Re: Does log4cxx support variable-arguments?
I've defined my own logging macros that use , for example:
#include
// define logging macros using streams
#define LOG_LOG(_logger_, _level_, _message_) { \
if (_logger_->isEnabledFor(_level_)) {\
::std::stringstream sstr;\
sstr << _message_;\
_logger_->forcedLog(_level_, sstr.str(), LOG4CXX_LOCATION); } }
#define LOG_DEBUG(_logger_, _message_) LOG_LOG(_logger_,
::log4cxx::Level::DEBUG, _message_)
#define LOG_ERROR(_logger_, _message_) LOG_LOG(_logger_,
::log4cxx::Level::ERROR, _message_)
I can then use something like this:
LOG_ERROR("something nasty happened: status=" << status << ", value=" <<
value);
This has the effect of allowing multiple arguments (although in fact the
whole expression is a single macro argument).
Additionally, it allows easy use of objects ostream methods, to allow
them to describe their own state/value.
Hope this helps,
Derek
Curt Arnold wrote:
On Sep 17, 2006, at 1:58 PM, sishen wrote:
Hey. everyone.
I'm a new user of log4cxx. I want to know whether log4cxx support
variable argument?
I have found the maillist archive, but i haven't got any answers.
for example, like the macro:
#define LOG4CXX_DEBUG(logger, message)
it only takes two argument. And now i have to combine all argument
to a string.
This is not convenient. I think variable-argument is common for
logging system.
Any advice prefer, :)
No, however the message parameter can be an expression, the expression
could be a function that takes varargs or has multiple signatures.
The expression is only evaluated if the threshold is satisified, so if
you do something like:
LOG4CXX_INFO(logger, logfmt("%s %s %d", arg1, arg2, arg3));
The logfmt method would only be called if logger's threshold level is
INFO or above (where logfmt would be a method you defined that
returned std::string or std::wstring). The LOG4CXX_INFO are
preprocessor macros which handle all the details in passing the caller
information to the actual logger methods. If they were not
preprocessor macros the __LINE__ and __FILE__ would refer the the
location of the method implementation, not the caller. As
preprocessor macros, they do not have the ability to overload the
macro name with multiple definitions for different argument lists.
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Re: Does log4cxx support variable-arguments?
yeah. I prefer this way. That's what i want.Thanks all, :)On 9/18/06, Derek Baum <[EMAIL PROTECTED]
> wrote:I've defined my own logging macros that use , for example:
> #include >> // define logging macros using streams> #define LOG_LOG(_logger_, _level_, _message_) { \> if (_logger_->isEnabledFor(_level_)) {\> ::std::stringstream sstr;\
> sstr << _message_;\> _logger_->forcedLog(_level_, sstr.str(), LOG4CXX_LOCATION); } }>> #define LOG_DEBUG(_logger_, _message_) LOG_LOG(_logger_,> ::log4cxx::Level::DEBUG, _message_)
> #define LOG_ERROR(_logger_, _message_) LOG_LOG(_logger_,> ::log4cxx::Level::ERROR, _message_)I can then use something like this:LOG_ERROR("something nasty happened: status=" << status << ", value=" <<
value);This has the effect of allowing multiple arguments (although in fact thewhole _expression_ is a single macro argument).Additionally, it allows easy use of objects ostream methods, to allowthem to describe their own state/value.
Hope this helps,DerekCurt Arnold wrote:>> On Sep 17, 2006, at 1:58 PM, sishen wrote:>>> Hey. everyone. I'm a new user of log4cxx. I want to know whether log4cxx support
>> variable argument?>> I have found the maillist archive, but i haven't got any answers. for example, like the macro:>> #define LOG4CXX_DEBUG(logger, message)>>
>> it only takes two argument. And now i have to combine all argument>> to a string. This is not convenient. I think variable-argument is common for>> logging system.
>> Any advice prefer, :)>>> No, however the message parameter can be an _expression_, the _expression_> could be a function that takes varargs or has multiple signatures.> The _expression_ is only evaluated if the threshold is satisified, so if
> you do something like:>> LOG4CXX_INFO(logger, logfmt("%s %s %d", arg1, arg2, arg3));>> The logfmt method would only be called if logger's threshold level is> INFO or above (where logfmt would be a method you defined that
> returned std::string or std::wstring). The LOG4CXX_INFO are> preprocessor macros which handle all the details in passing the caller> information to the actual logger methods. If they were not> preprocessor macros the __LINE__ and __FILE__ would refer the the
> location of the method implementation, not the caller. As> preprocessor macros, they do not have the ability to overload the> macro name with multiple definitions for different argument lists.
The information transmitted is intended only for the person(s) or entityto which it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, ortaking of any action in reliance upon, this information by persons orentities other than the intended recipient is prohibited. If youreceived this in error, please contact the sender and delete the
material from any computer.Paremus Limited.107-111 Fleet Street, London EC4A 2AB. Phone number +44 20 7936 9098
