Re: [logback-user] Setting log filename during runtime

14 Nov 2008

      Hello Jenny,

You can dynamically add properties for variable substitution to a logger 
context. Here is how:

  LoggerContext loggerContext = (LoggerContext)
          LoggerFactory.getILoggerFactory();
  JoranConfigurator jc = new JoranConfigurator();
  jc.setContext(loggerContext);
  loggerContext.reset();  // throw away default configuration

  // the next line is the whole point of the exercise
  loggerContext.putProperty("logFileName", valueObtainedFromLDAP);
  try {
    jc.doConfigure("path/to/a/configfile.xml");
  } catch (JoranException je) {
    je.printStackTrace();
  }
  StatusPrinter.printIfErrorsOccured(loggerContext);

And in configfile.xml mentioned above, you would have

<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
   <file>%{logFileName}</file>
   ...
</appender>

HTH,

Jenny wrote:
...
Hi Ceki,
Variable substition wouldn't accomplish what I want to achieve... or would it? :)
My goal is to set the log filename in a dynamic way - retrieve it from an LDAP configuration. I don't want it hardcoded in the logback.xml.
My understanding is that variable substition only works if the variable comes from an external properties file or set in system property.
thanks,
Jenny
--- On Thu, 11/13/08, Ceki Gulcu <listid@qos.ch> wrote:
...
From: Ceki Gulcu <listid@qos.ch>
Subject: Re: [logback-user] Setting log filename during runtime
To: "logback users list" <logback-user@qos.ch>
Date: Thursday, November 13, 2008, 4:11 PM
Hello Jenny,
Why are you setting the passing value of
"logFileName" MDC? Just set it as a 
variable, see http://logback.qos.ch/manual/joran.html and
search for "Variable 
substitution".
HTH,
Jenny wrote:
...
Hi, I'm not sure if this is the preferred way or
best practice... but what I did was extend the
RollingFileAppender and override the getFile() method.
and this getFile() method retrieves / generates the
log file name.
please let me know if you have better solutions.
thanks,
Jenny
=============================================
From: Jenny jenny_uy81@yahoo.com
Subject: Re: [logback-user] Setting log filename
during runtime
To: "logback users list" logback-user@qos.ch
Hello,
How can i set the log filename set during the init()
of my StartupServlet.
I tried using MDC but it's not working for me.
What happens is the file is not created. Instead a
file with name "%exp{logFileName}" \
is created on my web server's bin directory.
In my StartupServlet, I have this init method that
calls MDC.put().
public void init() throws ServletException {
MDC.put("logFileName",
"c:\\testlogs\\test.log");
Logger log =
LoggerFactory.getLogger(StartupServlet.class); 
log.info("This should be logged");
}
In my logback.xml, I have a MDC.get().
<appender name="FILE"
class="ch.qos.logback.core.rolling.RollingFileAppender">
<append>true</append>
<expression
name="logFileName">MDC.get("logFileName")</expression>
<file>%exp{logFileName}</file>
...
-- 
Ceki Gülcü
Logback: The reliable, generic, fast and flexible logging framework for Java.
http://logback.qos.ch