HTML::Mason::Request(3User Contributed Perl DocumentatiHTML::Mason::Request(3)NAMEHTML::Mason::Request - Mason Request Class
VERSION
version 1.54
SYNOPSIS
$m->abort (...)
$m->comp (...)
etc.
DESCRIPTION
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 $m. Outside of a component, you can use the class method
"instance".
COMPONENT PATHS
The methods Request->comp, Request->comp_exists, and
Request->fetch_comp take a component path argument. Component paths
are like URL paths, and always use a forward slash (/) as the
separator, regardless of what your operating system uses.
· If the path is absolute (starting with a '/'), then the component
is found relative to the component root.
· If the path is relative (no leading '/'), then the component is
found relative to the current component directory.
· If the path matches both a subcomponent and file-based component,
the subcomponent takes precedence.
PARAMETERS TO THE new() CONSTRUCTOR
autoflush
True or false, default is false. Indicates whether to flush the
output buffer ("$m->flush_buffer") after every string is output.
Turn on autoflush if you need to send partial output to the client,
for example in a progress meter.
As of Mason 1.3, autoflush will only work if enable_autoflush has
been set. Components can be compiled more efficiently if they
don't have to check for autoflush. Before using autoflush you might
consider whether a few manual "$m->flush_buffer" calls would work
nearly as well.
data_cache_api
The "$m->cache" API to use:
· '1.1', the default, indicates a "Cache::Cache" based API.
· 'chi' indicates a "CHI" based API.
· '1.0' indicates the custom cache API used in Mason 1.0x and
earlier. This compatibility layer is provided as a convenience
for users upgrading from older versions of Mason, but will not
be supported indefinitely.
data_cache_defaults
A hash reference of default options to use for the "$m->cache"
command. For example, to use Cache::Cache's "MemoryCache"
implementation by default:
data_cache_defaults => {cache_class => 'MemoryCache'}
To use the CHI "FastMmap" driver by default:
data_cache_api => 'CHI',
data_cache_defaults => {driver => 'FastMmap'},
These settings are overridden by options given to particular
"$m->cache" calls.
dhandler_name
File name used for dhandlers. Default is "dhandler". If this is
set to an empty string ("") then dhandlers are turned off entirely.
error_format
Indicates how errors are formatted. The built-in choices are
· brief - just the error message with no trace information
· text - a multi-line text format
· line - a single-line text format, with different pieces of
information separated by tabs (useful for log files)
· html - a fancy html format
The default format under Apache and CGI is either line or html
depending on whether the error mode is fatal or output,
respectively. The default for standalone mode is text.
The formats correspond to "HTML::Mason::Exception" methods named
as_format. You can define your own format by creating an
appropriately named method; for example, to define an "xml" format,
create a method "HTML::Mason::Exception::as_xml" patterned after
one of the built-in methods.
error_mode
Indicates how errors are returned to the caller. The choices are
fatal, meaning die with the error, and output, meaning output the
error just like regular output.
The default under Apache and CGI is output, causing the error to be
displayed in the browser. The default for standalone mode is
fatal.
component_error_handler
A code reference used to handle errors thrown during component
compilation or runtime. By default, this is a subroutine that turns
non-exception object errors in components into exceptions. If this
parameter is set to a false value, these errors are simply rethrown
as-is.
Turning exceptions into objects can be expensive, since this will
cause the generation of a stack trace for each error. If you are
using strings or unblessed references as exceptions in your code,
you may want to turn this off as a performance boost.
max_recurse
The maximum recursion depth for the component stack, for the
request stack, and for the inheritance stack. An error is signalled
if the maximum is exceeded. Default is 32.
out_method
Indicates where to send output. If out_method is a reference to a
scalar, output is appended to the scalar. If out_method is a
reference to a subroutine, the subroutine is called with each
output string. For example, to send output to a file called
"mason.out":
my $fh = new IO::File ">mason.out";
...
out_method => sub { $fh->print($_[0]) }
By default, out_method prints to standard output. Under Apache,
standard output is redirected to "$r->print".
plugins
An array of plugins that will be called at various stages of
request processing. Please see HTML::Mason::Plugin for details.
