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I'm going to start my first perl project which is going to be a simple record tracking system.
I plan to use template toolkit for rendering views with data and individual perl modules to handle things like reporting and database queries, hopefully getting a basic OOP style application going.
My confusion is: how should I handle requests? Should I have a routes.pl file, where I can listen for all GET/POST requests and based on those requests, call the appropriate .pm method and return a TT template, basically acting like a front controller? (I come from the PHP framework world, if that helps to understand my viewpoint)
Simple things rarely stay simple, so you should not go the route of rolling your own dispatcher. You'll be reinventing wheels which others have already long solved. And, by going with a framework you're also getting a lot of extra functionality for free, usually through plug-ins.
Have a look at the various Perl frameworks, the ones I can readily think of:
Dancer (http://www.perldancer.org/)
Mojolicious (http://mojolicio.us/)
Mason + Poet (http://www.masonhq.com/)
Catalyst (http://www.catalystframework.org/)
I only have experience with Mason + Poet and Catalyst, though Catalyst is far from simple.
I have been trying to decide if my web project is a candidate for implementation using PSGI, but I don't really see what good it would do for my application at this stage.
I don't really understand all the fuss. To me PSGI seems like a framework that provides a common interface between different Apache modules which lets you move your application between them. e.g Easily move your application from running on mod_perl to fastcgi, and provide the application support for running on both options.
Is that right, or have I missed something?
As I and the team I am a part of not only develop the application, but also pretty much do maintenance and setup of servers I don't see the value for us of being able to run on fastcgi, cgi, and mod_perl, we do just fine with just mod_perl.
Have I misunderstood the PSGI functionality, or is it just not suitable for my project?
Forget the Apache bit. It's a way of writing your application so that the choice of webserver becomes less relevant. At $work we switched to Plack/PSGI after finding our app running with very high CPU load after upgrading to Apache2 - benchmarking various Apache configs and NYTProf'ing were unable to determine the reason, and using PSGI and the Starman webserver worked out much better for us.
Now everything is handled in one place by our PSGI app (URL re-writes, static content, expiry headers, etc) rather than Apache configuration, so it's a) Perl, and b) easily tested via our standard /t/ scripts. Also our tests are now testing exactly what a user sees, rather than just the basic app itself.
It may well not be relevant to you if you're happy with Apache and mod_perl, and I'm sure others will be able to give much better answers, but for us not having to deal with anything Apache-related again is such a relief in itself. The ease of testing, and the ability to just stick in a Data::Dumper and see what's going on rather than wrestling with ModRewrite and friends, is a great boon.
Borrowing from a recent blog post by chromatic, Why PSGI/Plack Matters (Testing), here's what it is:
It's a good idea borrowed from Python's WSGI and Ruby's Rack but made Perlish; it's a simple formalizing of a pattern of web application development, where the entry point into the application is a function reference and the exit point is a tuple of header information and a response body.
That's it. That's as simple as it can be, and that simplicity deceives a lot of people who want to learn it.
An important benefit is, ibid.,
Given a Plack application, you don't have to deploy to a web server—even locally—to test your application as if it were deployed … Plack and TWMP (and Plack::Test) use the well-defined Plack pattern to make something which was previously difficult into something amazingly easy. They're not the first and they won't be the last, but they do demonstrate the value of Plack.
Started wrote an answer and after 50 lines I deleted it. Simply because it is impossible tell (in short) why is PSGI extremely cool. I'm new in PSGI too, but zilion things now are much easier as before in my apache/mod_perl era.
I can give you next advices:
read the Plack advent calendar - all days, step-by-step. You must understand the basic philosophy, what is good on onions and so on... :)
search CPAN for "Plack::Middleware::" - and read the first few lines in each. Here are MANY. (Really should be somewhere some short overview for each one, unfortunately don't know any faster way. Simply it is good to know, what middlewares are already developed. (For example, you sure will need the Plack::Middleware::Session, or Plack::Middleware::Static and so on...)
read about Plack::Builder (already done, when you done with the advent calendar) :)
try write some apps with it and will find than Plack is like the first sex - now you didn't understand that you could live without it.
ps:
If was here something like "Perl Oscar", will sure nominating MyiagavaSan. :)
I've been having an agruement with a friend that Mason (Perl) is not a framework, but a templating language. I feel Mason for Perl does what JSP does for Java (as an analogy, not pure technical comparison). From what I know, JSP is not a framework and I feel neither is Mason. When I looked up wikipedia Mason (Perl), I see that the main site says it is a web application framework written in Perl while the discussion page contests it.
