Java – set an absolute path for a “log4j.properties” file

apache-commons-loggingjavalog4jlogging

I am using apache commons + log4j for my web app.

normally log4j needs a configuration file inside the classpath; but I need to delegate the logging configuration to an external file (I need to deploy a .war in an environment, but the log configurations (max size, position, etc) it's up to a second team.

I have a commons-logging.properties in my classpath

org.apache.commons.logging.Log=org.apache.commons.logging.impl.Log4JLogger
# log4j.configuration=/absolute/path/where/external/logs/are/log4j.properties

unfortunately, the commented line doesn't work.

Is there a way to set up log4j with an external configuration file?

Best Solution

You can set it as a system property log4j.configuration property .. for example in J2SE app

java -Dlog4j.configuration=file:/path/to/log4j.properties myApp

Note, that property value must be a URL.

For more read section 'Default Initialization Procedure' in Log4j manual.

It's also possible letting a ServletContextListener set the System properties:

import java.util.Enumeration;
import javax.servlet.*;

public class SystemPropertiesHelper implements
        javax.servlet.ServletContextListener {
    private ServletContext context = null;

    public void contextInitialized(ServletContextEvent event) {
        context = event.getServletContext();
        Enumeration<String> params = context.getInitParameterNames();

        while (params.hasMoreElements()) {
          String param = (String) params.nextElement();
          String value = 
            context.getInitParameter(param);
          if (param.startsWith("customPrefix.")) {
              System.setProperty(param, value);
          }
        }
    }

    public void contextDestroyed(ServletContextEvent event) {
    }
}

And then put this into your web.xml (should be possible for context.xml too)

<context-param>
        <param-name>customPrefix.property</param-name>
        <param-value>value</param-value>
        <param-type>java.lang.String</param-type>
</context-param>

<listener>
    <listener-class>servletUtils.SystemPropertiesHelper</listener-class>    
</listener>

I got this from this listener code from answer .

I hope this could help you!

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