man HTML::Mason::Interp (3): Mason Component Interpreter

SYNOPSIS

my $i = HTML::Mason::Interp->new (data_dir=>'/usr/local/mason',
comp_root=>'/usr/local/www/htdocs/',
...other params...);

DESCRIPTION

Interp is the Mason workhorse, executing components and routing their output and errors to all the right places. In a mod_perl environment, Interp objects are handed off immediately to an ApacheHandler object which internally calls the Interp implementation methods. In that case the only user method is the new() constructor.

PARAMETERS TO THE new() CONSTRUCTOR

autohandler_name

File name used for autohandlers. Default is ``autohandler''. If this is set to an empty string ("") then autohandlers are turned off entirely.

buffer_preallocate_size

Number of bytes to preallocate in the output buffer for each request. Defaults to 0. Setting this to, say, your maximum page size (or close to it) can reduce the number of reallocations Perl performs as components add to the output buffer.

code_cache_max_size

Specifies the maximum number of components that should be held in the in-memory code cache. The default is 'unlimited', meaning no components will ever be discarded; Mason can perform certain optimizations in this mode. Setting this to zero disables the code cache entirely. See the code cache section of the administrator's manual for further details.

comp_root

The component root marks the top of your component hierarchy and defines how component paths are translated into real file paths. For example, if your component root is /usr/local/httpd/docs, a component path of /products/index.html translates to the file /usr/local/httpd/docs/products/index.html.

Under Apache and CGI, comp_root defaults to the server's document root. In standalone mode comp_root defaults to the current working directory.

This parameter may be either a scalar or an array reference. If it is a scalar, it should be a filesystem path indicating the component root. If it is an array reference, it should be of the following form:

 [ [ foo => '/usr/local/foo' ],
   [ bar => '/usr/local/bar' ] ]

This is an array of two-element array references, not a hash. The ``keys'' for each path must be unique and their ``values'' must be filesystem paths. These paths will be searched in the provided order whenever a component path is resolved. For example, given the above component roots and a component path of /products/index.html, Mason would search first for /usr/local/foo/products/index.html, then for /usr/local/bar/products/index.html.

The keys are used in several ways. They help to distinguish component caches and object files between different component roots, and they appear in the "title()" of a component.

When you specify a single path for a component root, this is actually translated into

  [ [ MAIN => path ] ]

If you have turned on dynamic_comp_root, you may modify the component root(s) of an interpreter between requests by calling "$interp->comp_root" with a value. However, the path associated with any given key may not change between requests. For example, if the initial component root is

 [ [ foo => '/usr/local/foo' ],
   [ bar => '/usr/local/bar' ], ]

then it may not be changed to

 [ [ foo => '/usr/local/bar' ],
   [ bar => '/usr/local/baz' ],

but it may be changed to

 [ [ foo   => '/usr/local/foo' ],
   [ blarg => '/usr/local/blarg' ] ]

In other words, you may add or remove key/path pairs but not modify an already-used key/path pair. The reason for this restriction is that the interpreter maintains a component cache per key that would become invalid if the associated paths were to change.

compiler

The Compiler object to associate with this Interpreter. By default a new object of class compiler_class will be created.

compiler_class

The class to use when creating a compiler. Defaults to HTML::Mason::Compiler.

data_dir

The data directory is a writable directory that Mason uses for various features and optimizations: for example, component object files and data cache files. Mason will create the directory on startup, if necessary, and set its permissions according to the web server User/Group.

Under Apache, data_dir defaults to a directory called ``mason'' under the Apache server root. You will need to change this on certain systems that assign a high-level server root such as /usr!

In non-Apache environments, data_dir has no default. If it is left unspecified, Mason will not use object files, and the default data cache class will be "MemoryCache" instead of "FileCache".

dynamic_comp_root

True or false, defaults to false. Indicates whether the comp_root can be modified on this interpreter between requests. Mason can perform a few optimizations with a fixed component root, so you should only set this to true if you actually need it.

escape_flags

A hash reference of escape flags to set for this object. See the section on the set_escape method for more details.

ignore_warnings_expr

Regular expression indicating which warnings to ignore when loading components. Any warning that is not ignored will prevent the component from being loaded and executed. For example:

    ignore_warnings_expr =>
        'Global symbol.*requires explicit package'

If set to undef, all warnings are heeded. If set to '.', warnings are turned off completely as a specially optimized case.

By default, this is set to 'Subroutine .* redefined'. This allows you to declare global subroutines inside <%once> sections and not receive an error when the component is reloaded.

object_file_extension

Extension to add to the end of object files. Default is ``.obj''.

preloads

A list of component paths, optionally with glob wildcards, to load when the interpreter initializes. e.g.

    preloads => ['/foo/index.html','/bar/*.pl']

Default is the empty list. For maximum performance, this should only be used for components that are frequently viewed and rarely updated. See the preloading components section of the administrator's manual for further details.

As mentioned in the developer's manual, a component's "<%once>" section is executed when it is loaded. For preloaded components, this means that this section will be executed before a Mason or Apache request exist, so preloading a component that uses $m or $r in a "<%once>" section will fail.

request_class

The class to use when creating requests. Defaults to HTML::Mason::Request.

resolver

The Resolver object to associate with this Compiler. By default a new object of class resolver_class will be created.

resolver_class

The class to use when creating a resolver. Defaults to HTML::Mason::Resolver::File.

static_source

True or false, default is false. When false, Mason checks the timestamp of the component source file each time the component is used to see if it has changed. This provides the instant feedback for source changes that is expected for development. However it does entail a file stat for each component executed.