ACCESSOR METHODS
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:
my $max_recurse_level = $m->max_recurse;
$m->autoflush(1);
OTHER METHODS
abort ([return value])
Ends the current request, finishing the page without returning
through components. The optional argument specifies the return
value from "Interp::exec"; in a web environment, this ultimately
becomes the HTTP status code.
"abort" is implemented by throwing an HTML::Mason::Exception::Abort
object and can thus be caught by eval(). The "aborted" method is a
shortcut for determining whether a caught error was generated by
"abort".
If "abort" is called from a component that has a "<%filter>", than
any output generated up to that point is filtered, unless "abort"
is called from a "<%shared>" block.
clear_and_abort ([return value])
This method is syntactic sugar for calling "clear_buffer()" and
then "abort()". If you are aborting the request because of an
error, you will often want to clear the buffer first so that any
output generated up to that point is not sent to the client.
aborted ([$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
$@ to a temporary variable.
base_comp
Returns the current base component.
Here are the rules that determine base_comp as you move from
component to component.
· At the beginning of a request, the base component is
initialized to the requested component ("$m->request_comp()").
· When you call a regular component via a path, the base
component changes to the called component.
· When you call a component method via a path (/foo/bar:baz), the
base component changes to the method's owner.
· The base component does not change when:
· a component call is made to a component object
· a component call is made to SELF:x or PARENT:x or REQUEST:x
· a component call is made to a subcomponent (<%def>)
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, cache_options may include any valid options to the
new() method of the cache class. e.g. for "FileCache", valid
options include "default_expires_in" and "cache_depth".
See HTML::Mason::Cache::BaseCache for information about the
object returend 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 $output);
return;
}
...
Here is a piece of code that traps all errors occuring anywhere in
a component or its children, e.g. for the purpose of handling
application-specific exceptions. This is difficult to do with a
manual "eval" because it would have to span multiple code sections
and the main component body.
<%init>
my ($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).
APACHE-ONLY METHODS
These additional methods are available when running Mason with mod_perl
and the ApacheHandler.
ah Returns the ApacheHandler object associated with this request.
apache_req
Returns the Apache request object. This is also available in the
global $r.
auto_send_headers
True or false, default is true. Indicates whether Mason should
automatically send HTTP headers before sending content back to the
client. If you set to false, you should call "$r->send_http_header"
manually.
See the sending HTTP headers section of the developer's manual for
more details about the automatic header feature.
NOTE: This parameter has no effect under mod_perl-2, since calling
"$r->send_http_header" is no longer needed.
CGI-ONLY METHODS
This additional method is available when running Mason with the
CGIHandler module.
cgi_request
Returns the Apache request emulation object, which is available as
$r inside components.
See the CGIHandler docs for more details.
APACHE- OR CGI-ONLY METHODS
This method is available when Mason is running under either the
ApacheHandler or CGIHandler modules.
cgi_object
Returns the CGI object used to parse any CGI parameters submitted
to the component, assuming that you have not changed the default
value of the ApacheHandler args_method parameter. If you are using
the 'mod_perl' args method, then calling this method is a fatal
error. See the ApacheHandler and CGIHandler documentation for more
details.
redirect ($url, [$status])
Given a url, this generates a proper HTTP redirect for that URL. It
uses "$m->clear_and_abort" to clear out any previous output, and
abort the request. By default, the status code used is 302, but
this can be overridden by the user.
Since this is implemented using "$m->abort", it will be trapped by
an " eval {} " block. If you are using an " eval {} " block in
your code to trap errors, you need to make sure to rethrow these
exceptions, like this:
eval {
...
};
die $@ if $m->aborted;
# handle other exceptions
SEE ALSO
Mason
AUTHORS
· Jonathan Swartz <swartz@pobox.com>
· Dave Rolsky <autarch@urth.org>
· Ken Williams <ken@mathforum.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2012 by Jonathan Swartz.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
perl v5.18.2 2014-01-19 HTML::Mason::Request(3)
