Catalyst::Manual::TutoUser:Contributed)Catalyst::Manual::Tutorial::01_Intro(3)NAMECatalyst::Manual::Tutorial::01_Intro - Catalyst Tutorial - Chapter 1:
Introduction
OVERVIEW
This is Chapter 1 of 10 for the Catalyst tutorial.
Tutorial Overview
1. 01_Introduction
2. Catalyst Basics
3. More Catalyst Basics
4. Basic CRUD
5. Authentication
6. Authorization
7. Debugging
8. Testing
9. Advanced CRUD
10. Appendices
DESCRIPTION
This tutorial provides a multi-part introduction to the Catalyst Web
Framework. It seeks to provide a rapid overview of many of its most
commonly used features. The focus is on the real-world best practices
required in the construction of nearly all Catalyst applications.
Although the primary target of the tutorial is users new to the
Catalyst framework, experienced users may wish to review specific
sections (for example, how to use DBIC for their model classes, how to
add authentication and authorization to an existing application, and/or
form management).
The most recent code for the tutorial is included on the Tutorial
Virtual Machine you can download from:
<http://cattut.shadowcat.co.uk/>
See "STARTING WITH THE TUTORIAL VIRTUAL MACHINE" below for instructions
getting and using the VM.
Should you wish to download the code directly, you get pull it via the
following command (note: will probably be switching to git soon):
svn co http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/Tutorial/ CatalystTutorial
This will download the most recent code for each chapter of the
tutorial into the CatalystTutorial directory on your machine.
These reference implementations are provided so that when you follow
the tutorial, you can use the code to ensure that your system is set up
correctly (which shouldn't be an issue if you use the Tutorial Virtual
Machine), :-) and that you have not inadvertently made any typographic
errors, or accidentally skipped part of the tutorial.
NOTE: You can use any Perl-supported OS and environment to run
Catalyst. It should make little or no difference to Catalyst's
operation, but this tutorial has been written using the Debian-based
Tutorial Virtual Machine that you can download and use to work through
the full tutorial step by step. WE STRONGLY RECOMMEND THAT YOU USE THE
VIRTUAL MACHINE IMAGE TO WORK THROUGH THE TUTORIAL to avoid issues that
may crop up if you are working with a different configuration. We have
tested the Tutorial Virtual Machine to make sure all of the examples
work correctly, but it is hard to guarantee this on other platforms and
versions.
If you would prefer to install directly from CPAN and not use the
Tutorial Virtual machine, you can download the example program and all
the necessary dependencies to your local machine by installing the
"Task::Catalyst::Tutorial" distribution:
cpan Task::Catalyst::Tutorial
This will also test to make sure the dependencies are working. If you
have trouble installing these, please ask for help on the #catalyst IRC
channel, or the Catalyst mailing list.
Subjects covered by the tutorial include:
· A simple application that lists and adds books.
· The use of DBIx::Class (DBIC) for the model (including some of the
more advanced techniques you will probably want to use in your
applications).
· How to write CRUD (Create, Read, Update, and Delete) operations in
Catalyst.
· Authentication ("auth").
· Role-based authorization ("authz").
· Attempts to provide an example showing current (5.9) Catalyst
practices.
· The use of Template Toolkit (TT).
· Useful techniques for troubleshooting and debugging Catalyst
applications.
· The use of SQLite as a database (with code also provided for MySQL
and PostgreSQL). (Note: Because we make use of the DBIx::Class
Object Relational Mapping [ORM] layer, out our application will be
database agnostic and can easily be used by any of the databases
supported by DBIx::Class.)
· The use of HTML::FormFu or HTML::FormHandler for automated form
processing and validation.
This tutorial makes the learning process its main priority. For
example, the level of comments in the code found here would likely be
considered excessive in a "normal project." Because of their
contextual value, this tutorial will generally favor inline comments
over a separate discussion in the text. It also deliberately tries to
demonstrate multiple approaches to various features (in general, you
should try to be as consistent as possible with your own production
code).