Any pointers on why it is/ it is not a framework?
Update based on comments from ysth:
For a framework, I feel it should at least make db access easy, manage sessions, basic security that a webapp would need, templating and code reuse (or libraries that make basic tasks easy).
Mason is an 'M' short of being a MVC (Model-View-Controller) framework. It provides extensive rendering (View) features, which is why people think of Mason as being a templating language. However it also provides quite a few dispatch mechanisms (epsecially in the form of dhandlers), and control mechanisms (which fit naturally into autohandlers).
A few years ago I wrote an on-line tutorial (in Mason) to show off some of these features. It's optimised for full-screen display, and needs javascript enabled.
What Mason doesn't give you is a database abstraction layer, so you have to bring your own Model.
To the best of my knowledge amazon.com is written in Mason, along with many other sites.
If you enjoy working with Mason, but you'd like to have a Model, more toys, and a pony, then you may consider looking at Jifty as a web application framework.
A templating system would be something like HTML::Template, that is, a module that only does templating.
I feel that Mason does more, it has somehow a routing mechanism, it provides argument handling though %ARGS, intialisations through %INIT.
It also provides interfaces to mod_perl, CGI...
Now, it does not talk to the database, as if you want a clean way to do it, you'll have to use Class::DBI, DBIx::Perlish or one of the other hundred perl modules that does object mapping, or whatever else...
It is not an Model-View-Controller type of framework, it is probably closer to PHP than Ruby on Rails for example (and just as bad from what I have seen of it).
Can't answer the question to whether HTML::Mason is or isn't a framework without looking at it but I'm always happy with the following definition....
"a framework calls your program whereas your program calls a library"
Looking at Embedded Perl in HTML with Mason view of its competition, I'd say it is a template language. Otherwise Catalyst and Maypole would be on the list. Also, I think I read somewhere that you can use Mason as the View portion in a Catalyst application.
I guess I can see where you can use it like a framework, but it seems to be more complete if you view it as a template language.
Mason alone is not a framework it's just a template system BUT with some very cool features. It's got it's own structure and you can embed perl code very easely in it also it's got cache support. I've seen people who use Mason alone for developing a large application, but I guess it works better in an MVC framework.
Take care!
The following definition of a framework is taken from the Gamma book on Design Patterns. "A framework is a set of cooperating classes that make up a reusable design for a specific class of software." Mason, by that definition, is a framework. An MVC framework is only one type of framework.
HTML::Mason is what frameworks want to become when they get older. With HTML::Mason you get:
a dispatcher
templating
caching
logging
extremely flexible modularization
It was designed for high performance multi-tiered web applications, not for pleasing the fans of design patterns borrowed from desktop programming (such as MVC was).
Depends of your definition of framework.
You can apply name framework to any library if it does more than one thing.
A few years ago I did a lot of work with CGI.pm. I'm evaluating using it again for a quick project. Can someone bring me up to speed on the current state of developing with CGI.pm in the "Web 2.0" world? What are the best libraries on CPAN to use with it? Are there clean ways to include jQuery, YUI, other CSS libs, etc, and do some AJAX. There are of course lots of libraries on CPAN but what works and what is commonly used?
We aren't still doing this?
$JSCRIPT<<EOF;
...
EOF
I realize people are going to offer Catalyst as an answer. However, many people may have legacy CGI.pm apps they simply want to enhance. Is starting over really the best answer?
Personally, I'm no fan of Catalyst (too heavy for my taste) or Mason (mixing code and HTML is bad ju-ju), but I do quite well using CGI.pm for input[1], HTML::Template for output, and CGI::Ajax to provide AJAX functionality where called for.
If you're looking at frameworks, you may also want to consider CGI::Application, which is a widely-used and lighter-weight alternative to Catalyst/Mason.
[1] I can't recall the last time I called anything other than $q->param or $q->cookie from CGI.pm. There are still a lot of tutorials out there saying to use its HTML-generation functions, but that's still mixing code and HTML in a way that's just as bad as using here docs, if not worse.
Consider using something more modern, for example Catalyst. It will make your life much easier and you won't have to reinvent the wheel. I understand that it is just a small project, but from my experience many small projects in time become large ones :)
The "web 2.0" apps that I've worked with usually use client-side JavaScript to request JSON data from the server, then use that data to update the page in-place via DOM.
