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HTML::Mason::Request(3) |
User Contributed Perl Documentation |
HTML::Mason::Request(3) |
HTML::Mason::Request - Mason Request Class
$m->abort (...)
$m->comp (...)
etc.
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 $m. Outside of
a component, you can use the class method "instance".
The methods Request->comp, Request->comp_exists, and
Request->fetch_comp take a component path argument. Component paths are
like URL paths, and always use a forward slash (/) as the separator,
regardless of what your operating system uses.
- •
- If the path is absolute (starting with a '/'), then the component is found
relative to the component root.
- •
- If the path is relative (no leading '/'), then the component is found
relative to the current component directory.
- •
- If the path matches both a subcomponent and file-based component, the
subcomponent takes precedence.
- autoflush
- True or false, default is false. Indicates whether to flush the output
buffer ("$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.
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;
$m->autoflush(1);
- abort ([return value])
- Ends the current request, finishing the page without returning through
components. The optional argument specifies the return value from
"Interp::exec"; in a web environment, this ultimately becomes
the HTTP status code.
"abort" is implemented by throwing an
HTML::Mason::Exception::Abort object and can thus be caught by
eval(). The "aborted" method is a shortcut for
determining whether a caught error was generated by "abort".
If "abort" is called from a component that has a
"<%filter>", than any output generated up to that point is
filtered, unless "abort" is called from a
"<%shared>" block.
- clear_and_abort ([return value])
- This method is syntactic sugar for calling "clear_buffer()" and
then "abort()". If you are aborting the request because of an
error, you will often want to clear the buffer first so that any output
generated up to that point is not sent to the client.
- aborted ([$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 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.
- 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.
This additional method is available when running Mason with the CGIHandler
module.
- cgi_request
- Returns the Apache request emulation object, which is available as $r
inside components.
See the CGIHandler docs for more details.
This method is available when Mason is running under either the ApacheHandler or
CGIHandler modules.
- cgi_object
- Returns the CGI object used to parse any CGI parameters submitted to the
component, assuming that you have not changed the default value of the
ApacheHandler args_method parameter. If you are using the 'mod_perl' args
method, then calling this method is a fatal error. See the ApacheHandler
and CGIHandler documentation for more details.
- redirect ($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
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