Logback - set log file name programmatically

Question

I am using logback, and I am trying to set the log file name programmatically within my Java program (similar to Setting Logback Appender path programmatically), and I tried to adapt that solution as follows:

In logback-test.xml:

<appender name="FILE" class="ch.qos.logback.core.FileAppender">   <file>log/${log_file_name}.log</file>   ... 

And then again in my Java program:

String logFileName = "" + System.currentTimeMillis(); // just for example System.setProperty("log_file_name", logFileName);  LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory(); ContextInitializer ci = new ContextInitializer(lc); lc.reset(); try {     // I prefer autoConfig() over JoranConfigurator.doConfigure() so I     // wouldn't need to find the file myself.     ci.autoConfig(); } catch (JoranException e) {     // StatusPrinter will try to log this     e.printStackTrace(); } StatusPrinter.printInCaseOfErrorsOrWarnings(lc); 

However the result is two logs, one full and named as I wanted, e.g., "1319041145343.log", and the other is empty and named "log_file_name_IS_UNDEFINED.log". How do I stop this other empty log file from being created?

Answer 1

I believe the following to be closer to what you want.

import ch.qos.logback.classic.Logger; import ch.qos.logback.classic.encoder.PatternLayoutEncoder; import ch.qos.logback.core.FileAppender; import ch.qos.logback.core.util.StatusPrinter; import org.slf4j.LoggerFactory; import ch.qos.logback.classic.LoggerContext;  public class Main {   public static void main(String[] args) {     LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();      FileAppender fileAppender = new FileAppender();     fileAppender.setContext(loggerContext);     fileAppender.setName("timestamp");     // set the file name     fileAppender.setFile("log/" + System.currentTimeMillis()+".log");      PatternLayoutEncoder encoder = new PatternLayoutEncoder();     encoder.setContext(loggerContext);     encoder.setPattern("%r %thread %level - %msg%n");     encoder.start();      fileAppender.setEncoder(encoder);     fileAppender.start();      // attach the rolling file appender to the logger of your choice     Logger logbackLogger = loggerContext.getLogger("Main");     logbackLogger.addAppender(fileAppender);      // OPTIONAL: print logback internal status messages     StatusPrinter.print(loggerContext);      // log something     logbackLogger.debug("hello");   } } 

If all you need is to add a timestamp of the log file name, logback already supports the timestamp element. Thus, you actually don't need any custom code at all.