configure log4j to log to custom file at runtime

问题:

Can anyone please guide me as to how I can configure log4j to log to a specific file that I specify at run-time.The name and path of the log file are generated at run-time and the application must log to that particular file.

Generally file appender entries in the log4j.properties file points to the log file that will be used by the application.However in this case I would like to read the log file path from the command line and log to that particular file.

How can I achieve this ?

回答1:

Adapted from the log4j documentation:

import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.apache.log4j.SimpleLayout;
import org.apache.log4j.FileAppender;

public class SimpandFile {
   static Logger logger = Logger.getLogger(SimpandFile.class);
   public static void main(String args[]) {

      // setting up a FileAppender dynamically...
      SimpleLayout layout = new SimpleLayout();    
      FileAppender appender = new FileAppender(layout,"your filename",false);    
      logger.addAppender(appender);

      logger.setLevel((Level) Level.DEBUG);

      logger.debug("Here is some DEBUG");
      logger.info("Here is some INFO");
      logger.warn("Here is some WARN");
      logger.error("Here is some ERROR");
      logger.fatal("Here is some FATAL");
   }
}

回答2:

You can also do this from the log4j.properties file. Using the sample file below I have added the system property ${logfile.name}:

# logfile is set to be a RollingFileAppender
log4j.appender.logfile=org.apache.log4j.RollingFileAppender
log4j.appender.logfile.File=${logfile.name}
log4j.appender.logfile.MaxFileSize=10MB
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=[%-5p]%d{yyyyMMdd@HH\:mm\:ss,SSS}\:%c - %m%n

The log file name can then be set two different ways:

1. As a command line, system property passed to java "-Dlogfile.name={logfile}"

2. In the java program directly by setting a system property (BEFORE you make any calls to log4j).

   System.setProperty("logfile.name","some path/logfile name string");

回答3:

Can be also done by this properties define in log4j.properties file

log4j.appender.logfile=org.apache.log4j.RollingFileAppender
log4j.appender.logfile.maxFileSize=5000KB
log4j.appender.logfile.maxBackupIndex=5
log4j.appender.logfile.File=/WebSphere/AppServer/profiles/Custom01/error.log
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} %5p [%t] %C %M %c{1}:%L - %m%n

回答4:

Working and same has been tested

// setting up a FileAppender dynamically...
SimpleLayout layout = new SimpleLayout(); 
RollingFileAppender appender = new RollingFileAppender(layout,"file-name_with_location",true);
                    appender.setMaxFileSize("20MB");
                    logger.addAppender(appender);