phpMan > perldoc > HTML::Mason::Exceptions

NAME
    HTML::Mason::Exceptions - Exception objects thrown by Mason

SYNOPSIS
      use HTML::Mason::Exceptions ( abbr => [ qw(system_error) ] );

      open FH, 'foo' or system_error "cannot open foo: $!";

DESCRIPTION
    This module creates the hierarchy of exception objects used by Mason, and provides some extra
    methods for them beyond those provided by "Exception::Class"

IMPORT
    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.

EXCEPTIONS
    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"

FIELDS
    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.

EXCEPTION METHODS
    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.

EXCEPTION CLASS CHECKING
    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.