How to insert current webapp's folder name in log4j filename

Question

I'm writing a Java web application to deploy in Tomcat and i'm using log4j for logging. I like to insert automatically the web application's folder name in the generated log file's name.

Currently the filename setting looks like this in log4j.properties:

log4j.appender.R.File=${catalina.home}/logs/mywebapp.log

and i need something like this:

log4j.appender.R.File=${catalina.home}/logs/${current.webapp.folder}.log

Is there some kind of environment variable for this to specify in the properties file, or i have to instantiate the logger from code?

Answer 1

It's not a configuration file only solution, so i keep the question open for a while.

I've renamed the log4j.properties to myapp-log4j.properties and modified the log file name property like this:

log4j.appender.R.File=${catalina.base}/logs/#{context.name}.log

Because i have a servlet which is loaded at startup, i'm initializing log4j in the init() function.

String contextPath = getServletContext().getContextPath();

// First reconfigure log4j
String contextName = contextPath.substring(1);
if (!configureLog4J(contextName)) {
  return;
}

The function for this:

  public static final String LOG4JAPPENDERRFILE = "log4j.appender.R.File";

  private boolean configureLog4J(String contextName) {
    Properties props = new Properties();
    try {
       InputStream configStream = getClass().getResourceAsStream("/myapp-log4j.properties");
       props.load(configStream);
       configStream.close();
    } catch(IOException e) {
       System.out.println("FATAL! Cannot load log4j configuration file from classpath.");
       e.printStackTrace(System.out);
       return false;
    }

    String logFile = props.getProperty(LOG4JAPPENDERRFILE);
    logFile=logFile.replace("#{context.name}", contextName);
    props.setProperty(LOG4JAPPENDERRFILE, logFile);
    LogManager.resetConfiguration();
    PropertyConfigurator.configure(props);
    return true;
  }

It seems like to work fine, but i don't really like that i have to modify the properties file in code.