The Request API is your gateway to all Mason features not provided by
syntactic tags. Mason creates a new Request object for every web
request. Inside a component you access the current request object via
the global $m. Outside of a component, you can use the class
method instance.
All of the above properties have standard accessor methods of the same
name. In general, no arguments retrieves the value, and one argument
sets and returns the value. For example:
- abort ([return value])
-
Ends the current request, finishing the page without returning
through components. The optional argument specifies the return
value from Interp::exec; in a web environment, this ultimately
becomes the HTTP status code.
abort is implemented by throwing an HTML::Mason::Exception::Abort
object and can thus be caught by eval(). The aborted method is a
shortcut for determining whether a caught error was generated by
abort.
If abort is called from a component that has a <%filter>,
than any output generated up to that point is filtered, unless
abort is called from a <%shared> block.
- clear_and_abort ([return value])
-
This method is syntactic sugar for calling clear_buffer() and then
abort(). If you are aborting the request because of an error, you
will often want to clear the buffer first so that any output generated
up to that point is not sent to the client.
- aborted ([$err])
-
Returns true or undef indicating whether the specified $err
was generated by abort. If no $err was passed, uses $@.
In this code, we catch and process fatal errors while letting abort
exceptions pass through:
eval { code_that_may_fail_or_abort() };
if ($@) {
die $@ if $m->aborted;
# handle fatal errors...
$@ can lose its value quickly, so if you are planning to call
$m->aborted more than a few lines after the eval, you should save $@
to a temporary variable.
- base_comp
-
Returns the current base component.
Here are the rules that determine base_comp as you move from
component to component.
This may return nothing if the base component is not yet known, for
example inside a plugin's start_request_hook() method, where we
have created a request but it does not yet know anything about the
component being called.
- cache
-
$m->cache returns a new cache object with a
namespace specific to this component. The parameters to and return value from
$m->cache differ depending on which data_cache_api you are using.
- If data_cache_api = 1.1 (default)
-
cache_class specifies the class of cache object to create. It
defaults to
FileCache in most cases, or MemoryCache if the
interpreter has no data directory, and must be a backend subclass of
Cache::Cache. The prefix ``Cache::'' need not be included. See the
Cache::Cache package for a full list of backend subclasses.
Beyond that, I<cache_options> may include any valid options to the new() method of the
cache class. e.g. for C<FileCache>, valid options include C<default_expires_in> and
C<cache_depth>.
See HTML::Mason::Cache::BaseCache for
information about the object returned from $m->cache.
- If data_cache_api = CHI
-
chi_root_class specifies the factory class that will be called to
create cache objects. The default is 'CHI'.
driver specifies the driver to use, for example Memory or
FastMmap. The default is File in most cases, or Memory if
the interpreter has no data directory.
Beyond that, cache_options may include any valid options to the
new() method of the driver. e.g. for the File driver, valid options
include expires_in and depth.
- cache_self ([expires_in => '...'], [key => '...'], [get_options], [cache_options])
-
$m->cache_self caches the entire output and return result of a
component.
cache_self either returns undef, or a list containing the
return value of the component followed by '1'. You should return
immediately upon getting the latter result, as this indicates
that you are inside the second invocation of the component.
cache_self takes any of parameters to $m->cache
(e.g. cache_depth), any of the optional parameters to
$cache->get (expire_if, busy_lock), and two additional
options:
-
expire_in or expires_in: Indicates when the cache expires - it
is passed as the third argument to
$cache->set. e.g. '10 sec',
'5 min', '2 hours'.
-
key: An identifier used to uniquely identify the cache results - it
is passed as the first argument to
$cache->get and
$cache->set. The default key is '__mason_cache_self__'.
To cache the component's output:
<%init>
return if $m->cache_self(expire_in => '10 sec'[, key => 'fookey']);
... <rest of init> ...
</%init>
To cache the component's scalar return value:
<%init>
my ($result, $cached) = $m->cache_self(expire_in => '5 min'[, key => 'fookey']);
return $result if $cached;
... <rest of init> ...
</%init>
To cache the component's list return value:
<%init>
my (@retval) = $m->cache_self(expire_in => '3 hours'[, key => 'fookey']);
return @retval if pop @retval;
... <rest of init> ...
</%init>
We call pop on @retval to remove the mandatory '1' at the end of
the list.
If a component has a <%filter> block, then the filtered
output is cached.
Note: users upgrading from 1.0x and earlier can continue to use the
old $m->cache_self API by setting data_cache_api to '1.0'.
This support will be removed at a later date.
See the the DATA CACHING section of the developer's manual section for more details on how to
exercise finer control over caching.
- caller_args
-
Returns the arguments passed by the component at the specified stack
level. Use a positive argument to count from the current component and
a negative argument to count from the component at the bottom of the
stack. e.g.
