METHODS

"new"

Constructor, typically called like

    my $config_parser = SomeConfigParser->new(
        file => $file,
    );

    my $data = $config_parser->parse();
    

Instead of "file", the derived class "SomeConfigParser" may define any type of configuration input medium (e.g. "url => 'http://foobar'"). It just has to make sure its "parse()" method will later pull the input data from the medium specified.

The base class accepts a filename or a reference to an array of text lines:

"parse"

Virtual method, needs to be defined by the derived class.

Parser requirements

• If the parser provides variable substitution functionality, it has to implement it.
• The parser's "parse()" method returns a reference to a hash of hashes (HoH). The top-most hash contains the top-level keywords ("category", "appender") as keys, associated with values which are references to more deeply nested hashes.
• The "log4perl." prefix (e.g. as used in the PropertyConfigurator class) is stripped, it's not part in the HoH structure.
• Each Log4perl config value is indicated by the "value" key, as in

      $data->{category}->{Bar}->{Twix}->{value} = "WARN, Logfile"
      

EXAMPLES

    log4perl.category.Bar.Twix        = WARN, Screen
    log4perl.appender.Screen          = Log::Log4perl::Appender::File
    log4perl.appender.Screen.filename = test.log
    log4perl.appender.Screen.layout   = Log::Log4perl::Layout::SimpleLayout

needs to be transformed by the parser's "parse()" method into this data structure:

    { appender => {
        Screen  => {
          layout => { 
            value  => "Log::Log4perl::Layout::SimpleLayout" },
            value  => "Log::Log4perl::Appender::Screen",
        },
      },
      category => { 
        Bar => { 
          Twix => { 
            value => "WARN, Screen" } 
        } }
    }

For a full-fledged example, check out the sample YAML parser implementation in "eg/yamlparser". It uses a simple YAML syntax to specify the Log4perl configuration to illustrate the concept.