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Exception::Base.3pm

NAME

Exception::Base - Lightweight exceptions

SYNOPSIS

   # Use module and create needed exceptions
   use Exception::Base
      'Exception::Runtime',              # create new module
      'Exception::System',               # load existing module
      'Exception::IO',          => {
          isa => 'Exception::System' },  # create new based on existing
      'Exception::FileNotFound' => {
          isa => 'Exception::IO',        # create new based on previous
          message => 'File not found',   # override default message
          has => [ 'filename' ],         # define new rw attribute
          string_attributes => [ 'message', 'filename' ],
      };                                 # output message and filename
 
   # eval is used as "try" block
   eval {
     open my $file, '/etc/passwd'
       or Exception::FileNotFound->throw(
             message=>'Something wrong',
             filename=>'/etc/passwd');
   };
   # standard syntax for older Perl
   if ($@) {
     my $e = Exception::Base->catch;   # convert $@ into exception
     if ($e->isa('Exception::IO')) { warn "IO problem"; }
     elsif ($e->isa('Exception::Eval')) { warn "eval died"; }
     elsif ($e->isa('Exception::Runtime')) { warn "some runtime was caught"; }
     elsif ($e->matches({value=>9})) { warn "something happened"; }
     elsif ($e->matches(qr/^Error/)) { warn "some error based on regex"; }
     else { $e->throw; } # rethrow the exception
   }
   # alternative syntax for Perl 5.10
   use feature 'switch';
   if ($@) {
     given (my $e = Exception::Base->catch) {
       when (['Exception::IO']) { warn "IO problem"; }
       when (['Exception::Eval']) { warn "eval died"; }
       when (['Exception::Runtime']) { warn "some runtime was caught"; }
       when ({value=>9}) { warn "something happened"; }
       when (qr/^Error/) { warn "some error based on regex"; }
       default { $e->throw; } # rethrow the exception
     }
   }
 
   # $@ has to be recovered ASAP!
   eval { die "this die will be caught" };
   my $e = Exception::Base->catch;
   eval { die "this die will be ignored" };
   if ($e) {
      (...)
   }
 
   # the exception can be thrown later
   my $e = Exception::Base->new;
   # (...)
   $e->throw;
 
   # ignore our package in stack trace
   package My::Package;
   use Exception::Base '+ignore_package' => __PACKAGE__;
 
   # define new exception in separate module
   package Exception::My;
   use Exception::Base (__PACKAGE__) => {
       has => ['myattr'],
   };
 
   # run Perl with changed verbosity for debugging purposes
   $ perl -MException::Base=verbosity,4 script.pl
 
 

DESCRIPTION

This class implements a fully OO exception mechanism similar to Exception::Class or Class::Throwable. It provides a simple interface allowing programmers to declare exception classes. These classes can be thrown and caught. Each uncaught exception prints full stack trace if the default verbosity is uppered for debugging purposes.

The features of "Exception::Base":

•

fast implementation of the exception class

•

fully OO without closures and source code filtering

•

does not mess with $SIG{__DIE__} and $SIG{__WARN__}

•

no external modules dependencies, requires core Perl modules only

•

the default behaviour of exception class can be changed globally or just for the thrown exception

•

matching the exception by class, message or other attributes

•

matching with string, regex or closure function

•

creating automatically the derived exception classes (``use'' in perlfunc interface)

•

easly expendable, see Exception::System class for example

•

prints just an error message or dumps full stack trace

•

can propagate (rethrow) an exception

•

can ignore some packages for stack trace output

•

some defaults (i.e. verbosity) can be different for different exceptions

IMPORTS

"use Exception::Base 'attribute' =" value;>

Changes the default value for attribute. If the attribute name has no special prefix, its default value is replaced with a new value.

   use Exception::Base verbosity => 4;
 
 

If the attribute name starts with ""+"`` or ''"-"" then the new value is based on previous value:

•

If the original value was a reference to array, the new value can be included or removed from original array. Use array reference if you need to add or remove more than one element.

   use Exception::Base
       "+ignore_packages" => [ __PACKAGE__, qr/^Moose::/ ],
       "-ignore_class" => "My::Good::Class";
 
