I had this problem with an application we are developing as well. Prior to setting up the logging a number of initialization steps are performed which may result in loggin messages being generated. I didn't want to print these until I knew whether they should be printed and how they should be formatted. Here is some of my actual code with a bit of verbage. Let me know if you need or would like more info.
I created a custom Appender:
public class StoreAppender extends AppenderSkeleton {
...
...
...public void dumpEvents() {
// dump out the stored logging events
Iterator iter = logEvents.iterator();
while (iter.hasNext()) {
LoggingEvent event = (LoggingEvent) iter.next();
Logger logger = Logger.getLogger(event.getLoggerName());
if ( event.getLevel().isGreaterOrEqual(logger.getEffectiveLevel()) ) {
logger.callAppenders(event);
}
}
} // dumpEvents
}
In my main class I instantiated it and set up a basic configurator that used it. This was what is used until logging is set up.
private static StoreAppender tempAppender = new StoreAppender();
static {
// setup a basic logging configuration to be used until we can read
// the logger properties file
BasicConfigurator.configure(tempAppender);
}
Here I set up the logging and dump out the log messages. If the program exits before this point it is still possible to print out any log messages that have been saved in StoreAppender (which is handy).
/**
* Initializes the log4j logging system.
*/
private void setupLogging() {
logger.info("Reading logger configuration from " + Utils.getURLSpecification(loggerPropertiesURL));
LogManager.resetConfiguration();
PropertyConfigurator.configure(loggerPropertiesURL);// have to assume appenders were setup properly since there is no programmatic way to check
tempAppender.dumpEvents();
tempAppender.dispose();
tempAppender = null;
} // setupLogging
charlie
Ian Huynh wrote:
In normal usage of Log4J, this is a standard practice
Logger logger = Logger.getLogger("com.acme.someclass");
if (logger.isDebugEnabled()) {
logger.debug("This is my debug message" );
}
What if the Category (ie 'com.acme.someclass') isn't a static value but some dynamic value ? One typical example would be an application that needs to parse some request and within the request, there are some contextual information that defines the Category name ?
So prior to knowing whether the Category of a logger is debug or infor etc.., we still like to buffer some messages and then once the Category can be defined, the debug messages can be flushed out or throw away.
eg.
Get a 'Buffer' Logger instance
Get Request from Client
logDebug("Got request from Client. about to parse")
parsedRequest = ParseRequest()
logDebug("Request Parsed")
String contextInfo = Get from parsedRequest
Re-get the Log4j logger using contextInfo as category (ie newLogger= Logger.getLogger( contextInfo ) )
if ( newLogger is debug enabled) flush all the previous messages to the appender
I am curious if anyone has similar requirements or have implememented something similar. I've thought about writing a custom BufferLogger but would rather see what else is out there.
Thanks in advance.
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