The JSON module is useful for returning structured data to a browser.
As far as including JavaScript, HTML, or whatever in a here doc - that was never a good idea, and still isn't. Instead, use one of the plethora of template modules to be found on CPAN. For a CGI, I'd avoid "heavy" modules like Mason or Template Toolkit, and use a lighter module for quicker startup, such as Text::Template, or Template::Simple.
Yes, you can write perfect web2.0 web applications WITHOUT using any framework on the server side in any language Perl, Python, Java, etc and WITHOUT using any JavaScript libraries/framework on the client side. The definition of web 2.0 is kind of a loose definition, and I'm guessing by web2.0, you mean Ajax or partial page refresh, then all you would really need is to focus on the following:
Know about the XmlHttpRequest object.
Know how to return JSON object from the server to the client.
Know how to safely evaluate/parse the JSON object using JavaScript and know to manipulate the DOM. Also, at least know about innerHTML. InnerHTML is helpful occasioanally.
Know CSS.
Having said that, it's a lot easier to use some framework on the server side, but not because it's required by web2.0 and it's a lot easier to use some JavaScript on the client like jQuery, mootools, YUI. And you can mix-and-match depends on your needs and your tastes. Most JavaScript provides wrapper around the XmlHttpRequest so that it works across all browsers. No one write "naked" XmlHttpRequest anymore, unless you want to show some samples.
It's perfectly possible to write "Web 2.0" apps using CGI.pm, but you'll have to do the work yourself. From what I've seen, the focus in the Perl development community has been on developing successor frameworks to CGI, not on writing helper modules to let legacy apps get bootstrapped into modern paradigms. So you're somewhat on your own.
As to whether to start over, what are you really trying to accomplish? Everyone's definition of "Web 2.0" is somewhat different.
If you're trying to introduce a few modern features (like AJAX) to a legacy app, then there's no reason you need to start over.
On the other hand if you're trying to write something that truly looks, feels, and works like a modern web app (for example, moving away from the page-load is app-state model), you should probably consider starting from the ground up. Trying to make that much of a transformation happen after the fact is going to be more trouble than it's worth for anything but the most trivial of apps.
I agree with Adam's answer, you probably want to use Catalyst. That being said, if you really don't want to, there's nothing preventing you from using only CGI.pm. The thing is, Catalyst is a collection of packages that do the things you want to make Web 2.0 easy. It combines the various templating engines such as Template Toolkit or Mason with the various ORM interfaces like DBIx::Class and Class::DBI.
Certainly you don't have to use these things to write Web 2.0 apps, it's just a good idea. Part of your question is wondering if javascript and CSS frameworks like jQuery, or prototype require anything from the server-side code. They don't, you can use them with any kind of server-side code you want.
For new apps, if you don't find Catalyst to your taste, Dancer is another lightweight framework you may like. There are also plenty of others, including CGI::Simple, Mojo/Mojolicious, Squatting...
Any of these lightweight frameworks can take care of the boring parts of web programming for you, and let you get on with writing the fun parts the way you want to.
If the jump from CGI.pm to Catalyst seems too daunting then perhaps something like Squatting might be more appropriate?
Squatting is a web microframework and I have found it ideal for quick prototyping and for replacing/upgrading my old CGI scripts.
I have recently built a small "web 2.0" app with Squatting using jQuery with no issues at all. Inside the CPAN distribution there is an example directory which contains some programs using jQuery and AJAX including a very interesting [COMET](http://en.wikipedia.org/wiki/Comet_(programming)) example which makes use of Continuity (which Squatting "squats" on by default).
NB. If required then you can later "squat" your app onto Catalyst with Squatting::On::Catalyst
There is also CGI::Ajax.
Every time I see Ruby or Python discussed in the context of web development, it's always with a framework (Rails for Ruby, Django for Python). Are these frameworks necessary? If not, is there a reason why these languages are often used within a framework, while Perl and PHP are not?
I can only speak towards Ruby - but, no, you don't need a framework to run Ruby based pages on the web. You do need a ruby enabled server, such as Apache running eruby/erb. But, once you do, you can create .rhtml files just like RoR, where it processes the inline ruby code.
The short answer is no, they are not necessary. In ruby you have .erb templates that can be used in a similar way as you use PHP pages. You can write a site in ruby or Python using several technologies (Rails-like frameworks, Templates or even talking directly with the HTTP library and building the page CGI-style).
