NAME¶
Dancer::Exception - class for throwing and catching exceptions
VERSION¶
version 1.3132
SYNOPSIS¶
use Dancer::Exception qw(:all);
register_exception('DataProblem',
message_pattern => "test message : %s"
);
sub do_stuff {
raise DataProblem => "we've lost data!";
}
try {
do_stuff()
} catch {
# an exception was thrown
my ($exception) = @_;
if ($exception->does('DataProblem')) {
# handle the data problem
my $message = $exception->message();
} else {
$exception->rethrow
}
};
DESCRIPTION¶
Dancer::Exception is based on Try::Tiny. You can try and catch exceptions, like
in Try::Tiny.
Exceptions are objects, from subclasses of Dancer::Exception::Base.
However, for internal Dancer usage, we introduce a special class of exceptions,
called Dancer::Continuation. Exceptions that are from this class are not
caught with a "catch" block, but only with a
"continuation". That's a cheap way to implement a
workflow
interruption. Dancer users should ignore this feature.
What it means for Dancer users¶
Users can throw and catch exceptions, using "try" and
"catch". They can reuse some Dancer core exceptions
("Dancer::Exception::Base::*"), but they can also create new
exception classes, and use them for their own means. That way it's easy to use
custom exceptions in a Dancer application. Have a look at
"register_exception", "raise", and the methods in
Dancer::Exception::Base.
METHODS¶
try¶
Same as in Try::Tiny
catch¶
Same as in Try::Tiny. The exception can be retrieved as the first parameter:
try { ... } catch { my ($exception) = @_; };
continuation¶
To be used by Dancer developers only, in Dancer core code.
raise¶
# raise Dancer::Exception::Base::Custom
raise Custom => "user $username is unknown";
# raise Dancer::Exception::Base::Custom::Frontend
raise 'Custom::Frontend' => "user $username is unknown";
# same, raise Dancer::Exception::Base::Custom::Frontend
raise custom_frontend => "user $username is unknown";
# raise My::Own::ExceptionSystem::Invalid::Login
raise '+My::Own::ExceptionSystem::Invalid::Login' => "user $username is unknown";
raise provides an easy way to throw an exception. First parameter is the name of
the exception class, without the "Dancer::Exception::" prefix. other
parameters are stored as
raising arguments in the exception. Usually
the parameters is an exception message, but it's left to the exception class
implementation.
If the exception class name starts with a "+", then the
"Dancer::Exception::" won't be added. This allows one to build their
own exception class hierarchy, but you should first look at
"register_exception" before implementing your own class hierarchy.
If you really wish to build your own exception class hierarchy, we recommend
that all exceptions inherit of Dancer::Exception::. Or at least it should
implement its methods.
The exception class can also be written as words separated by underscores, it'll
be camelized automatically. So 'Exception::Foo' and 'exception_foo' are
equivalent. Be careful, 'MyException' can't be written 'myexception', as it
would be camelized into 'Myexception'.
register_exception¶
This method allows one to register custom exceptions, usable by Dancer users in
their route code (actually pretty much everywhere).
# simple exception
register_exception ('InvalidCredentials',
message_pattern => "invalid credentials : %s",
);
This registers a new custom exception. To use it, do:
raise InvalidCredentials => "user Herbert not found";
The exception message can be retrieved with the
"$exception->message" method, and we'll be "invalid
credentials : user Herbert not found" (see methods in
Dancer::Exception::Base)
# complex exception
register_exception ('InvalidLogin',
composed_from => [qw(Fatal InvalidCredentials)],
message_pattern => "wrong login or password",
);
In this example, the "InvalidLogin" is built as a composition of the
"Fatal" and "InvalidCredentials" exceptions. See the
"does" method in Dancer::Exception::Base.
registered_exceptions¶
my @exception_classes = registered_exceptions;
Returns the list of exception class names. It will list core exceptions
"and" custom exceptions (except the one you've registered with a
leading "+", see "register_exception"). The list is
sorted.
GLOBAL VARIABLE¶
$Dancer::Exception::Verbose¶
When set to 1, exceptions will stringify with a long stack trace. This variable
is similar to $Carp::Verbose. I recommend you use it like that:
local $Dancer::Exception::Verbose;
$Dancer::Exception::Verbose = 1;
All the Carp global variables can also be used to alter the stacktrace
generation.
AUTHOR¶
Dancer Core Developers
COPYRIGHT AND LICENSE¶
This software is copyright (c) 2010 by Alexis Sukrieh.
This is free software; you can redistribute it and/or modify it under the same
terms as the Perl 5 programming language system itself.