PerlSetVar MasonCompRoot /usr/local/www/htdocs
PerlSetVar MasonDataDir /usr/local/www/mason
PerlModule HTML::Mason::ApacheHandler
<FilesMatch "*.html">
SetHandler perl-script
PerlHandler HTML::Mason::ApacheHandler
</FilesMatch>
Mason's various pieces revolve around the notion of ``components''. A component is a mix of HTML, Perl, and special Mason commands, one component per file. So-called ''top-level`` components represent entire web-pages, while smaller components typically return HTML snippets for embedding in top-level components. This object-like architecture greatly simplifies site maintenance: change a shared component, and you instantly changed all dependant pages that refer to it across a site (or across many virtual sites).
Mason's component syntax lets designers separate a web page into programmatic and design elements. This means the esoteric Perl bits can be hidden near the bottom of a component, preloading simple variables for use above in the HTML. In our own experience, this frees content managers (i.e., non-programmers) to work on the layout without getting mired in programming details. Techies, however, still enjoy the full power of Perl.
One of the best ways to learn about Mason is to explore the samples/ directory created during installation. There you will find a collection of components, simple to complex, illustrating most of Mason's component syntax.
Other Mason features include:
Consider this simple Mason component:
% my $noun = 'World';
Hello <% $noun %>!
How are ya?
The output of this component is:
Hello World!
How are ya?
In this component you see a mix of standard HTML and Mason elements. The bare '%' prefixing the first line tells Mason that this is a line of Perl code. One line below, the embedded <% ... %> tag gets replaced with the return value of its contents, evaluated as a Perl expression.
Beyond this trivial example, components can also embed serious chunks of Perl code (say, to pull records from a database). They can also call other components, cache results for later reuse, and perform all the tricks you expect from a regular Perl program. See HTML::Mason::Devel for a full tutorial on building, using and debugging Mason components.
Mason has a standard MakeMaker-driven installation. See the README file for details.
The simplest configuration of Mason requires a few lines in your
httpd.conf. You can find an annotated version of these lines in
eg/httpd.conf in your distribution.
PerlSetVar MasonCompRoot /usr/local/www/htdocs
PerlSetVar MasonDataDir /usr/local/www/mason
PerlModule HTML::Mason::ApacheHandler
<FilesMatch "*.html">
SetHandler perl-script
PerlHandler HTML::Mason::ApacheHandler
</FilesMatch>
The first directive specifies the component root, the top of your component source tree. In simple configurations this is the same as your DocumentRoot.
The second directive specifies the data directory, where Mason maintains various subdirectories and data files at runtime. Mason will create this directory on startup if necessary.
The third directive loads Mason with Apache support. Mason must be
installed somewhere in your Perl @INC for this to work.
Finally, the <FilesMatch> section routes all ``*.html'' requests to the Mason handler. If you want all Mason pages to have a distinct extension like ``.mcomp'', use that instead. If you wish to restrict Mason to one subdirectory at first, do this:
<Directory /path/to/subdirectory>
<FilesMatch "*.html">
SetHandler perl-script
PerlHandler HTML::Mason::ApacheHandler
</FilesMatch>
</Directory>
Once you have added the configuration directives, restart the server. First, go to a standard URL on your site to make sure you haven't broken anything. If all goes well you should see the same page as before. If not, recheck your Apache config files and also tail your server's error log.
If you are getting ``404 Not Found'' errors even when the files clearly exist, Mason may be having trouble with your document and component root. One situation that will unfortunately confuse Mason is if your document or component root goes through a symbolic link. Try expressing both your document and component root in terms of the true filesystem path.
Next, try adding the tag <% 2+2 %> at the top of some HTML file. If you reload this page and see a ``4'', Mason is working!
Whoever is responsible for setting up and tuning Mason should read the Administrator's Manual (HTML::Mason::Admin). This document covers more advanced configuration scenarios and performance optimization. Reference companions to the Administrator's Manual include HTML::Mason::Parser, HTML::Mason::Interp, and HTML::Mason::ApacheHandler.
Most of this documentation assumes that you're running Mason on top of
mod_perl, since that is the most common configuration. If you are using
Mason outside of mod_perl, the documentation is still valid; you'll just
have to ignore mod_perl specific references like $r and the
ApacheHandler object, and you'll want to read the STANDALONE MODE section
in
HTML::Mason::Interp.