Can a log4j (or other Java logger) Appender accept or access request context objects?

I am currently writing a web service using Restlet, and logging with slf4j in front of log4j. Currently I have standard log4j Appenders in place for logging to files. What I was trying to do is also include log output in the HTTP Response, using a custom Appender.

The issue I am seeing is that Appenders by default have no ability to access the context of the request being made, which makes sense since theoretically the request could finish 开发者_高级运维before an asynchronous Appender gets around to executing. I am still curious as to whether this is possible, perhaps by making the Appender synchronous and passing a Response object with the log call. I can't find a way that log4j would support this, would another framework like logback? I wouldn't necessarily use this method in the end because of the performance implications, but still I am curious.

FYI my current workaround is a custom log method which adds the entry to the Response, then calls the slf4j method for standard logging. Downside to this is having to use a custom method, and I only get log entries for code I control (libraries I'm using that just use Appenders don't get logged to Response)

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Most Appender operations don't happen asynchronously. I'm not sure how slf4j changes that equation, but you can certainly build an Appender that knows how to format any given object into a LogEvent. Asynchronicity shouldn't really matter, since the request context should be unchanging once it arrives in the Appender - holding a reference should be sufficient.

How do you access the Context of the request outside of the Log4J code?

I would probably just solve this using a custom appender that knew how to specially handle a Context for your logging purposes.