages for the
web in order to allow the browsers to submit forms to the web servers.
And second, it is a Perl module that does a few things:
- parses the query strings from URLS (those ?var1=val1&var2=val2)
- parses the content of POST requests (for getting the POSTed data, or
upload files...)
- generate HTTP headers
- create HTML elements by using many functions that have the same name as
the HTML elements.
The module CGI is a great module which does many helpful things, but it is
very seldom used these days, and even when it is used, not everybody likes
all its features.
The most important feature of this module is the fact that it can parse the
query strings from URLS and the POSTed content, but many programmers don't
like to use its methods to generate HTTP headers, and prefer to just print
them directly, like:
print "Content-Type: text/html\n\n";
Even more programmers don't like to use its features that allow generating
HTML elements with CGI.pm's methods, but prefer to use a templating system
like Template-Toolkit to do that, or even just print the HTML content as a
block of text (which is ugly).
But fewer and fewer sites use CGI.pm, because when using the standard Common
Gateway Interface, after the web server receives the request, it creates a
new process, and run Perl which compiles the CGI script and executes it, and
then return the result, after which the process is closed. And these steps
are done again and again on each request, so it works very slow.
There are better alternatives.
Instead of loading the script and compile it on each request, the script can
be loaded once, compiled, and the compiled version kept available in the
memory, and on subsequent requests the compiled program should just receive
the requests and return the responses which works much faster.
In order to do that, you need to use either mod_perl or FastCGI.
mod_perl is an Apache module, and Apache is a huge web server that consumes
a lot of resources, but this Perl module can work only under Apache, so it
is not very flexible. If Apache is OK for you, mod_perl is great but it is
more complicated to set it up and to work with it than by using CGI.pm.
FastCGI is an interface similar with mod_perl but which works with more web
servers including Apache, so it is more flexible, but it might be a little
more complicated to set up than mod_perl, but this depends on each one's
experience.
If your site is targetted to a very small number of users and if you don't
require a very high speed, then CGI.pm is a good solution if the page is not
very complicated.
If the page contains very many elements, and if you need to use different
modules like a templating system, then the speed of page rendering will
decrease even more, because it is obviously that a page that just prints an
HTML content directly is displayed faster than one that needs to load a
template, and let that template generate the content.
This is why most of the times when a page is complex enough and uses a
templating system, and accesses a database, and maybe use a form processor
like HTML::FormFu and maybe other modules, it also uses a persistent
environment that keeps the code compiled in memory and also maintain a
permanent connection to the database, so it shouldn't spend time connecting
to the database on each request.
Usually those who need to create a complex site also need to use a few tools
for creating that site, and don't reinvent the wheel and do it from the
scratch.
And those tools are usually a web framework, a templating system, an ORM, a
form processor and different other modules depending on their needs.
And all these tools are high-level code which make the site work slower than
when using just low-level Perl code, but the productivity increases very
much, and the speed of the site can be improved in other ways, (like using a
web proxy in front of more servers that run that site, or using cache at
different levels...).
The most used and most powerful Perl web framework is Catalyst, but there
are more other frameworks you can find on CPAN if you'll need.
The most used ORM is DBIx::Class but you can also find other ORMS if you
need.
The most elegant and used templating system is Template-Toolkit but again,
there are many other templating systems you can use, depending on your needs
and requirements.
And you can find a lot more information in the documentation of each module
on CPAN.
And there is a pretty new interface named PSGI which was ported from
Python's WSGI, and I could tell you some things about it, because you said
that you want to know what should be done and not only what shouldn't, but
probably it won't be very helpful for your current project so you can search
for it on CPAN if you really want to find more information.
But, it appears that I'm getting contradictory messages here, none of
which make me feel particularly comfortable with continuing to use perl
for my project.
I don't see which were the contradictory messages.
