import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.xml.DOMConfigurator;

@WebListener
public class AppContextListener implements ServletContextListener {

    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ServletContext ctx = servletContextEvent.getServletContext();
        //initialize DB Connection
        //..........................

        //initialize log4j
        String log4jConfig = ctx.getInitParameter("log4j-config");
        if(log4jConfig == null){
            System.err.println("No log4j-config init param, initializing log4j with BasicConfigurator");
            BasicConfigurator.configure();
        }else {
            String webAppPath = ctx.getRealPath("/");
            String log4jProp = webAppPath + log4jConfig;
            File log4jConfigFile = new File(log4jProp);
            if (log4jConfigFile.exists()) {
                System.out.println("Initializing log4j with: " + log4jProp);
                DOMConfigurator.configure(log4jProp);
            } else {
                System.err.println(log4jProp + " file not found, initializing log4j with BasicConfigurator");
                BasicConfigurator.configure();
            }
        }
        System.out.println("log4j configured properly");
    }
}