 

•

If the original value was a number, it will be incremeted or decremented by the new value.

   use Exception::Base "+ignore_level" => 1;
 
 

•

If the original value was a string, the new value will be included.

   use Exception::Base "+message" => ": The incuded message";
 
 

"use Exception::Base 'Exception', ...;"

Loads additional exception class module. If the module is not available, creates the exception class automatically at compile time. The newly created class will be based on "Exception::Base" class.

   use Exception::Base qw{ Exception::Custom Exception::SomethingWrong };
   Exception::Custom->throw;
 
 

"use Exception::Base 'Exception' =" { isa => BaseException, version => version, ... };>

Loads additional exception class module. If the module's version is lower than given parameter or the module can't be loaded, creates the exception class automatically at compile time. The newly created class will be based on given class and has the given $VERSION variable.

isa

The newly created class will be based on given class.

   use Exception::Base
     'Exception::My',
     'Exception::Nested' => { isa => 'Exception::My };
 
 

version

The class will be created only if the module's version is lower than given parameter and will have the version given in the argument.

   use Exception::Base
     'Exception::My' => { version => 1.23 };
 
 

has

The class will contain new rw attibute (if parameter is a string) or new rw attributes (if parameter is a reference to array of strings) or new rw or ro attributes (if parameter is a reference to hash of array of strings with rw and ro as hash key).

   use Exception::Base
     'Exception::Simple' => { has => 'field' },
     'Exception::More' => { has => [ 'field1', 'field2' ] },
     'Exception::Advanced' => { has => {
         ro => [ 'field1', 'field2' ],
         rw => [ 'field3' ]
     } };
 
 

message

verbosity

max_arg_len

max_arg_nums

max_eval_len

other attribute having default property

The class will have the default property for the given attribute.

   use Exception::Base
     'Exception::WithDefault' => { message => 'Default message' },
     'Exception::Reason' => {
         has => [ 'reason' ],
         string_attributes => [ 'message', 'reason' ] };
 
 

CONSTANTS

ATTRS

Declaration of class attributes as reference to hash.

The attributes are listed as name => {properties}, where properties is a list of attribute properties:

is

Can be 'rw' for read-write attributes or 'ro' for read-only attributes. The attribute is read-only and does not have an accessor created if 'is' property is missed.

default

Optional property with the default value if the attribute value is not defined.

The read-write attributes can be set with "new" constructor. Read-only attributes and unknown attributes are ignored.
The constant have to be defined in derivered class if it brings additional attributes.

   package Exception::My;
   our $VERSION = 0.01;
   use base 'Exception::Base';
 
   # Define new class attributes
   use constant ATTRS => {
     %{Exception::Base->ATTRS},       # base's attributes have to be first
     readonly  => { is=>'ro' },                   # new ro attribute
     readwrite => { is=>'rw', default=>'blah' },  # new rw attribute
   };
 
   package main;
   use Exception::Base ':all';
   eval {
     Exception::My->throw( readwrite => 2 );
   };
   if ($@) {
     my $e = Exception::Base->catch;
     print $e->readwrite;                # = 2
     print $e->defaults->{readwrite};    # = "blah"
   }
 
 

ATTRIBUTES

Class attributes are implemented as values of blessed hash. The attributes are also available as accessors methods.

message (rw, default: 'Unknown exception')

Contains the message of the exception. It is the part of the string representing the exception object.

   eval { Exception::Base->throw( message=>"Message" ); };
   print $@->message if $@;
 
 

value (rw, default: 0)

Contains the value which represents numeric value of the exception object in numeric context.

   eval { Exception::Base->throw( value=>2 ); };
   print "Error 2" if $@ == 2;
 
 

verbosity (rw, default: 2)

Contains the verbosity level of the exception object. It allows to change the string representing the exception object. There are following levels of verbosity:

0

Empty string

1

  Message
 
 

2

  Message at %s line %d.
 
 

The same as the standard output of die() function. It doesn't include ``at %s line %d.'' string if message ends with "\n" character. This is the default option.

