folks resending this as I did not get any response - would appreciate your expert opinion on this!
Thank you in advance! Best Regards, Menon:) ------------------------------------------------------------- Ramakrishna M. Menon (A Rafi Fan - http://www.mohdrafi.com ) MBA, Berkeley Oracle Corp.-> (650) 506-2343 http://websites.oraclecorp.com/websites/pub/oracleperformance/ ------------------------------------------------------------- ----- Original Message ----- From: "Ramakrishna Menon" <[EMAIL PROTECTED]> To: "Log4J Users List" <[EMAIL PROTECTED]> Sent: Wednesday, June 23, 2004 9:12 AM Subject: Re: Fw: ThreadLocalAppender for log4j?resending > Hi Paul > I was supposed to work on this thread and get back to this list but > was caught up in other priorities at work. > I am now trying to redo some of the investigations I did earlier and also > look at > adapting your solution. Thought I would summarize what I am thinking of > doing (my understanding of log4j is fairly limited - I just know how to > get a simple logger up and running with a simple config file:-)) > > To recall the original issue, it was to log a message on the rendered url. > Now in our application we are using log4j to log messages already. I want > to intercept these messages and render them in a url based on a flag > that is set on the url (or in the session.) Important thing is that a url > should get messages only from the request (or thread) that was handled > while its rendering.) > > Now what I am thinking of doing is to > 1. create a class which is an appender that intercepts the messsages and > writes it to a > StringWriter with which it is initialized. > 2. at the beginning of the routine that handles a request, I create a new > appender and initialize it > with the stringwriter. It appends to the stringwriter any messages that it > gets. > > 3. at the end of the routine request handling routine, I get the > stringwriter from the appender and > destroy it in a finally clause. > > 4. In the logging properties file I would add this appender as well ( I am > not sure if this is necessary > since I create this appender manually ?) > > Does that sound right/sane/insane? > > Any other comments/thoughts. btw, I remember thinking about using > ThreadLocal but dont see it relevant > here now - not sure I am missing something I thought earlier :) > > Best Regards, > Menon:) > ------------------------------------------------------------- > Ramakrishna M. Menon (A Rafi Fan - http://www.mohdrafi.com ) > MBA, Berkeley > Oracle Corp.-> (650) 506-2343 > http://websites.oraclecorp.com/websites/pub/oracleperformance/ > ------------------------------------------------------------- > > ----- Original Message ----- > From: "Paul Smith" <[EMAIL PROTECTED]> > To: "Log4J Users List" <[EMAIL PROTECTED]> > Sent: Tuesday, March 02, 2004 2:22 PM > Subject: Re: Fw: ThreadLocalAppender for log4j? resending > > > > Ok, to get some context to what we did, our App had a MessageListener > > interface that was used a lot as a Listener callback to pass > > Informational messages to our GUI (I've put notes in []): > > > > public interface MessageListener extends EventListener { > > /** > > * This listener receives a notification > > */ > > public void receiveMessage(MessageEvent message); > > } > > > > [MessageEvent is a trivial class, MessageType=ERROR|INFO|WARN etc, plus > > a String message, I won't paste it here] > > > > //----- > > > > [Now we needed to adapt this interface to an Appender, here's the > > appender with the Thread specific filter. Note: > > convertLog4JToMessageEvent just converts LoggingEvent to MessageEvent] > > > > //----- > > .... > > public static final Appender > > createLog4JAppenderAdpater(MessageListener listener) > > { > > return Log4jAppender.create(listener); > > } > > > > private static final class Log4jAppender extends AppenderSkeleton > > { > > private MessageListener listener; > > > > private Log4jAppender(){} > > public static Log4jAppender create(MessageListener listener) > > { > > Log4jAppender appender = new Log4jAppender(); > > > > appender.listener = listener; > > > > final Thread threadThatCreatedTheAppender = > > Thread.currentThread(); > > > > appender.addFilter(new Filter(){ > > public int decide(LoggingEvent event) > > { > > if (Thread.currentThread() == threadThatCreatedTheAppender) > > { > > return Filter.ACCEPT; > > } > > return Filter.DENY; > > } > > }); > > return appender; > > } > > > > protected void append(LoggingEvent event) > > { > > listener.receiveMessage(convertLog4JToMessageEvent(event)); > > } > > > > public void close() > > { > > listener = null; > > } > > > > public boolean requiresLayout() > > { > > return false; > > } > > } > > > > // ------------- > > > > [Now, at the point of code where you can use this:] > > > > .... > > Logger loggerWeAreInterestedIn = > > Logger.getLogger(ClassWayDownHierachy.class); > > > > Appender appender = > > MessageListenerUtils.createLog4JAppenderAdpater(messageListener); > > > > loggerWeAreInterestedIn.addAppender(appender); > > > > try{ > > someObject.doSomeMethod(); > > }finally{ > > loggerWeAreInterestedIn.removeAppender(appender); > > } > > > > It's very important to remove the appender in the finally block > > otherwise you will be adding lots of appenders over time and will leak > > memory. There is probably a performance hit in doing all this, but > > sometimes that's better than the alternatives. It's not clean, but it > > does work. You might want to do something different than adapt the > > LoggingEvent to another class, but hopefully you can see the pattern. > > > > Hope this helps someone, or is food for further discussion. > > > > regards, > > > > Paul Smith > > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: [EMAIL PROTECTED] > > For additional commands, e-mail: [EMAIL PROTECTED] > > > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
