NAME

Plasp::GlobalASA - global.asa

SYNOPSIS

  ### in global.asa
  sub Script_OnStart {
    printf STDERR "Executing script: %s\n", $Request->ServerVariables('SCRIPT_NAME');
  }

DESCRIPTION

The ASP platform allows developers to create Web Applications. In fulfillment of real software requirements, ASP allows event-triggered actions to be taken, which are defined in a global.asa file. The global.asa file resides in the Global directory, defined as a config option, and may define the following actions:

  Action              Event
  ------              ------
  Script_OnStart *    - Beginning of Script execution
  Script_OnEnd *      - End of Script execution
  Script_OnFlush *    - Before $Response being flushed to client.
  Script_OnParse *    - Before script compilation
  Application_OnStart - Beginning of Application
  Application_OnEnd   - End of Application
  Session_OnStart     - Beginning of user Session.
  Session_OnEnd       - End of user Session.

  * These are API extensions that are not portable, but were
    added because they are incredibly useful

These actions must be defined in the "$self->Global/global.asa" file as subroutines, for example:

  sub Session_OnStart {
    $Application->{$Session->SessionID()} = started;
  }

Sessions are easy to understand. When visiting a page in a web application, each user has one unique $Session. This session expires, after which the user will have a new $Session upon revisiting.

A web application starts when the user visits a page in that application, and has a new $Session created. Right before the first $Session is created, the $Application is created. When the last user $Session expires, that $Application expires also. For some web applications that are always busy, the Application_OnEnd event may never occur.

METHODS

$self->execute_event($event);

Execute the event defined in global.asa

Application_OnStart

This event marks the beginning of an ASP application, and is run just before the Session_OnStart of the first Session of an application. This event is useful to load up $Application with data that will be used in all user sessions.

Application_OnEnd

The end of the application is marked by this event, which is run after the last user session has timed out for a given ASP application.

Session_OnStart

Triggered by the beginning of a user's session, Session_OnStart gets run before the user's executing script, and if the same session recently timed out, after the session's triggered Session_OnEnd.

The Session_OnStart is particularly useful for caching database data, and avoids having the caching handled by clumsy code inserted into each script being executed.

Session_OnEnd

Triggered by a user session ending, Session_OnEnd can be useful for cleaning up and analyzing user data accumulated during a session.

Sessions end when the session timeout expires, and the StateManager performs session cleanup. The timing of the Session_OnEnd does not occur immediately after the session times out, but when the first script runs after the session expires, and the StateManager allows for that session to be cleaned up.

So on a busy site with default SessionTimeout (20 minutes) and StateManager (10 times) settings, the Session_OnEnd for a particular session should be run near 22 minutes past the last activity that Session saw. A site infrequently visited will only have the Session_OnEnd run when a subsequent visit occurs, and theoretically the last session of an application ever run will never have its Session_OnEnd run.

Thus I would not put anything mission-critical in the Session_OnEnd, just stuff that would be nice to run whenever it gets run.

Script_OnStart

The script events are used to run any code for all scripts in an application defined by a global.asa. Often, you would like to run the same code for every script, which you would otherwise have to add by hand, or add with a file include, but with these events, just add your code to the global.asa, and it will be run. This runs before a script is executed.

Script_OnEnd

Like Script_OnStart except at the end.

There is one caveat. Code in Script_OnEnd is not guaranteed to be run when $Response->End() is called, since the program execution ends immediately at this event. To always run critical code, use the API extension:

  $Server->RegisterCleanup()

Script_OnParse

This event allows one to set up a source filter on the script text, allowing one to change the script on the fly before the compilation stage occurs. The script text is available in the $Server->{ScriptRef} scalar reference, and can be accessed like so:

 sub Script_OnParse {
   my $code = $Server->{ScriptRef}
   $$code .= " ADDED SOMETHING ";
 }

Script_OnFlush

API extension. This event will be called prior to flushing the $Response buffer to the web client. At this time, the $Response->{BinaryRef} buffer reference may be used to modify the buffered output at runtime to apply global changes to scripts output without having to modify all the scripts.

  sub Script_OnFlush {
    my $ref = $Response->{BinaryRef};
    $$ref =~ s/\s+/ /sg; # to strip extra white space
  }

SEE ALSO

• Plasp