I'm also not used to being talked down to like a child. Why would I think
the Template Toolkit includes CGI? Well, if my OP had been read, you
would have seen that /in the example/ in the documentation, no mention of
including CGI in the code was made.
You said:
"I got it working now. I was under the assumption that the TEMPLATE
module included CGI and that adding CGI and going through the process of
generating the headers and specifying the beginning and ending of the
html was a given."
And I just told you that no, nothing is a given in Perl, unless you request
it.
Do you want to use CGI? Then use the CGI.pm module. Do you want to use a
templating system to generate the content of the web page? Then use the
templating system you choose. Do you want to be better informed about a
certain module like Templating-Toolkit or Catalyst, or DBIx::Class, or
HTML::FormFu, or Moose, then subscribe on the mailing list of that module,
because the popular Perl modules have their own mailing list.
Or you can ask on this list, no problem, but remember that Perl is not a
language that can be used only for web programming, and that the web related
things are not a given in Perl like in PHP, but you need to use the Perl
modules you want to use.
But then, I also made it clear that the documentation is worse than
useless. This was less an assumption on my part than simple ignorance.
I'm not certain how much clearer I can be when I say I'm /new/ to the
perl/web game. Is it so hard 1) to understand and 2) to consider the
audience when crafting a reply that might be useful and not derogatory?
The problem is that you are asking how to do in Perl some things, in the way
you are used to do them in PHP, and fortunately this is not possible, so you
should be asking how to do some things, not how to use some Perl tools to do
the things like in PHP.
Personally, the more replies I get on this list the less I'm inclined to
use perl for this, since I'm not getting as much help as I expected in a
/beginners/ list, but also I'm being given the impression that perl isn't
used the way I'm intending to use it.
Yes, I also have that impression. :-)
If you want to find a quick answer about how to do in Perl a program that
works like one in PHP, then you won't find that answer here.
You may find it elsewhere because in Perl there are possible very many
things, but the people on this list tend to give only good advices, and
using a PHP-style programming it might not be one of them.
In other words, I'm just about at the 'I give up' stage and moving
everything to a platform that has a good helpful community. My apologies
to those that have helped. It's been greatly appreciated, but I'm about as
frustrated as I can possibly be.
But why? I understood that you managed to make your program work because I
have seen "solved" in the subject of this thread....
If you are frustrated because I told you that CGI.pm is seldom used, then
don't bother because each one has its own preferences. Some people still use
CGI.pm because they don't require a very high speed. Some use a web
framework and an ORM because they need to do very many things very fast and
this increases the productivity, but others don't like them because they
require a steap learning curve. Some of them use mod_perl because they need
a very fast program and don't use a web framework that decreases the speed
because the speed is the most important for them and not the productivity.
Some use Plack/PSGI and one of the newer web servers that use this
interface, like Starman or Starlet, which are very fast, elegant and easy to
use or other web servers like nginx or lighttpd, some use Template-Toolkit
because it is very elegant and powerful and separates the Perl code and the
code used for formatting the output, but others like Mason. Some like
HTML::FormFu form processor and others like HTML::FormHandler and each one
have their preferences, so you will ever get "contradictory" messages
because in Perl there is no just a single good way, but many good ways,
depending on your needs.
In other programming languages a certain web framework usually works with a
single templating system and a single ORM, and another web framework works
with another templating system and another ORM, so you will be forced to
follow the single possible way, but in Perl, with Catalyst and Dancer and
Mojolicious and probably with other frameworks you can choose to use the
templating system you like, the ORM you like, the form processor you like if
you need one and so on.
But these are very advanced things compared with using CGI.pm for creating a
simple program and I told you about them to see how can be used Perl in the
right way.
Using CGI.pm for creating a kind of PHP parser is not a good way that should
be recommended to newbies.
IMHO I think you should keep using PHP.
There is no the best programming language, and depending on each one's
knowledge and needs, other languages like Python or Ruby or even PHP could
be better.
Octavian
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