3

  Class: Message at %s line %d
          %c_ = %s::%s() called in package %s at %s line %d
          ...propagated in package %s at %s line %d.
  ...
 
 

The output contains full trace of error stack without first "ignore_level" lines and those packages which are listed in "ignore_package" and "ignore_class" settings.

4

The output contains full trace of error stack. In this case the "ignore_level", "ignore_package" and "ignore_class" settings are meaning only for first line of exception's message.

If the verbosity is undef, then the default verbosity for exception objects is used.
If the verbosity set with constructor ("new" or "throw") is lower than 3, the full stack trace won't be collected.
If the verbosity is lower than 2, the full system data (time, pid, tid, uid, euid, gid, egid) won't be collected.
This setting can be changed with import interface.

   use Exception::Base verbosity => 4;
 
 

It can be also changed for Perl interpreter instance, i.e. for debugging purposes.

   sh$ perl -MException::Base=verbosity,4 script.pl
 
 

ignore_package (rw)

Contains the name (scalar or regexp) or names (as references array) of packages which are ignored in error stack trace. It is useful if some package throws an exception but this module shouldn't be listed in stack trace.

   package My::Package;
   use Exception::Base;
   sub my_function {
     do_something() or throw Exception::Base ignore_package=>__PACKAGE__;
     throw Exception::Base ignore_package => [ "My", qr/^My::Modules::/ ];
   }
 
 

This setting can be changed with import interface.

   use Exception::Base ignore_package => __PACKAGE__;
 
 

ignore_class (rw)

Contains the name (scalar) or names (as references array) of packages which are base classes for ignored packages in error stack trace. It means that some packages will be ignored even the derived class was called.

   package My::Package;
   use Exception::Base;
   Exception::Base->throw( ignore_class => "My::Base" );
 
 

This setting can be changed with import interface.

   use Exception::Base ignore_class => "My::Base";
 
 

ignore_level (rw)

Contains the number of level on stack trace to ignore. It is useful if some package throws an exception but this module shouldn't be listed in stack trace. It can be used with or without ignore_package attribute.

   # Convert warning into exception. The signal handler ignores itself.
   use Exception::Base 'Exception::My::Warning';
   $SIG{__WARN__} = sub {
     Exception::My::Warning->throw( message => $_[0], ignore_level => 1 );
   };
 
 

time (ro)

Contains the timestamp of the thrown exception. Collected if the verbosity on throwing exception was greater than 1.

   eval { Exception::Base->throw( message=>"Message" ); };
   print scalar localtime $@->time;
 
 

pid (ro)

Contains the PID of the Perl process at time of thrown exception. Collected if the verbosity on throwing exception was greater than 1.

   eval { Exception::Base->throw( message=>"Message" ); };
   kill 10, $@->pid;
 
 

tid (ro)

Constains the tid of the thread or undef if threads are not used. Collected if the verbosity on throwing exception was greater than 1.

uid (ro)

euid (ro)

gid (ro)

egid (ro)

Contains the real and effective uid and gid of the Perl process at time of thrown exception. Collected if the verbosity on throwing exception was greater than 1.

caller_stack (ro)

Contains the error stack as array of array with informations about caller functions. The first 8 elements of the array's row are the same as first 8 elements of the output of "caller" function. Further elements are optional and are the arguments of called function. Collected if the verbosity on throwing exception was greater than 1. Contains only the first element of caller stack if the verbosity was lower than 3.

If the arguments of called function are references and "Scalar::Util::weaken" function is available then reference is weakened.

   eval { Exception::Base->throw( message=>"Message" ); };
   ($package, $filename, $line, $subroutine, $hasargs, $wantarray,
   $evaltext, $is_require, @args) = $@->caller_stack->[0];
 
 

propagated_stack (ro)

Contains the array of array which is used for generating ``...propagated at'' message. The elements of the array's row are the same as first 3 elements of the output of "caller" function.

max_arg_len (rw, default: 64)

Contains the maximal length of argument for functions in backtrace output. Zero means no limit for length.

   sub a { Exception::Base->throw( max_arg_len=>5 ) }
   a("123456789");
 