When true, Mason assumes that the component source tree is unchanging: it will not check component source files to determine if the memory cache or object file has expired. This can save many file stats per request. However, in order to get Mason to recognize a component source change, you must flush the memory cache and remove object files. See static_source_touch_file for one easy way to arrange this.

We recommend turning this mode on in your production sites if possible, if performance is of any concern.

static_source_touch_file

Specifies a filename that Mason will check once at the beginning of of every request. When the file timestamp changes, Mason will (1) clear its in-memory component cache, and (2) remove object files if they have not already been deleted by another process.

This provides a convenient way to implement static_source mode. All you need to do is make sure that a single file gets touched whenever components change. For Mason's part, checking a single file at the beginning of a request is much cheaper than checking every component file when static_source=0.

use_object_files

True or false, default is true. Specifies whether Mason creates object files to save the results of component parsing. You may want to turn off object files for disk space reasons, but otherwise this should be left alone.

ACCESSOR METHODS

All of the above properties have standard accessor methods of the same name. Only comp_root and ignore_warnings_expr can be modified in an existing interpreter; the rest are read-only.

ESCAPE FLAG METHODS

apply_escapes ($text, $flags, [more flags...])

This method applies a one or more escapes to a piece of text. The escapes are specified by giving their flag. Each escape is applied to the text in turn, after which the now-modified text is returned.

remove_escape ($name)

Given an escape name, this removes that escape from the interpreter's known escapes. If the name is not recognized, it is simply ignored.

set_escape ($name => see below])

This method is called to add an escape flag to the list of known escapes for the interpreter. The flag may only consist of the characters matching "\w" and the dash (-). It must start with an alpha character or an underscore (_).

The right hand side may be one of several things. It can be a subroutine reference. It can also be a string match "/^\w+$/", in which case it is assumed to be the name of a subroutine in the "HTML::Mason::Escapes" module. Finally, if it is a string that does not match the above regex, then it is assumed to be "eval"able code, which will return a subroutine reference.

When setting these with "PerlSetVar" directives in an Apache configuration file, you can set them like this:

  PerlSetVar  MasonEscapeFlags  "h => \&HTML::Mason::Escapes::basic_html_escape"
  PerlSetVar  MasonEscapeFlags  "flag  => \&subroutine"
  PerlSetVar  MasonEscapeFlags  "uc    => sub { ${$_[0]} = uc ${$_[0]}; }"
  PerlAddVar  MasonEscapeFlags  "thing => other_thing"

OTHER METHODS

comp_exists (path)

Given an absolute component path, this method returns a boolean value indicating whether or not a component exists for that path.

exec (comp, args...)

Creates a new HTML::Mason::Request object for the given comp and args, and executes it. The return value is the return value of comp, if any.

This is useful for running Mason outside of a web environment. See ``using Mason from a standalone script'' in HTML::Mason::Admin for examples.

This method isn't generally useful in a mod_perl environment; see subrequests instead.

flush_code_cache

Empties the component cache. When using Perl 5.00503 or earlier, you should call this when finished with an interpreter, in order to remove circular references that would prevent the interpreter from being destroyed.

load (path)

Returns the component object corresponding to an absolute component "path", or undef if none exists. Dies with an error if the component fails to load because of a syntax error.

make_component (comp_source => ... )

make_component (comp_file => ... )

This method compiles Mason component source code and returns a Component object. The source may be passed in as a string in "comp_source", or as a filename in "comp_file". When using "comp_file", the filename is specified as a path on the file system, not as a path relative to Mason's component root (see $m->fetch_comp for that).

If Mason encounters an error during processing, an exception will be thrown.

Example of usage:

    # Make an anonymous component
    my $anon_comp =
      eval { $interp->make_component
               ( comp_source => '<%perl>my $name = "World";</%perl>Hello <% $name %>!' ) };
    die $@ if $@;
    $m->comp($anon_comp);

make_request (@request_params)

This method creates a Mason request object. The arguments to be passed are the same as those for the "HTML::Mason::Request->new" constructor or its relevant subclass. This method will likely only be of interest to those attempting to write new handlers or to subclass "HTML::Mason::Interp". If you want to create a subrequest, see subrequests instead.

purge_code_cache ()

Called during request execution in order to clear out the code cache. Mainly useful to subclasses that may want to take some custom action upon clearing the cache.

set_global ($varname, [values...])

This method sets a global to be used in components. "varname" is a variable name, optionally preceded with a prefix ("$", "@", or "%"); if the prefix is omitted then "$" is assumed. "varname" is followed by a value, in the case of a scalar, or by one or more values in the case of a list or hash. For example:

    # Set a global variable $dbh containing the database handle
    $interp->set_global(dbh => DBI->connect(...));
    # Set a global hash %session from a local hash
    $interp->set_global('%session', %s);

The global is set in the package that components run in: usually "HTML::Mason::Commands", although this can be overridden via the in_package parameter. The lines above, for example, are equivalent to:

    $HTML::Mason::Commands::dbh = DBI->connect(...);
    %HTML::Mason::Commands::session = %s;

assuming that in_package has not been changed.