$m->caller_args(0) # arguments passed to current component
$m->caller_args(1) # arguments passed to component that called us
$m->caller_args(-1) # arguments passed to first component executed
When called in scalar context, a hash reference is returned. When
called in list context, a list of arguments (which may be assigned to
a hash) is returned. Returns undef or an empty list, depending on
context, if the specified stack level does not exist.
- callers
-
With no arguments, returns the current component stack as a list of
component objects, starting with the current component and ending with
the top-level component. With one numeric argument, returns the
component object at that index in the list. Use a positive argument to
count from the current component and a negative argument to count from
the component at the bottom of the stack. e.g.
my @comps = $m->callers # all components
$m->callers(0) # current component
$m->callers(1) # component that called us
$m->callers(-1) # first component executed
Returns undef or an empty list, depending on context, if the specified
stack level does not exist.
- caller
-
A synonym for $m->callers(1), i.e. the component that called the
currently executing component.
- call_next ([args...])
-
Calls the next component in the content wrapping chain; usually called
from an autohandler. With no arguments, the original arguments are
passed to the component. Any arguments specified here serve to
augment and override (in case of conflict) the original
arguments. Works like $m->comp in terms of return value and
scalar/list context. See the autohandlers section of the developer's manual for examples.
- call_self (output, return, error, tag)
-
This method allows a component to call itself so that it can filter
both its output and return values. It is fairly advanced; for most
purposes the
<%filter> tag will be sufficient and simpler.
$m->call_self takes four arguments, all of them optional.
- output - scalar reference that will be populated with the
component output.
-
- return - scalar reference that will be populated with the
component return value.
-
- error - scalar reference that will be populated with the error
thrown by the component, if any. If this parameter is not defined,
then call_self will not catch errors.
-
- tag - a name for this call_self invocation; can almost always be omitted.
-
$m->call_self acts like a fork() in the sense that it will
return twice with different values. When it returns 0, you allow
control to pass through to the rest of your component. When it
returns 1, that means the component has finished and you can
examine the output, return value and error. (Don't worry, it doesn't
really do a fork! See next section for explanation.)
The following examples would generally appear at the top of a <
<%init >> section. Here is a no-op $m->call_self that leaves
the output and return value untouched:
<%init>
my ($output, $retval);
if ($m->call_self(\$output, \$retval)) {
$m->print($output);
return $retval;
}
...
Here is a simple output filter that makes the output all uppercase.
Note that we ignore both the original and the final return value.
<%init>
my ($output, $error);
if ($m->call_self(\$output, undef)) {
$m->print(uc $output);
return;
}
...
Here is a piece of code that traps all errors occurring anywhere in a
component or its children, e.g. for the purpose of handling
application-specific exceptions. This is difficult to do with a manual
eval because it would have to span multiple code sections and the
main component body.
<%init>
my ($output, undef, $error);
if ($m->call_self(\$output, undef, \$error)) {
if ($error) {
# check $error and do something with it
}
$m->print($output);
return;
}
...
- clear_buffer
-
Clears the Mason output buffer. Any output sent before this line is
discarded. Useful for handling error conditions that can only be
detected in the middle of a request.
clear_buffer is, of course, thwarted by flush_buffer.
- comp (comp, args...)
-
Calls the component designated by comp with the specified
option/value pairs. comp may be a component path or a component
object.
Components work exactly like Perl subroutines in terms of return
values and context. A component can return any type of value, which is
then returned from the $m->comp call.
The <& &> tag provides a convenient shortcut for $m->comp.
As of 1.10, component calls can accept an initial hash reference of
modifiers. The only currently supported modifier is store, which
stores the component's output in a scalar reference. For example:
my $buf;
my $return = $m->comp( { store => \$buf }, '/some/comp', type => 'big' );
This mostly duplicates the behavior of scomp, but can be useful in
rare cases where you need to capture both a component's output and
return value.
This modifier can be used with the <& &> tag as well, for example:
<& { store => \$buf }, '/some/comp', size => 'medium' &>
- comp_exists (comp_path)
-
Returns 1 if comp_path is the path of an existing component, 0
otherwise. comp_path may be any path accepted by
comp or
fetch_comp, including method or
subcomponent paths.
Depending on implementation, <comp_exists> may try to load the
component referred to by the path, and may throw an error if the
component contains a syntax error.
- content
-
Evaluates the content (passed between <&| comp &> and </&> tags) of the
current component, and returns the resulting text.
Returns undef if there is no content.
- has_content
-
Returns true if the component was called with content (i.e. with <&|
comp &> and </&> tags instead of a single <& comp &> tag). This is
generally better than checking the defined'ness of $m->content
because it will not try to evaluate the content.
- count
-
Returns the number of this request, which is unique for a given
request and interpreter.
- current_args
-
Returns the arguments passed to the current component. When called in
scalar context, a hash reference is returned. When called in list
context, a list of arguments (which may be assigned to a hash) is
returned.
- current_comp
-
Returns the current component object.
- decline
-
Used from a top-level component or dhandler, this method clears the
output buffer, aborts the current request and restarts with the next
applicable dhandler up the tree. If no dhandler is available, a
not-found error occurs.
