HTML::Mason::Exceptions - Exception objects thrown by Mason
use HTML::Mason::Exceptions ( abbr => [ qw(system_error) ] );
open FH, 'foo' or system_error "cannot open foo: $!";
This module creates the hierarchy of exception objects used by Mason, and
provides some extra methods for them beyond those provided by
"Exception::Class"
When this module is imported, it is possible to specify a list of abbreviated
function names that you want to use to throw exceptions. In the SYNOPSIS
example, we use the "system_error" function
to throw a "HTML::Mason::Exception::System"
exception.
These abbreviated functions do not allow you to set additional
fields in the exception, only the message.
- HTML::Mason::Exception
- This is the parent class for all exceptions thrown by Mason. Mason
sometimes throws exceptions in this class when we could not find a better
category for the message.
Abbreviated as "error"
- HTML::Mason::Exception::Abort
- The "$m->abort" method was called.
Exceptions in this class contain the field
"aborted_value".
- HTML::Mason::Exception::Decline
- The "$m->decline" method was called.
Exceptions in this class contain the field
"declined_value".
- HTML::Mason::Exception::Compilation
- An exception occurred when attempting to
"eval" an existing object file.
Exceptions in this class have the field
"filename", which indicates what file
contained the code that caused the error.
Abbreviated as
"compilation_error".
- HTML::Mason::Exception::Compiler
- The compiler threw an exception because it received incorrect input. For
example, this would be thrown if the lexer told the compiler to initialize
compilation while it was in the middle of compiling another component.
Abbreviated as
"compiler_error".
- HTML::Mason::Exception::Compilation::IncompatibleCompiler
- A component was compiled by a compiler or lexer with incompatible options.
This is used to tell Mason to recompile a component.
Abbreviated as
"wrong_compiler_error".
- HTML::Mason::Exception::Params
- Invalid parameters were passed to a method or function.
Abbreviated as
"param_error".
- HTML::Mason::Exception::Syntax
- This exception indicates that a component contained invalid syntax.
Exceptions in this class have the fields
"source_line", which is the actual
source where the error was found,
"comp_name", and
"line_number".
Abbreviated as
"syntax_error".
- HTML::Mason::Exception::System
- A system call of some sort, such as a file open, failed.
Abbreviated as
"system_error".
- HTML::Mason::Exception::TopLevelNotFound
- The requested top level component could not be found.
Abbreviated as
"top_level_not_found_error".
- HTML::Mason::VirtualMethod
- Some piece of code attempted to call a virtual method which was not
overridden.
Abbreviated as
"virtual_error"
Some of the exceptions mentioned above have additional fields, which are
available via accessors. For example, to get the line number of an
"HTML::Mason::Exception::Syntax" exception,
you call the "line_number" method on the
exception object.
All of the Mason exceptions implement the following methods:
- as_brief
- This simply returns the exception message, without any trace
information.
- as_line
- This returns the exception message and its trace information, all on a
single line with tabs between the message and each frame of the stack
trace.
- as_text
- This returns the exception message and stack information, with each frame
on a separate line.
- as_html
- This returns the exception message and stack as an HTML page.
Each of these methods corresponds to a valid error_format
parameter for the Request object such as
"text" or
"html".
You can create your own method in the
"HTML::Mason::Exception" namespace, such
as "as_you_wish", in which case you could
set this parameter to "you_wish". This method will receive a
single argument, the exception object, and is expected to return some sort
of string containing the formatted error message.
This module also exports the
"isa_mason_exception" function. This
function takes the exception object and an optional string parameter
indicating what subclass to check for.
So it can be called either as:
if ( isa_mason_exception($@) ) { ... }
or
if ( isa_mason_exception($@, 'Syntax') ) { ... }
Note that when specifying a subclass you should not include the
leading "HTML::Mason::Exception::" portion of the class name.