i have a big web application running in perl CGI. It's running ok, it's well written, but as it was done in the past, all the html are defined hardcoded in the CGI calls, so as you could imagine, it's hard to mantain, improve and etc. So now i would like to start to add some templating and integrate with a framework (catalyst or CGI::application). My question is: Somebody here has an experience like that? There is any things that i must pay attention for? I'm aware that with both frameworks i can run native CGI scripts, so it's good because i can run both (CGI native ad "frameworked" code) together without any trauma. Any tips?
Write tests first (for example with Test::WWW::Mechanize). Then when you change things you always know if something breaks, and what it is that breaks.
Then extract HTML into templates, and commonly used subs into modules. After that it's a piece of cake to switch to a framework.
In general, go step by step so that you always have a working application.
Extricate the HTML from the processing logic in the CGI script. Identify all code that affects the HTML output, as these are candidates for becoming template variables. Separate that into a HTML file, with the identified parts marked with template variables. Eventually you will be able to refactor the page such that all processing is done at the start of the code and the HTML template just called up at the end of all processing.
In this kind of situation, rewriting from scratch basically, the old code is useful for A) testing, and B) design details. Ideally you'd make a set of tests, for all the basic functionality that you want to replicate, or at least tests that parse the final result pages so you can see the new code is returning the same information for the same inputs.
Design details within the code might be useless, depending on how much the framework handles automatically. If you have a good set of tests, and a straightforward conversion works well, you're done. If the behavior of the new doesn't match the old, you probably need to dig deeper into the "why?" and that'll probably be something odd looking, that doesn't make sense at first glance.
One thing to remember to do first is, find out if anyone has made something similar in the framework you're using. You could save yourself a LOT of time and money.
Here is how I did it using Python instead of Perl, but that should not matter:
Separated out HTML and code into distinct files. I used a template engine for that.
Created functions from the code which rendered a template with a set of parameters.
Organized the functions (which I termed views, inspired by Django) in a sensible way. (Admin views, User views, etc.) The views all follow the same calling convention!
Refactored out the database and request stuff so that the views would only contain view specific code (read: Handling GET, POST requests, etc. but nothing low-level!). Relied heavily on existing libraries for that.
I am here at the moment. :-) The next obvious step is of course:
Write a dispatcher which maps URLs to your views. This will also lead to nicer URLs and nicer 404- and error handling of course.
One of the assumptions that frameworks make is that the urls map to the code. For example in a framework you'll often see the following:
http://app.com/docs/list
http://app.com/docs/view/123
Usually though the old CGI scripts don't work like that, you're more likely to have something like:
http://app.com/docs.cgi?action=view&id=123
To take advantage of the framework you may well need to change all the urls. Whether you can do this, and how you keep old links working, may well form a large part of your decision.
Also frameworks provide support for some sort of ORM (object relational mapper) which abstracts the database calls and lets you only deal with objects. For Catalyst this is usually DBIx::Class. You should evaluate what the cost of switching to this will be.
You'll probably find that you want to do a complete rewrite, with the old code as a reference platform. This may be much less work than you expect. However start with a few toy sites to get a feel for whichever framework/orm/template you decide to go with.
Related
I've been a heavy Windsor users for the last several years. Prior to the Fluent Registration API, I would toggle between Xml Registration and huge piles of AddComponent() code. We've been happily using the Fluent Registration API and Installers specifically for quite some time now. I've gotten the impression from various writings like this:
http://docs.castleproject.org/Windsor.XML-Registration-Reference.ashx
That the Xml Registration approach has fallen out of favor and it wouldn't surprise me if it were marked for deprecation at some point in the near future.
Now, for my question: The Fluent Registration API and Installers work swimmingly for auto-wiring scenarios (i.e. when I want Windsor to just figure out how to construct my object graphs). Auto-wiring is the vast majority of IoC use cases out there, but what about when auto-wiring isn't possible? In other words I have multiple implementations of a service and I need to tell Windsor how to construct parts of my object graph. I've done this many times with the Xml Registration approach, but is there a more preferred approach these days? I'm hesitant to go the Xml Registration approach as its future seems uncertain, but I don't know how else to accomplish this with Windsor.
