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:
"file"
Specifies a file which the "parse()" method later parses.
"text"
Specifies a reference to an array of scalars, representing configuration records (typically lines
of a file). Also accepts a simple scalar, which it splits at its newlines and transforms it into
an array:
my $config_parser = MyYAMLParser->new(
text => ['foo: bar',
'baz: bam',
],
);
my $data = $config_parser->parse();
If either "file" or "text" parameters have been specified in the constructor call, a later call to
the configurator's "text()" method will return a reference to an array of configuration text lines.
This will typically be used by the "parse()" method to process the input.
"parse"
Virtual method, needs to be defined by the derived class.
Parserrequirements
• 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
The following Log::Log4perl configuration:
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.
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