 

max_arg_nums (rw, default: 8)

Contains the maximal number of arguments for functions in backtrace output. Zero means no limit for arguments.

   sub a { Exception::Base->throw( max_arg_nums=>1 ) }
   a(1,2,3);
 
 

max_eval_len (rw, default: 0)

Contains the maximal length of eval strings in backtrace output. Zero means no limit for length.

   eval "Exception->throw( max_eval_len=>10 )";
   print "$@";
 
 

defaults

Meta-attribute contains the list of default values.

   my $e = Exception::Base->new;
   print defined $e->{verbosity}
     ? $e->{verbosity}
     : $e->{defaults}->{verbosity};
 
 

default_attribute (default: 'message')

Meta-attribute contains the name of the default attribute. This attribute will be set for one argument throw method. This attribute has meaning for derived classes.

   use Exception::Base 'Exception::My' => {
       has => 'myattr',
       default_attribute => 'myattr',
   };
 
   eval { Exception::My->throw("string") };
   print $@->myattr;    # "string"
 
 

numeric_attribute (default: 'value')

Meta-attribute contains the name of the attribute which contains numeric value of exception object. This attribute will be used for representing exception in numeric context.

   use Exception::Base 'Exception::My' => {
       has => 'myattr',
       numeric_attribute => 'myattr',
   };
 
   eval { Exception::My->throw(myattr=>123) };
   print 0 + $@;    # 123
 
 

eval_attribute (default: 'message')

Meta-attribute contains the name of the attribute which is filled if error stack is empty. This attribute will contain value of $@ variable. This attribute has meaning for derived classes.

   use Exception::Base 'Exception::My' => {
       has => 'myattr',
       eval_attribute => 'myattr'
   };
 
   eval { die "string" };
   print $@->myattr;    # "string"
 
 

string_attributes (default: ['message'])

Meta-attribute contains the array of names of attributes with defined value which are joined to the string returned by "to_string" method. If none of attributes are defined, the string is created from the first default value of attributes listed in the opposite order.

   use Exception::Base 'Exception::My' => {
       has => 'myattr',
       myattr => 'default',
       string_attributes => ['message', 'myattr'],
   };
 
   eval { Exception::My->throw( message=>"string", myattr=>"foo" ) };
   print $@->myattr;    # "string: foo"
 
   eval { Exception::My->throw() };
   print $@->myattr;    # "default"
 
 

OVERLOADS

Boolean context

True value. See "to_bool" method.

   eval { Exception::Base->throw( message=>"Message", value=>123 ) };
   if ($@) {
      # the exception object is always true
   }
 
 

Numeric context

Content of attribute pointed by "numeric_attribute" attribute. See "to_number" method.

   eval { Exception::Base->throw( message=>"Message", value=>123 ) };
   print 0+$@;           # 123
 
 

String context

Content of attribute which is combined from "string_attributes" attributes with additional informations, depended on "verbosity" setting. See "to_string" method.

   eval { Exception::Base->throw( message=>"Message", value=>123 ) };
   print "$@";           # "Message at -e line 1.\n"
 
 

"~~"

Smart matching operator. See "matches" method.

   eval { Exception::Base->throw( message=>"Message", value=>123 ) };
   print $@ ~~ "Message";                          # 1
   print $@ ~~ qr/message/i;                       # 1
   print $@ ~~ ['Exception::Base'];                # 1
   print $@ ~~ 123;                                # 1
   print $@ ~~ {message=>"Message", value=>123};   # 1
 
 

CONSTRUCTORS

new([%args])

Creates the exception object, which can be thrown later. The system data attributes like "time", "pid", "uid", "gid", "euid", "egid" are not filled.

If the key of the argument is read-write attribute, this attribute will be filled. Otherwise, the argument will be ignored.

   $e = Exception::Base->new(
            message=>"Houston, we have a problem",
            unknown_attr => "BIG"
        );
   print $e->{message};
 
 

The constructor reads the list of class attributes from ATTRS constant function and stores it in the internal cache for performance reason. The defaults values for the class are also stored in internal cache.