My uses cases are:
System needs to be able to swap implementations at QA-test (i.e.
credit checks and fraud detection processing where we want to test
without a dependency on a credit bureau API)
Provider patterns in our
system where we need to conditionally turn on and off different
implementations at deploy-time.
This all seems very well suited for IoC and we have all the building blocks in place, but want to make sure I'm taking the most future-proof approach with Windsor.
UPDATE:
While I like the feature toggle approach, I recently discovered a Windsor feature that is very useful on this front - Fallback Components. I'm leaving this edit here for anyone that might stumbled across this later.
Configuring your DI container completely through XML is error prone, verbose, and just too painful. The XML configuration possibilities are always a subset of what you can do with code based configuration; code is always more expressive.
Sometimes though your DI configuration depends on deploy-time configurations, but since the number of knobs you need are often fairly small, using a configuration flag is often a much better approach than polluting your configuration file with fully qualified type names.
Or let me put it differently, when you have large amounts of your DI configuration placed in your configuration file because your might want to change them at deploy time, please think again. Many of the changes need testing (by a developer) anyway, so there is no way you want someone from your operations team to fiddle around with that. And when you need a developer to look at it and verify it, what's the advantage of not having to recompile the project? Is this actually any quicker? A developer would still have to start the application anyway.
It is a false sense of flexibility and in fact a poor interface design (xml is the interface for your maintenance and operations department). BTW, are you the person that needs to document how the configuration file should be changed?
Instead of describing the list of fully qualified type names that are valid somewhere in the middle of the xml file, wouldn't it be much easier of all you have to write is "place 'false' in this field to disable ..."?
Here is an example of how to use a configuration switch:
bool detectFraught =
ConfigurationManager.AppSettings["DetectFraud"] != "false";
container.Register(
Component.For(typeof(IFraughtDetector)).ImplementedBy(
detectFraught ? typeof(RealDectector) : typeof(FakeDetector));
See how the configuration switch is now simply a boolean flag. This makes the configuration file much more maintainable, since the configuration is now a simple boolean switch instead of a complete type name (that can be misspelled).
Of course doing the ["DetectFraud"] != "false" isn't that nice by itself, but this can simply be solved by creating a strongly-typed configuration helper.
This answer might help as well. Allows you to dynamically, at runtime, provide an implementation. Though, sounds like you don't need it that dynamically and it's a little less obvious what's going on.
There are no plans to obsolete or remove the XML config support in Windsor.
Yes, you are right, it isn't a preferred approach due to its numerous drawbacks.
Anything you can do in XML can be done in code (note that inverse is not true).
Also keep in mind XML is not all-or-nothing. There are many ways to achieve the scenarios you gave as examples without resorting to registration in XML.
Feature toggles
Conditional compilation
if/else in your installer based on a appSettings flag
others...
I've used each of them in different projects in the past.
I learn best by taking apart something that already does something and figuring out why decisions were made in which manner.
Recently I've started working with Perl's CGI::Application framework, but found i don't really get along well with the documentation (too little information on how to best structure an application with it). There are some examples of small applications on the cgi-app website, but they're mostly structured such that they demonstrate a small feature, but contain mostly of code that one would never actually use in production. Other examples are massively huge and would require way too much time to dig through. And most of them are just stuff that runs on cgiapp, but isn't open source.
As such I am looking for something that has most base functionality like user logins, db access, some processing, etc.; is actually used for something but not so big that it would take hours to even set them up.
Does something like that exist or am i out of luck?
CGI::Application tends to be used for small, rapid-development web applications (much like Dancer, Maypole and other related modules). I haven't seen any real examples of open-source web apps built on top of it, though perhaps I'm not looking hard enough.
You could look at Catalyst. The wiki has a list of Catalyst-powered software and there are a large number of apps there - poke around, see if you like the look of the framework. Of this, this is Perl, so some of those apps will be using Template::Toolkit, some will use HTML::Mason... still, you'll get a general idea.
