Load a properties files and use one of its properties to initialize log4j DOMConfigurator

In sample code below, we assume the main application configuration (properties) file is /opt/system.properties and it contains property LOG4J_XML_PATH which holds the full path to log4j xml configuration file. Of course, the configuration file can all other parameters required by the application.

public class ConfigFileReader{ 

    private static Properties systemProperties; 
    static {

        try {

            systemProperties = new Properties();

            systemProperties.load(new FileInputStream("/opt/system.properties"));

            String log4jpath=systemProperties.getProperty("LOG4J_XML_PATH");

            DOMConfigurator.configure(log4jpath);

       } catch (Exception e) {

              e.printStackTrace();

              System.exit(1);

       }
    }

}