"CLASS"->throw([%args]])

Creates the exception object and immediately throws it with "die" system function.

   open my $fh, $file
     or Exception::Base->throw( message=>"Can not open file: $file" );
 
 

The "throw" is also exported as a function.

   open my $fh, $file
     or throw 'Exception::Base' => message=>"Can not open file: $file";
 
 

The "throw" can be also used as a method.

METHODS

$obj->throw([%args])

Immediately throws exception object. It can be used for rethrowing existing exception object. Additional arguments will override the attributes in existing exception object.

   $e = Exception::Base->new;
   # (...)
   $e->throw( message=>"thrown exception with overriden message" );
 
   eval { Exception::Base->throw( message=>"Problem", value=>1 ) };
   $@->throw if $@->value;
 
 

$obj->throw(message, [%args])

If the number of args list for arguments is odd, the first argument is a message. This message can be overriden by message from args list.

   Exception::Base->throw( "Problem", message=>"More important" );
   eval { die "Bum!" };
   Exception::Base->throw( $@, message=>"New message" );
 
 

CLASS->throw($exception, [%args])

Immediately rethrows an existing exception object as an other exception class.

   eval { open $f, "w", "/etc/passwd" or Exception::System->throw };
   # convert Exception::System into Exception::Base
   Exception::Base->throw($@);
 
 

CLASS->catch

The exception is recovered from $@ variable and method returns an exception object if exception is caught or undefined value otherwise. The $@ variable is replaced with empty string to avoid endless loop.

   eval { Exception::Base->throw; };
   if ($@) {
       my $e = Exception::Base->catch;
       print $e->to_string;
   }
 
 

If the value is not empty and does not contain the "Exception::Base" object, new exception object is created with class CLASS and its message is based on previous value with removed " at file line 123." string and the last end of line (LF).

   eval { die "Died\n"; };
   my $e = Exception::Base->catch;
   print ref $e;   # "Exception::Base"
 
 

matches(that)

Checks if the exception object matches the given argument. The "matches" method overloads "~~" smart matching operator, so it can be used with "given" keyword.

   my $e = Exception::Base->new( message=>"Message", value=>123 );
   use feature 'switch';
   given ($e) {
     when( "Message" ) { ... }                             # matches
     when( qr/message/i ) { ... }                          # matches
     when( ["Exception::Base"] ) { ... }                   # matches
     when( ["Exception::Foo", "Exception::Bar"] ) { ... }  # doesn't
     when( { message=>"Message" } ) { ... }                # matches
     when( { value=>123 } ) { ... }                        # matches
     when( { message=>"Message", value=>45 } ) { ... }     # doesn't
     when( { uid=>0 } ) { ... }  # matches if runs with root privileges
   }
 
 

If the argument is a reference to array, it is checked if the object is a given class.

   use Exception::Base
     'Exception::Simple',
     'Exception::Complex' => { isa => 'Exception::Simple };
   eval { Exception::Complex->throw() };
   print $@->matches( ['Exception::Base'] );                    # matches
   print $@->matches( ['Exception::Simple', 'Exception::X'] );  # matches
   print $@->matches( ['NullObject'] );                         # doesn't
 
 

If the argument is a reference to hash, attributes of the exception object is matched.

   eval { Exception::Base->throw( message=>"Message", value=>123 ) };
   print $@->matches( { message=>"Message" } );             # matches
   print $@->matches( { value=>123 } );                     # matches
   print $@->matches( { message=>"Message", value=>45 } );  # doesn't
 
 

If the argument is a single string, regexp or code reference or is undefined, the default attribute of the exception object is matched (usually it is a ``message'' attribute).

   eval { Exception::Base->throw( message=>"Message" ) };
   print $@->matches( "Message" );                          # matches
   print $@->matches( qr/Message/ );                        # matches
   print $@->matches( qr/[0-9]/ );                          # doesn't
   print $@->matches( sub{/Message/} );                     # matches
   print $@->matches( sub{0} );                             # doesn't
   print $@->matches( undef );                              # doesn't
 
 

If argument is a numeric value, the argument matches if "value" attribute matches.