Web frameworks like Python's Django or Ruby's Rails (there are many) just raise the level of abstraction from the PHP's or ASP's, and automate several process (like login, database interaction, REST API's) which is always a good thing.
"Need" is a strong word. You can certainly write Python without one, but I wouldn't want to.
Python wasn't designed (like PHP was, for example) as a direct web scripting language, so common web-ish things like connecting to databases isn't native, and frameworks are handy.
EDIT: mod_python exists for Apache, so if you're merely looking to write some scripts, then Python doesn't need a framework. If you want to build an entire site, I'd recommend using one.
From a Pythonic point of view, you'd absolutely want to use one of the frameworks. Yes, it might be possible to write a web app without them, but it's not going to be pretty. Here's a few things you'll (probably) end up writing from scratch:
Templating: unless you're writing a really really quick hack, you don't want to be generating all of your HTML within your Python code -- this is a really poor design that becomes a maintainability nightmare.
URL Processing: splitting a URL and identifying which code to run isn't a trivial task. Django (for example) provides a fantastic mechanism to map from a set of regular expressions to a set of view functions.
Authentication: rolling your own login/logout/session management code is a pain, especially when there's already pre-written (and tested) code available
Error handling: frameworks already have a good mechanism in place to a) help you debug your app, and b) help redirect to proper 404 and 500 pages.
To add to this, all of the framework libraries are all heavily tested (and fire tested). Additionally, there are communities of people who are developing using the same code base, so if you have any questions, you can probably find help.
In summary, you don't have to, but unless your project is "a new web framework", you're probably better off using one of the existing ones instead.
Framework? Heck, you don't even need a web server if you're using Python, you can make one in around three lines of code.
As to the why:
The most plausible thing I can think of is that Perl and PHP were developed before the notion of using frameworks for web apps became popular. Hence, the "old" way of doing things has stuck around in those cultures. Ruby and Python became popular after frameworks became popular, hence they developed together. If your language has a good framework (or more than one) that's well supported by the community, there's not much reason to try to write a Web App without one.
A framework isn't necessary per se, but it can certainly speed development and help you write "better" code. In PHP, there are definitely frameworks that get used like CakePHP, and in Perl there are many as well like Mason and Catalyst.
The frameworks aren't necessary. However, a lot of developers think frameworks ease development by automating a lot of things. For example, Django will create a production-ready backend for you based on your database structure. It also has lets you incorporate various plugins if you choose. I don't know too much about Rails or Perl frameworks, but PHP frameworks such as Zend, Symfony, Code Igniter, CakePHP, etc are used widely.
Where I work at we rolled our own PHP framework.
Are these frameworks necessary?
No. They, like any 'framework', are simply for speeding up development time and making the programmer's job easier.
If not, is there a reason why these languages are often used within a framework, while Perl and PHP are not?
PHP and Perl were popular languages for building web sites well before the idea of using frameworks was. Frameworks like Rails are what gave Ruby it's following. I'm not sure that Python or Ruby were that common as web languages before they were backed by frameworks.
These days, even PHP/Perl web developement should be backed by a framework (of which there are now many).
By no means are those development frameworks required. But as with most development environments, your productivity will increase exponentially if you have a supported framework to reference and build your applications on. It also decreases the training needed to bring others up to speed on your applications if they already have a core understanding of the framework that you use.
For python, the answer is No you don't have to. You can write python directly behind your web server very easily, take a look at mod_python for how to do it.
A lot of people like frameworks because they supply a lot of the boilerplate code in a reliable form so you don't have to write it yourself. But, like any code project, you should choose the tools and frameworks on their merit for your problem.
You can certainly write CGI scripts in either language and do things "raw".
The frameworks (ideally) save the trouble of writing a pile of code for things that other people have already handled (session handling, etc.).
The decision probably comes down to what you need to do. If the framework has the features you need, why not use it. If the framework is going to require extensive modifications, it might be easier to roll your own stuff. Or check out a different framework.
The python library has numerous modules for doing cgi, parsing html, cookies, WSGI, etc:
http://docs.python.org/library/index.html
PHP has a lot of frameworks. Probably more then most. In Ruby most use Rails so thats what you hear, and Django for Python is mentioned more then not.
But with PHP you have many to choose from.
List of web application frameworks
Any language that can "print" can be used to generate web pages, but frameworks handle a lot of the HTML generation for you. They let you concentrate more on the content and less on the details of coding the raw HTML.