Embperl - building dynamic websites with Perl

[ << Prev: SYNOPSIS ] [ Content ] [ Next: Runtime configuration >> ]

Embperl::Object allows you to build object-oriented (OO) websites using HTML components which implement inheritance via subdirectories. This enables elegant architectures and encourages code reuse. The use of inheritance also enables a website-wide "look and feel" to be specified in a single HTML file, which is then used as a template for every other page on the site. This template can include other modules which can be overridden in subdirectories; even the template itself can be overridden. In a nutshell, Embperl::Object makes the design of large websites much more intuitive, allowing object-oriented concepts to be utilised to the fullest while staying within the "rapid application development" model of Perl and HTML.

Embperl::Object is basically a mod_perl handler or could be invoked offline and helps you to build a whole page out of smaller parts. Basically it does the following:

When a request comes in, a page, which name is specified by EMBPERL_OBJECT_BASE, is searched in the same directory as the requested page. If the pages isn't found, Embperl::Object walking up the directory tree until it finds the page, or it reaches DocumentRoot or the directory specified by EMBPERL_OBJECT_STOPDIR.

This page is then called as frame for building the real page. Addtionaly Embperl::Object sets the search path to contain all directories it had to walk before finding that page. If EMBPERL_OBJECT_STOPDIR is set the path contains all directories up to the in EMBPERL_OBJECT_STOPDIR specified one.

This frame page can now include other pages, using the Embperl::Execute method. Because the search path is set by Embperl::Object the included files are searched in the directories starting at the directory of the original request walking up thru the directory which contains the base page. This means that you can have common files, like header, footer etc. in the base directory and override them as necessary in the subdirectory.

To include the original requested file, you need to call Execute with a '*' as filename. To call the the same file, but in an upper directory you can use the special shortcut ../*.

Additionally Embperl::Object sets up a inherence hierachie for you: The requested page inherit from the base page and the base page inherit from a class which could be specified by EMBPERL_OBJECT_HANDLER_CLASS, or if EMBPERL_OBJECT_HANDLER_CLASS is not set, from Embperl::Req. That allows you to define methods in base page and overwrite them as necessary in the original requested files. For this purpose a request object, which is blessed into the package of the requested page, is given as first parameter to each page (in $_[0]). Because this request object is a hashref, you can also use it to store additional data, which should be available in all components. Embperl does not use this hash itself, so you are free to store whatever you want. Methods can be ordinary Perl sub's (defined with [! sub foo { ... } !] ) or Embperl sub's (defined with [$sub foo $] .... [$endsub $]) .

[ << Prev: SYNOPSIS ] [ Content ] [ Next: Runtime configuration >> ]

© 1997-2023 Gerald Richter / actevy