   eval { Exception::Base->throw( value=>123, message=>456 ) } );
   print $@->matches( 123 );                                # matches
   print $@->matches( 456 );                                # doesn't
 
 

The "match" method matches for special keywords:

-isa

Matches if the object is a given class.

   eval { Exception::Base->new( message=>"Message" ) };
   print $@->matches( { -isa=>"Exception::Base" } );            # matches
   print $@->matches( { -isa=>["X::Y", "Exception::Base"] } );  # matches
 
 

-has

Matches if the object has a given attribute.

   eval { Exception::Base->new( message=>"Message" ) };
   print $@->matches( { -has=>"Message" } );                    # matches
 
 

-default

Matches against the default attribute, usually the "message" attribute.

   eval { Exception::Base->new( message=>"Message" ) };
   print $@->matches( { -default=>"Message" } );                # matches
 
 

to_string

Returns the string representation of exception object. It is called automatically if the exception object is used in string scalar context. The method can be used explicity.

   eval { Exception::Base->throw; };
   $@->{verbosity} = 1;
   print "$@";
   $@->verbosity = 4;
   print $@->to_string;
 
 

to_number

Returns the numeric representation of exception object. It is called automatically if the exception object is used in numeric scalar context. The method can be used explicity.

   eval { Exception::Base->throw( value => 42 ); };
   print 0+$@;           # 42
   print $@->to_number;  # 42
 
 

to_bool

Returns the boolean representation of exception object. It is called automatically if the exception object is used in boolean context. The method can be used explicity.

   eval { Exception::Base->throw; };
   print "ok" if $@;           # ok
   print "ok" if $@->to_bool;  # ok
 
 

get_caller_stacktrace

Returns an array of strings or string with caller stack trace. It is implicity used by "to_string" method.

PROPAGATE

Checks the caller stack and fills the "propagated_stack" attribute. It is usually used if "die" system function was called without any arguments.

package

Returns the package name of the subroutine which thrown an exception.

file

Returns the file name of the subroutine which thrown an exception.

line

Returns the line number for file of the subroutine which thrown an exception.

subroutine

Returns the subroutine name which thrown an exception.

PRIVATE METHODS

_collect_system_data

Collects system data and fills the attributes of exception object. This method is called automatically if exception if thrown or created by "new" constructor. It can be overriden by derived class.

   package Exception::Special;
   use base 'Exception::Base';
   use constant ATTRS => {
     %{Exception::Base->ATTRS},
     'special' => { is => 'ro' },
   };
   sub _collect_system_data {
     my $self = shift;
     $self->SUPER::_collect_system_data(@_);
     $self->{special} = get_special_value();
     return $self;
   }
   BEGIN {
     __PACKAGE__->_make_accessors;
   }
   1;
 
 

Method returns the reference to the self object.

_make_accessors

Creates accessors for each attribute. This static method should be called in each derived class which defines new attributes.

   package Exception::My;
   # (...)
   BEGIN {
     __PACKAGE__->_make_accessors;
   }
 
 

PRIVATE FUNCTIONS

_qualify_to_ref

See "Symbol::qualify_to_ref" function.

SEE ALSO

There are more implementation of exception objects available on CPAN. Please note that Perl has built-in implementation of pseudo-exceptions:

   eval { die { message => "Pseudo-exception", package => __PACKAGE__,
                file => __FILE__, line => __LINE__ };
   };
   if ($@) {
     print $@->{message}, " at ", $@->{file}, " in line ", $@->{line}, ".\n";
   }
 
 

The more complex implementation of exception mechanism provides more features.

Error

Complete implementation of try/catch/finally/otherwise mechanism. Uses nested closures with a lot of syntactic sugar. It is slightly faster than "Exception::Base" module for failure scenario and is much slower for success scenario. It doesn't provide a simple way to create user defined exceptions. It doesn't collect system data and stack trace on error.

Exception::Class

More perl-ish way to do OO exceptions. It is similar to "Exception::Base" module and provides similar features but it is 10x slower for failure scenario.

Exception::Class::TryCatch

Additional try/catch mechanism for Exception::Class. It is 15x slower for success scenario.

