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.IX Title "MDC 3"
.TH MDC 3 "2010-10-27" "perl v5.8.8" "User Contributed Perl Documentation"
.SH "NAME"
Log::Log4perl::MDC \- Mapped Diagnostic Context
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Log::Log4perl allows loggers to maintain global thread-specific data, 
called the Nested Diagnostic Context (\s-1NDC\s0) and 
Mapped Diagnostic Context (\s-1MDC\s0).
.PP
The \s-1MDC\s0 is a simple thread-specific hash table, in which the application
can stuff values under certain keys and retrieve them later
via the \f(CW"%X{key}"\fR placeholder in 
\&\f(CW\*(C`Log::Log4perl::Layout::PatternLayout\*(C'\fRs.
.ie n .IP "Log::Log4perl::MDC\->put($key, $value);" 4
.el .IP "Log::Log4perl::MDC\->put($key, \f(CW$value\fR);" 4
.IX Item "Log::Log4perl::MDC->put($key, $value);"
Store a value \f(CW$value\fR under key \f(CW$key\fR in the map.
.ie n .IP "my $value = Log::Log4perl::MDC\->get($key);" 4
.el .IP "my \f(CW$value\fR = Log::Log4perl::MDC\->get($key);" 4
.IX Item "my $value = Log::Log4perl::MDC->get($key);"
Retrieve the content of the map under the specified key.
Typically done by \f(CW%X{key}\fR in
\&\f(CW\*(C`Log::Log4perl::Layout::PatternLayout\*(C'\fR.
If no value exists to the given key, \f(CW\*(C`undef\*(C'\fR is returned.
.ie n .IP "my $text\fR = Log::Log4perl::MDC\->\fIremove();" 4
.el .IP "my \f(CW$text\fR = Log::Log4perl::MDC\->\fIremove()\fR;" 4
.IX Item "my $text = Log::Log4perl::MDC->remove();"
Delete all entries from the map.
.IP "Log::Log4perl::MDC\->\fIget_context()\fR;" 4
.IX Item "Log::Log4perl::MDC->get_context();"
Returns a reference to the hash table.
.PP
Please note that all of the methods above are class methods, there's no
instances of this class. Since the thread model in perl 5.8.0 is
\&\*(L"no shared data unless explicetly requested\*(R" the data structures
used are just global (and therefore thread\-specific).
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright 2002\-2009 by Mike Schilli <m@perlmeister.com> 
and Kevin Goess <cpan@goess.org>.
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.