Question

This is my Student class that used to test log4j.

public class Student{    
    private static final Logger logger = Logger.getLogger(Student.class.getName());   

    public Student() {  
         PropertyConfigurator.configure("log4j.properties");  
    }

    public static void main(String args[]){  
        logger.log(Level.INFO, "My log4j Test");    
    } 
}

This is my log4j.properties file

log4j.rootLogger=INFO,Appender1,Appender2
log4j.appender.Appender1=org.apache.log4j.ConsoleAppender
log4j.appender.Appender2=org.apache.log4j.RollingFileAppender
log4j.appender.Appender2.File=C:/Log4j/MyLogExample.log

log4j.appender.Appender1.layout=org.apache.log4j.PatternLayout`  
log4j.appender.Appender1.Target=System.out`   
log4j.appender.Appender1.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n`  

log4j.appender.Appender2.layout=org.apache.log4j.PatternLayout`  
log4j.appender.Appender2.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n`  

log4j.appender.Appender2.MaxFileSize=50KB`  
log4j.appender.Appender2.MaxBackupIndex=10` 

When I run this program using Eclipse MyLogExample.log file gets created. But after I have created a jar file and run it using the command prompt, the log file is not created.

in console i can see this error.

log4j:ERROR Could not read configuration file [log4j.properties]. 
java.io.FileNotFoundException: log4j.properties (The system cannot find the file specified) 

After I add the following code example, the log file is created even when the jar file run with command prompt.

PropertyConfigurator.configure("C:\\eclipeworkspace\\Log4jTest\\log4j.properties");

How I can give relative path instead of exact path?

Answer 1

log4j.properties should be in your classpath. Add it to the classpath when running from command line.

A better alternative is to specify the property file using

-Dlog4j.configuration=relative path/log4j.properties

from the command line.
In this case you can remove the line PropertyConfigurator.configure("log4j.properties"); from your code – you don’t need to do anything in the code to specify the property file.