Class::Throwable

Elegant OO exceptions similar to Exception::Class and "Exception::Base". It might be missing some features found in "Exception::Base" and Exception::Class.

Exceptions

Not recommended. Abadoned. Modifies %SIG handlers.

The "Exception::Base" does not depend on other modules like Exception::Class and it is more powerful than Class::Throwable. Also it does not use closures as Error and does not polute namespace as Exception::Class::TryCatch. It is also much faster than Exception::Class::TryCatch and Error for success scenario.

The "Exception::Base" is also a base class for enchanced classes:

Exception::System

The exception class for system or library calls which modifies $! variable.

Exception::Died

The exception class for eval blocks with simple ``die'' in perlfunc. It can also handle $SIG{__DIE__} hook and convert simple ``die'' in perlfunc into an exception object.

Exception::Warning

The exception class which handle $SIG{__WARN__} hook and convert simple ``warn'' in perlfunc into an exception object.

EXAMPLES

New exception classes

The "Exception::Base" module allows to create new exception classes easly. You can use ``import'' in perlfunc interface or base module to do it.

The ``import'' in perlfunc interface allows to create new class with new read-write attributes.

   package Exception::Simple;
   use Exception::Base (__PACKAGE__) => {
     has => qw{ reason method },
     string_attributes => qw{ message reason method },
   };
 
 

For more complex exceptions you can redefine "ATTRS" constant.

   package Exception::Complex;
   use base 'Exception::Base';
   use constant ATTRS => {
     %{ Exception::Base->ATTRS },     # SUPER::ATTRS
     hostname => { is => 'ro' },
     string_attributes => qw{ hostname message },
   };
   sub _collect_system_data {
     my $self = shift;
     my $hostname = `hostname`;
     chomp $hostname;
     $self->{hostname} = $hostname;
     return $self->SUPER::_collect_system_data(@_);
   }
 
 

PERFORMANCE

There are two scenarios for ``eval'' in perlfunc block: success or failure. Success scenario should have no penalty on speed. Failure scenario is usually more complex to handle and can be significally slower.

Any other code than simple "if ($@)" is really slow and shouldn't be used if speed is important. It means that Error and Exception::Class::TryCatch should be avoided as far as they are slow by design. The Exception::Class module doesn't use "if ($@)" syntax in its documentation so it was benchmarked with its default syntax, however it might be possible to convert it to simple "if ($@)".

The "Exception::Base" module was benchmarked with other implementations for simple try/catch scenario. The results (Perl 5.10 i686-linux-thread-multi) are following:

   -----------------------------------------------------------------------
   | Module                              | Success       | Failure       |
   -----------------------------------------------------------------------
   | eval/die string                     |      859644/s |      232952/s |
   -----------------------------------------------------------------------
   | eval/die object                     |      891294/s |      125992/s |
   -----------------------------------------------------------------------
   | Exception::Base eval/if             |      886204/s |        7585/s |
   -----------------------------------------------------------------------
   | Exception::Base eval/if verbosity=1 |      882376/s |       13778/s |
   -----------------------------------------------------------------------
   | Error                               |       85800/s |       19723/s |
   -----------------------------------------------------------------------
   | Class::Throwable                    |      878963/s |        7461/s |
   -----------------------------------------------------------------------
   | Exception::Class                    |      345114/s |        1278/s |
   -----------------------------------------------------------------------
   | Exception::Class::TryCatch          |      210389/s |        1259/s |
   -----------------------------------------------------------------------
 
 

The "Exception::Base" module was written to be as fast as it is possible. It does not use internally i.e. accessor functions which are slower about 6 times than standard variables. It is slower than pure die/eval because it is uses OO mechanisms which are slow in Perl. It can be a litte faster if some features are disables, i.e. the stack trace and higher verbosity.

You can find the benchmark script in this package distribution.

BUGS

If you find the bug, please report it.

AUTHOR

Piotr Roszatycki <dexter@debian.org>

LICENSE

Copyright (C) 2007, 2008 by Piotr Roszatycki <dexter@debian.org>.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

See <http://www.perl.com/perl/misc/Artistic.html>