Furthermore, this tutorial tries to minimize the number of controllers,
models, TT templates, and database tables. Although this does result
in things being a bit contrived at times, the concepts should be
applicable to more complex environments. More complete and complicated
example applications can be found at
<http://wiki.catalystframework.org/wiki/resources/catalystexamples> and
in the "examples" area of the Catalyst Subversion repository at
<http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/>.
STARTING WITH THE TUTORIAL VIRTUAL MACHINE
The steps below briefly outline how you can download the Tutorial
Virtual Machine. This document uses the term "host machine" to refer
to the physical machine where you will run the virtualization software
and boot up the VM. The terms "guest machine" or just "VM" refer to
the virtual machine itself -- the thing where you actually do the
tutorial (and that you boot up on the "host machine").
Note: Throughout the tutorial, we will shows the UNIX shell prompt as
""$"". If you are using the Tutorial VM, the prompt will really be
""catalyst@catalyst:~$"" (where ""~"" will change to show your current
directory), but we will keep it short and just use ""$"".
1. Download a Tutorial Virtual Machine image from
<http://cattut.shadowcat.co.uk/>
A big thanks to Shadowcat Systems for hosting the virtual machines
(and everything else they do for the Perl community)!
2. Uncompress the image on the "host machine":
MAINCOMPUTER:~$ tar zxvf CatalystTutorial.tgz
3. Boot the virtual machine using a tool like VMWare Player
<http://www.vmware.com/products/player> or VirtualBox
<http://www.virtualbox.org/>.
4. Once you get a login prompt, enter the username catalyst and a
password for "catalyst". You should now be at a prompt that looks
like:
catalyst login: catalyst
Password: catalyst
...
catalyst@catalyst:~$
5. Type ""ifconfig"" to get the IP address assigned to the virtual
machine. You should get output along the lines of:
eth0 Link encap:Ethernet HWaddr 00:01:22:3b:45:69
inet addr:192.168.0.12 Bcast:192.168.0.255 Mask:255.255.255.0
...
You want the IP address on the second line below the "eth0"
interface. The image it design to automatically use a DHCP-
assigned address.
Try to ping this IP address from your "host machine" (main
desktop):
MAINCOMPUTER:~$ ping 192.168.0.12
PING 192.168.0.12 (192.168.0.12) 56(84) bytes of data.
64 bytes from 192.168.0.12: icmp_req=1 ttl=255 time=4.97 ms
64 bytes from 192.168.0.12: icmp_req=2 ttl=255 time=3.43 ms
...
Note: The ping above is being originated from your host machine
(main desktop) and going to your guest virtual machine, not the
other way around.
If you are not seeing a valid IP address or it's not responding to
pings (for example, you get error messages along the lines of
"Request timed out", "100% packet loss", or "Destination Host
Unreachable"), there could be a few network-related issues you
might need to sort out. See the section below "Sorting Out Virtual
Machine Network-Related Issues" for additional information and
troubleshooting advice.
Note: Remember this IP address... you will be using it throughout
the tutorial.
6. From your main desktop machine, open an SSH client and connect to
the IP address found in the previous step. You should get a login
prompt (accept the SSH key if you get a warning message about
that). Login with the same username and password as we used in
Step 4: catalyst / catalyst
catalyst login: catalyst
Password: catalyst
...
catalyst@catalyst:~$
7. Using the SSH session, change to the sample code directory for
Chapter 3 included with the Tutorial Virtual Machine and start the
Catalyst Development Server:
$ cd Final/Chapter03/MyApp
$ perl scripts/myapp_server
8. From your main desktop machine (the "host machine"), open a web
browser and go to http://A.B.C.D:3000/, where "A.B.C.D" is the IP
address to your virtual machine that you looked up in Step 5. For
example, if your virtual machine is using the IP address
192.168.0.12, you would put the following URL into your web
browser:
http://192.168.0.12:3000/
Make sure you don't forget the :3000 to use port 3000 instead of
the usual port 80 that is used by HTTP by default.
You should get a Catalyst Welcome Screen. If you do, feel free to
jump right in to Chapter 2 of the tutorial. If you don't go get
the Catalyst Welcome Screen, go back and carefully check each of
the steps above.
