Ceki usually is pretty responsive but I haven't seen him post for a few days. I'm guessing he must be taking a few days off. On Sep 9, 2009, at 7:04 PM, david_z wrote:
Hi, I'm new to logback and am in the process of evaluating as a replacement for log4j. A question was raised today at work regarding parameterized logging and the ability to modify logback to support java.text.MessageFormat style formatting in order to, for example, perform date or currency formatting: log.debug("myDate={0,date,MMM d}", myDate); log.debug("myAmount={0,number,currency}", myAmount);
or to defer array formatting, similar to the question I'm replying to above.
I appreciate the performance reasons for logback using {} replacement, but it seems like it should be possible to allow the user to provide an alternate formatting strategy if they so desire without negatively impacting the default's performance. Creating my own MessageConverter, as suggested above, to perform this formatting works fine, except the conversion is performed once per appender per event rather than just once per event.
Is there a better way to handle this custom formatting goal?
Actually, the MessageConverter doesn't do anything. All it does is retrieve the message as it was formatted by SLF4J. If you want to do formatting then create your own layout and/or converter.
If not, I have a suggestion for an enhancement. 1. Add a Formatter interface with the method String format(String messagePattern, Object[] argArray)
Converters implement String convert(ILoggingEvent event). If you look at how the pattern layout works, the parameters for the individual converters are passed to them.
2. The LoggingEvent would need access to the formatter. Ideally the Formatter could be configured via the config file as the Converters can be. I don't know enough about the source to flesh this part out well.
It works the other way around. The Converters have access to the logging event.
3. Modify getFormattedMessage() in the ILoggingEvent implementations public String getFormattedMessage() { if (formattedMessage != null) { return formattedMessage; } if (argumentArray != null) { if (formatter == null) { formattedMessage = MessageFormatter.arrayFormat(message, argumentArray); } else { formattedMessage = formatter.format(message, argumentArray); } } else { formattedMessage = message; } return formattedMessage; } What do you think?
1. I think Logback already provides a mechanism to do what you want. 2. I've been working on an enhancement to SLF4J and logback to support RFC 5424, the new IETF syslog specification. (See http://tools.ietf.org/html/rfc5424 ). In particular, the concept of Structured Data. You can play with what I have so far by checking it out from git://github.com/rgoers/slf4j.git and git://github.com/rgoers/logback.git. However, your idea of associating a converter with specific keys isn't something I had thought of but is worth considering, however I'd probably want to provide the definitions in the configuration, not in the actual logger calls. So far I've just focused on implementing something that adheres to the specification but I'd be interested in suggestions on how to improve it. Ralph Ralph