Try looking at Miril CMS. Although I don't know in which state it is.
I am the same with code, and had the same request. When I did not find a solution I created my own. which is https://github.com/alexxroche/Notice
I hope that it is a good solution to this request.
Notice demonstrates:
CGI::Application
CGI::Application::Plugin::ConfigAuto
CGI::Application::Plugin::AutoRunmode
CGI::Application::Plugin::DBH
CGI::Application::Plugin::Session;
CGI::Application::Plugin::Authentication
CGI::Application::Plugin::Redirect
CGI::Application::Plugin::DBIC::Schema
CGI::Application::Plugin::Forward
CGI::Application::Plugin::TT
It comes with an example mysql schema, but because of DBIC::Schema it can be used with PostgreSQL, (or anything else that DBIx::Class supports.)
I use Notice in all of my real life applications since 2007. The version in github is everything except the branding and the content.
Check out the Krang CMS.
I've been trying to find a good form of RPC to standardize on, but so far I've ran into a ton of walls and was wondering what the stackoverflow communities view was.
My ideal RPC would provide the following:
Somewhat wide support in other languages, in that people shouldn't have to write a custom stack to use our server
Input validation
Ideally, some way to turn the above input validation into some sort of automated documentation to distribute
Clean and maintainable code
I am a fan of the catalyst framework and would prefer to stick to it, but if there is a clearly better alternative for RPC servers I'd be open to that as well.
So far I have looked at the following:
Catalyst::Controller::SOAP
Doesn't appear to support returning of complex data structures, only string('literals'). I could probably serialize data on top of that, but that seems very hacky. It also lets you return a pre-formed XML object, but I couldn't get that to work and it looks like you'd need to re-create a lot of SOAP data structure for it to work.
I do like the idea of WSDLs, but the complexity of the overall spec also makes me wonder how well support for communicating with other languages will be.
Custom POSTing XML based controller
We tried to roll our own by hand in a similar way to how we've seen two other projects do it recently where there is a dispatch url that you post XML to. This lets you have XSD validation/documentation, but required creating a lot more code than we want to maintain at this point.
Catalyst::Plugin::Server::XMLRPC
Gave a warning about using a deprecated method that will be removed in a future version of Catalyst.
No input validation or doc creation, but otherwise the best I've found
JSONRPC
Looks pretty similar to XMLRPC only the module is actually updated. I'll probably go with this next unless someone suggests something better
There also appears to be two different modules for catalyst that do JSONRPC
I realize that REST isn't pure RPC (only a subset), but...
I would recommend the Catalyst::Controller::REST and Catalyst::Action::REST modules. They're frequently updated and the documentation is fairly good. There is also a good (but rather dated) example of using Catalyst::Controller::Rest in the 2006 Catalyst Advent calendar titled Day 9 - Web Services with Catalyst::Action::REST.
FWIW, Catalyst::Controller::SOAP does support returning complex data. Take a look at the documentation http://search.cpan.org/~druoso/Catalyst-Controller-SOAP-1.23/lib/Catalyst/Controller/SOAP.pm, which will show you that you can use a WSDL to describe your service. Also, see http://daniel.ruoso.com/categoria/perl/soap-today.html.en for a more detailed step-by-step process.
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 example I've seen of CGI/Perl basically a bunch of print statements containing HTML, and this doesn't seem like the best way to write a CGI app. Is there a better way to do this? Thanks.
EDIT: I've decided to use CGI::Application and HTML::Template, and use the following tutorial: http://docs.google.com/View?docid=dd363fg9_77gb4hdh7b. Thanks!
Absolutely (you're probably looking at tutorials from the 90s). You'll want to pick a framework. In Perl-land these are the most popular choices:
CGI::Application - very lightweight with lots of community plugins
Catalyst - heavier with more bells and whistles
Jifty - more magical than the above
This is a really, really big question. In short, the better way is called Model/View/Controller (aka MVC). With MVC, your application is split into three pieces.