This method bears no relation to the Apache DECLINED status except in
name.
- declined ([$err])
-
Returns true or undef indicating whether the specified $err was
generated by decline. If no $err was passed, uses $@.
- depth
-
Returns the current size of the component stack. The lowest possible
value is 1, which indicates we are in the top-level component.
- dhandler_arg
-
If the request has been handled by a dhandler, this method returns the
remainder of the URI or Interp::exec path when the dhandler directory is
removed. Otherwise returns undef.
dhandler_arg may be called from any component in the request, not just
the dhandler.
- exec (comp, args...)
-
Starts the request by executing the top-level component and
arguments. This is normally called for you on the main request, but
you can use it to execute subrequests.
A request can only be executed once; e.g. it is an error to call this
recursively on the same request.
- fetch_comp (comp_path)
-
Given a comp_path, returns the corresponding component object or
undef if no such component exists.
- fetch_next
-
Returns the next component in the content wrapping chain, or undef if
there is no next component. Usually called from an autohandler. See
the autohandlers section of the developer's manual for usage and examples.
- fetch_next_all
-
Returns a list of the remaining components in the content wrapping
chain. Usually called from an autohandler. See the autohandlers section of the developer's manual
for usage and examples.
- file (filename)
-
Returns the contents of filename as a string. If filename is a
relative path, Mason prepends the current component directory.
- flush_buffer
-
Flushes the Mason output buffer. Under mod_perl, also sends HTTP
headers if they haven't been sent and calls $r->rflush to flush
the Apache buffer. Flushing the initial bytes of output can make your
servers appear more responsive.
Attempts to flush the buffers are ignored within the context of a call
to $m->scomp or when output is being stored in a scalar
reference, as with the { store => \$out } component call
modifier.
<%filter> blocks will process the output whenever the buffers
are flushed. If autoflush is on, your data may be filtered in
small pieces.
- instance
-
This class method returns the HTML::Mason::Request currently in
use. If called when no Mason request is active it will return
undef.
If called inside a subrequest, it returns the subrequest object.
- interp
-
Returns the Interp object associated with this request.
- make_subrequest (comp => path, args => arrayref, other parameters)
-
This method creates a new Request object which inherits its parent's
settable properties, such as autoflush and out_method. These
values may be overridden by passing parameters to this method.
The comp parameter is required, while all other parameters are
optional. It may be specified as an absolute path or as a path
relative to the current component.
See the subrequests section of the developer's manual for more information about subrequests.
- log
-
Returns a Log::Any logger with a log category specific to the
current component. The category for a component ``/foo/bar'' would be
``HTML::Mason::Component::foo::bar''.
- notes (key, value)
-
The notes() method provides a place to store application data,
giving developers a way to share data among multiple components. Any
data stored here persists for the duration of the request, i.e. the
same lifetime as the Request object.
Conceptually, notes() contains a hash of key-value pairs.
notes($key, $value) stores a new entry in this hash.
notes($key) returns a previously stored value. notes() without
any arguments returns a reference to the entire hash of key-value
pairs.
notes() is similar to the mod_perl method $r->pnotes(). The
main differences are that this notes() can be used in a
non-mod_perl environment, and that its lifetime is tied to the
Mason request object, not the Apache request object. In
particular, a Mason subrequest has its own notes() structure, but
would access the same $r->pnotes() structure.
- out (string)
-
A synonym for $m->print.
- print (string)
-
Print the given string. Rarely needed, since normally all text is just
placed in the component body and output implicitly. $m->print is useful
if you need to output something in the middle of a Perl block.
In 1.1 and on, print and $r->print are remapped to $m->print,
so they may be used interchangeably. Before 1.1, one should only use
$m->print.
- request_args
-
Returns the arguments originally passed to the top level component
(see request_comp for
definition). When called in scalar context, a hash reference is
returned. When called in list context, a list of arguments (which may
be assigned to a hash) is returned.
- request_comp
-
Returns the component originally called in the request. Without
autohandlers, this is the same as the first component executed. With
autohandlers, this is the component at the end of the
$m->call_next chain.
- request_depth
-
Returns the current size of the request/subrequest stack. The lowest
possible value is 1, which indicates we are in the top-level request.
A value of 2 indicates we are inside a subrequest of the top-level request,
and so on.
- scomp (comp, args...)
-
Like comp, but returns the component output as a string
instead of printing it. (Think sprintf versus printf.) The
component's return value is discarded.
- subexec (comp, args...)
-
This method creates a new subrequest with the specified top-level
component and arguments, and executes it. This is most often used
to perform an ``internal redirect'' to a new component such that
autohandlers and dhandlers take effect.
- time
-
Returns the interpreter's notion of the current time (deprecated).
These additional methods are available when running Mason with mod_perl
and the ApacheHandler.
This additional method is available when running Mason with the
CGIHandler module.
This method is available when Mason is running under either the
ApacheHandler or CGIHandler modules.