9. Optional: Also, to reduce download size, the Tutorial VM just
includes a minimal command-line environment. You are free to use
Debian's very capable "apt" package manager to install other
packages. You will first want to pull the apt cache files with
"aptitude update" (or "apt-get update" if you prefer apt-get).
The VI/VIM editor is already installed on the Tutorial Virtual
Machine. In order to reduce the size of the download, Emacs is not
pre-installed. Since people obviously have very strong opinions
about which editor is best, :-) fortunately it's very easy to
install Emacs:
$ sudo aptitude update
$ sudo aptitude install emacs
In general, it is expected that people will boot up the Tutorial VM
on their main desktop (the "host machine" using the terminology
above) and then use that main desktop machine to SSH and web browse
into the "guest VM" as they work through the tutorial. If you wish
to install X Windows (or any other packages), just use the
"aptitude" (or "apt-get") Debian commands.
For example, to install X Windows with Fluxbox (a lightweight
WindowManager -- it is great for things like this tutorial since
it's about 1/10th the size of other common X Windows environments),
you can do:
$ sudo aptitude update
$ sudo aptitude install xorg fluxbox iceweasel
And then start X Windows from the VM Console with this command:
$ startx
Note that if you want to start Fluxbox from an SSH session, you can
use the "sudo dpkg-reconfigure x11-common" and select "anybody"
from the menu. Otherwise, you will need to be on the actual "VM
console" to start it.
If you have a preference for the Gnome desktop environment, you can
do:
$ sudo aptitude update
$ sudo ptitude install gnome iceweasel
$
$ # You can reboot or start with 'startx', we will just reboot here
$ reboot
$ sudo aptitude install kde iceweasel
For KDE, just substitude the package name ""kde"" for ""gnome""
above.
Note that "iceweasel" is basically used to install Firefox on
Debian boxes. You can start it under X Windows with either the
"firefox" command or the "iceweasel" command (or use the menus).
You can get more information on Iceweasel at
<http://wiki.debian.org/Iceweasel>.
Also, you might need to add more memory to your virtual machine if
you want to run X Windows (or other tools that might require
additional memory). Consult the documentation for you
virtualization software for instructions on how to do this (it's
usually pretty simple).
You may note that the Tutorial Virtual Machine uses local::lib so that
the Perl modules are run from ~/perl5 (in this case,
/home/catalyst/perl5) vs. the usual location of your "system Perl". We
recommend that you also consider using this very handy module. It can
greatly ease the process of maintaining and testing different
combinations or Perl modules across development, staging, and
production servers. (The "relocatable Perl" feature can also be used
to to run both the modules and Perl itself from your home directory [or
any other directory you chose]).
Note: Please provide feedback on how the Virtual Machine approach for
the tutorial works for you. If you have suggestions or comments, you
can reach the author through the email address at the bottom of this
page or via an RT ticket at
https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual
<https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
Sorting Out Virtual Machine Network-Related Issues
In general, using a virtual machine to work through the tutorial is
*much* easier than trying to do it in other environments, especially if
you are new to Catalyst (or Perl or CPAN or ...). However, it's
possible that you could run into a few network-related issues. The
good news is that there is lots of information about the issue
available via search engines on the Internet. Here is some background
information to get you started.
In Step 5 of the prior section above, we assumed that a "Bridged Mode"
configuration and DHCP will work (it should for most people). If DHCP
is not working or is not available in your location, most virtual
machine "host" environments let you select between one of several
different types of networking between the "guest" and the "host"
machine.
1) Bridged
2) NAT
3) Local host only
The Tutorial Virtual Machine defaults to "Bridged" -- this should
result in the VM acting like another device on your network that will
get a different DHCP IP address than the host machine. The advantage
of this approach, is that you can easily SSH and web browse to the
guest virtual machine. In general, this is the best option if you want
to be able to boot up the VM and then use your SSH client and web
browser from your main machine to connect into the virtual machine.