The Model is your data and business logic. It's the stuff that makes up the core of your application.
The View is the code for presenting things to the user. In a web application, this will typically be some sort of templating system, but it could also be a PDF or Excel spreadsheet. Basically, it's the output.
Finally, you have the Controller. This is responsible for putting the Model and View together. It takes a user's request, gets the relevant model objects, and calls the appropriate view.
mpeters already mentioned several MVC frameworks for Perl. You'll also want to pick a templating engine. The two most popular are Template Toolkit and Mason.
Leaving the question of CGI vs MVC framework for the moment, what you're going to want is one of the output templating modules from the CPAN.
The Template Toolkit is very popular (Template.pm on CPAN)
Also popular are Text::Template, HTML::Template, and HTML::Mason.
HTML::Mason is much more than a template module, and as such might be a little too heavy for a simple CGI app, but is worth investigating a little while you're deciding which would be best for you.
Text::Template is reasonably simple, and uses Perl inside the templates, so you can loop over data and perform display logic in Perl. This is seen as both a pro and con by people.
HTML::Template is also small and simple. It implements its own small set of tags for if/then/else processing, variable setting, and looping. That's it. This is seen as both a pro and a con for the exact opposite reasons as Text::Template.
Template toolkit (TT) implements a very large, perlish template language that includes looping and logic, and much more.
I used HTML::Template one, and found I wanted a few more features. I then used Text::Template with success, but found its desire to twiddle with namespaces to be a little annoying. I've come to know and love Template Toolkit. For me it just feels right.
Your mileage may vary.
Of course, there is still the old "print HTML" method, sometimes a couple of print statements suffices. But you've hit upon the idea of separating your display from your main logic. Which is a good thing.
It's the first step down the road to Model/View/Controller (MVC) in which you keep separate your data model&business logic (your code that accepts the input, does something with it, and decides what needs to be output), your your input/output (Templates or print statements - HTML, PDF, etc.) , and the code that connects the two (CGI, CGI::Application, Catalyst MVC Framework, etc.). The idea being that a change to your data structure (in the Model) should not require changes to your output routines (View).
The Perl5 Wiki provides a good (though not yet complete) list of web frameworks & templates.
The comparison articles linked in the "templates" wiki entry is worth reading. I would also recommend reading this push style templating systems article on PerlMonks.
For templating then Template Toolkit is the one I've used most and can highly recommend it. There is also an O'Reilly book and is probably the most used template system in the Perl kingdom (inside or outside of web frameworks).
Another approach which I've been drawn more and more to is non template "builder" solutions. Modules like Template::Declare & HTML::AsSubs fit this bill.
One solution that I feel strikes the right balance in the Framework/Roll-your-own dilemma is the use of three key perl modules: CGI.pm, Template Toolkit , and DBI. With these three modules you can do elegant MVC programming that is easy to write and to maintain.
All three modules are very flexible with Template Toolkit (TT) allowing you to output data in html, XML, or even pdf if you need to. You can also include perl logic in TT, even add your database interface there. This makes your CGI scripts very small and easy to maintain, especially when you use the "standard" pragma.
It also allows you to put JavaScript and AJAXy stuff in the template itself which mimics the separation between client and server.
These three modules are among the most popular on CPAN, have excellent documentation and a broad user base. Plus developing with these means you can rather quickly move to mod_perl once you have prototyped your code giving you a quick transition to Apache's embedded perl environment.
All in all a compact yet flexible toolset.
You can also separate presentation out from code and just use a templating system without needing to bring in all the overhead of a full-blown framework. Template Toolkit can be used by itself in this fashion, as can Mason, although I tend to consider it to be more of a framework disguised as a templating system.
If you're really gung-ho about separating code from presentation, though, be aware that TT and Mason both allow (or even encourage, depending on which docs you read) executable code to be embedded in the templates. Personally, I feel that embedding code in your HTML is no better than embedding HTML in your code, so I tend to opt for HTML::Template.