HTML::Mason::Plugin(3pm)				User Contributed Perl Documentation				  HTML::Mason::Plugin(3pm)

NAME

       HTML::Mason::Plugin - Plugin Base class for Mason

SYNOPIS

	  package MasonX::Plugin::Timer;
	  use base qw(HTML::Mason::Plugin);
	  use Time::HiRes;

	  sub start_component_hook {
	      my ($self, $context) = @_;
	      push @{$self->{ timers }}, Time::HiRes::time;
	  }

	  sub end_component_hook {
	      my ($self, $context) = @_;
	      my $elapsed = Time::HiRes::time - pop @{$self->{ timers }};
	      printf STDERR "Component '%s' took %.1f seconds
",
		  $context->comp->title, $elapsed;
	  }

	  1;

DESCRIPTION

       Use a Mason plugin to have actions occur at the beginning or end of requests or components. Plugins are activated by passing plugins in the
       interpreter or request object. Each plugin in the list can be specified as a class name (in which case the plugin object is created once
       for each request) or as an actual object of the plugin class.

       If your plugin can be configured, place the configuration in class variables - for example,

	   $MasonX::Plugin::Timer::Units = 'seconds';

       These can be set either from httpd.conf via PerlSetVar directives, or in perl directly from a handler.pl file.

PLUGIN HOOKS

       A plugin class defines one or more of the following hooks (methods): start_request_hook, end_request_hook, start_component_hook, and
       end_component_hook.

       Every hook receives two arguments: the plugin object itself, and a context object with various methods.

       start_request_hook
	   "start_request_hook" is called before the Mason request begins execution.  Its context has the following read-only methods:

	       request # the current request ($m)
	       args    # arguments the request was called with

	   When called in scalar context, args returns a list reference which may be modified to change or add to the arguments passed to the
	   first component. When called in list context, args returns a list (which may be assigned to a hash).

	   Note that subrequests (see HTML::Mason::Request will create a new plugin object and execute this code again; you can skip your code for
	   subrequests by checking "is_subrequest" on request. e.g.

	      sub start_request_hook {
		  my ($self, $context) = @_;
		  unless ($context->request->is_subrequest()) {
		      # perform hook action
		  }
	      }

	   Currently, this hook is called before any information about the requested component is available, so you cannot call methods like
	   "base_comp()" or "request_args()" on the Request object.

       end_request_hook
	   "end_request_hook" is called before the Mason request exits. Its context has the following read-only methods:

	       request	   # the current request ($m)
	       args	   # arguments the request was called with
	       output	   # reference to the contents of the output buffer
	       wantarray   # value of wantarray the request was called with
	       result	   # arrayref of value(s) that the request is about to return
	       error	   # reference to error, if any, that the request is about to throw

	   When called in scalar context, args returns a list reference; when called in list context, it returns a list (which may be assigned to
	   a hash).

	   result always contains an array ref; if wantarray is 0, the return value is the the first element of that array. The plugin may modify
	   output to affect what the request outputs, and result and error to affect what the request returns.

       start_component_hook
	   "start_component_hook" is called before a component begins executing. Its context has the following read-only methods:

	       request	   # the current request ($m)
	       comp	   # the component object
	       args	   # arrayref of arguments the component was called with

	   The plugin may NOT modify args currently.

       end_component_hook
	   "end_component_hook()" is called after a component has completed. Its context has the following read-only methods:

	       request	   # the current request ($m)
	       comp	   # the component object
	       args	   # arrayref of arguments the component was called with
	       wantarray   # value of wantarray the component was called with
	       result	   # arrayref of value(s) that the component is about to return
	       error	   # reference to error, if any, that the component is about to throw

	   result always contains an array ref; if wantarray is 0, the return value is the first element of that array.  The plugin may modify
	   both result and error to affect how the request returns.

	   It would be desirable for this hook to have access to the component's output as well as its return value, but this is currently
	   impossible because output from multiple components combine into a single buffer.

WARNINGS

       Do not keep an unweakened reference to a request or component object in your plugin object, or you will create a nasty circular reference.

AUTHORS

       Doug Treder, Jonathan Swartz, Dave Rolsky

SEE ALSO

       HTML::Mason::Interp, HTML::Mason::Request

perl v5.14.2							    2012-02-04						  HTML::Mason::Plugin(3pm)