code: private static synchronized void initializeLog4JSubSystem(String configFile)
      {
          LoggerFactory.getBootLogger().info("Initializing Log4J using file: '" + configFile + "'");
          if(configFile == null || "".equals(configFile.trim()))
          {
              // no configuration available
              LoggerFactory.getBootLogger().warn("No log4j configuration file specified");
          }
          else
          {
              // try resource look in classpath
              URL url = ClassHelper.getResource(configFile);
              LoggerFactory.getBootLogger().info("Initializing Log4J : resource from config file:" + url);
              if (url != null)
              {
                  PropertyConfigurator.configure(url);
              }
              // if file is not in classpath try ordinary filesystem lookup
              else
              {
                  PropertyConfigurator.configure(configFile);
              }
          }
          log4jConfigured = true;
      }
docs: Initialization of log4j <br>
  <b>NOTE</b>  - if log4j property file is called log4j.properties then
  log4j will be configured already.