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Editorial Team
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Asked: 2026-06-08T03:54:40+00:00

In my current project I need to make a certain task create its own

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In my current project I need to make a certain task create its own logfile separate from what is configured in log4j.properties.

I try to achieve this by attaching a dynamically created FileAppender to the rootLogger:

public static void setupAnalysisLogfile(String filename) {
  PatternLayout layout 
           = new PatternLayout("%d{dd MMM yyyy HH:mm:ss,SSS} [%t] %-5p %C{1} %x - %m%n");
  if(Config.CREATE_SEPERATE_LOG)
  {
     FileAppender appender;
     try {
       String path = (Config.LOGFILE_PATH!=null)?Config.LOGFILE_PATH:filename;
       appender = new FileAppender(layout,path);
       appender.setName("Analysis Appender");
       org.apache.log4j.Logger.getLogger("my.package.hierarchy").addAppender(appender);
     } catch (IOException e) {
       org.apache.log4j.Logger.getLogger(Config.class).warn(
                                                      "Failed to create a dedicated log "
                                                      + filename, 
                                                      e);
     }
   }        
}

When Config.LOGFILE_PATH is not null (comes from a commandline parameter) everything works. The logfile is created in the specified path.

However, when LOGFILE_PATH is null no logfile is created, or rather nothing is ever written to it.

Running the program with -Dlog4j.debug gives:

log4j: setFile called: /home/tbender/.something/bytecode/OMFG_3527961e3fb1134e1d3221c000879a90ff1022b6/bytecode/OMFG-1340994475441.log, true
log4j: setFile ended

When I step through the code and keep an eye on the list of open filehandles, I can see that the filehandle is created during the creation of the appender. Once the application finishes no logfile exists.

Any ideas?

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1 Answer

  1. Editorial Team

    Okay in the end it was not FileAppend that caused to problem but a totally unrelated piece of code that deleted and recreated the folder where my logfile was residing. D’OH!

    Good tip for trouble like this: When you are in linux use strace:

    strace -tt -f -e trace=create,open,close,unlink -o strace.out java -jar yourjar.jar

    That will show you what files were created, oepened, closed or removed. You can also include a bunch of other stuff. More calls can be found here

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