In some environments, you might have better luck with "NAT" (Network
Address Translation) mode. With this configuration, the guest VM
shares the same IP address as the host machine. The downside of this
approach is that special configuration is required if you want to be
able to SSH or web browse to the guest VM. The NAT option should
automatically allow the VM "outbound connection" (e.g., to the Internet
if you want to install additional Debian packages), but it requires
special configuration if you want to get "inbound connections" that go
from some other machine (including the "host machine") into the VM.
Some virtual machine host environments let you configure a "static NAT"
or "port forwarding" to reach the guest OS, but others omit this
functionality.
Note: NAT mode can work fine if you install X Windows and do the whole
tutorial locally on the actual VM vs. using SSH and a web browser from
your host machine.
"Local host only" mode let's the guest VM and the host machine talk on
a "private subnet" that other devices in your network cannot reach.
This can work as long as you don't need to go from the VM to the
Internet (for example, to install other Debian packages).
Consult the documentation on your virtual machine host environment for
help configuring the options above. Here are some links that might
help:
· <http://vmfaq.com/entry/34/>
· <http://www.vmware.com/support/pubs/player_pubs.html>
· <http://www.virtualbox.org/manual/ch06.html>
VERSIONS AND CONVENTIONS USED IN THIS TUTORIAL
This tutorial was built using the following resources. Please note that
you may need to make adjustments for different environments and
versions (note that trailing zeros in version numbers are not
significant and may get dropped with some techniques for viewing them;
for example, Catalyst v5.80020 might show up as 5.8002):
· Debian 6 (Squeeze)
· Catalyst v5.90002
· Catalyst::Devel v1.34
· DBIx::Class v0.08195
· Catalyst::Model::DBIC::Schema v0.54
· Template Toolkit v2.22
· HTML::FormFu -- v0.09004
· NOTE: You can check the versions you have installed with the
following command (note the slash before the space):
perl -M<_mod_name_>\ 999
or:
perl -M<_mod_name_> -e 'print "$<_mod_name_>::VERSION\n"'
For example:
perl -MCatalyst::Devel\ 999
or:
perl -MCatalyst::Devel -e 'print "$Catalyst::Devel::VERSION\n";'
· This tutorial will show URLs in the format of
"http://localhost:3000", but if you are running your web browser
from outside the Tutorial Virtual Machine, you will want to
substitute the IP address of your VM for the "localhost" in the
URLs (again, you can get the IP address for eth0 from the
"ifconfig" command). For example, if your VM has an IP address of
192.168.0.12, you will want to use a base URL of
"http://192.168.0.12:3000". Note that the development server
defaults to port 3000 (you can change with with the "-p" option on
the command line.
Please Note: Depending on the web browser you are using, you might
need to hit "Shift+Reload" or "Ctrl+Reload" to pull a fresh page
when testing your application at various points (see
<http://en.wikipedia.org/wiki/Wikipedia:Bypass_your_cache> for a
comprehensive list of options for each browser).
Also, the "-k" keepalive option to the development server can be
necessary with some browsers (especially Internet Explorer).
DATABASES
This tutorial will primarily focus on SQLite because of its simplicity
of installation and use; however, modifications in the script required
to support MySQL and PostgreSQL will be presented in the Appendix.
Note: One of the advantages of using tools like Catalyst and DBIC is
that applications become much more database independent. As such, you
will notice that only the ".sql" files used to initialize the database
change between database systems: most of the code generally remains the
same.
You can jump to the next chapter of the tutorial here: Catalyst Basics
AUTHOR
Kennedy Clark, "hkclark@gmail.com"
Feel free to contact the author for any errors or suggestions, but the
best way to report issues is via the CPAN RT Bug system at
https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual
<https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
Copyright 2006-2011, Kennedy Clark, under the Creative Commons
Attribution Share-Alike License Version 3.0
(http://creativecommons.org/licenses/by-sa/3.0/us/
<http://creativecommons.org/licenses/by-sa/3.0/us/>).
perl v5.14.22012-Catalyst::Manual::Tutorial::01_Intro(3)