Question

I am using spring to inject a class into my PropertyDefiner implementation which will be used to help set up some properties within the logback.xml file (through dynamic property loading).

I’d love to get this class loaded and instantiated before logback is configured. Any thoughts on how to do this?

Answer 1

My solution resulted in not implementing a PropertyDefiner. The original question became an issue of not having the application context from spring to set the dynamic properties. I’m not sure why, but code in a later listener (after the Spring listeners) would get called (invoking the LoggerFactory call) before the application context was available. I tried a number of things, until I starting looking at a different approach.

Instead of using dynamic properties I created a listener (called on server startup) which then programmatically sets up my appender with the properties I want (through the createAdminNotifyAppender).

@Override
public void contextInitialized(ServletContextEvent arg0)
{
    //Set up the property reader to pull the correct properties
    ServletContext context = arg0.getServletContext();
    ApplicationContext appContext = WebApplicationContextUtils.getWebApplicationContext(context);
    propReader = (AppConfigPropertiesReader)appContext.getBean("propertySourcesPlaceholder");

    LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();

    createAdminNotifyAppender(lc, propReader);
}

The createAdminNotify method simply sets up an appender and adds it to the logging context. (if you’re really interested, you can see that method’s implementation on this thread).

Now I have a separate and modular listener that I can add to other apps that are using logback, but possibly with different properties. The properties are pulled from a database and can also vary by environment.