Here is an example of how you can use the DefaultJoranConfigurator class from the logback.classic package:

import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.joran.DefaultJoranConfigurator;
import ch.qos.logback.core.joran.spi.JoranException;
import ch.qos.logback.core.util.StatusPrinter;
import org.slf4j.LoggerFactory;

public class MyClass {
  public static void main(String[] args) {
    // Get the logger context
    LoggerContext context = (LoggerContext) LoggerFactory.getILoggerFactory();

    // Load the configuration from a file
    try {
      DefaultJoranConfigurator configurator = new DefaultJoranConfigurator();
      configurator.setContext(context);
      context.reset();
      configurator.doConfigure("path/to/config.xml");
    } catch (JoranException je) {
      // StatusPrinter will handle this
    }

    // Print logback's internal status
    StatusPrinter.printInCaseOfErrorsOrWarnings(context);
  }
}

The DefaultJoranConfigurator class is a subclass of the JoranConfigurator class and is used to load a logback configuration from an XML file. In this example, we create an instance of DefaultJoranConfigurator and set the logger context using the setContext method. We then reset the context and call the doConfigure method, passing in the path to the configuration file as an argument.

The StatusPrinter class is then used to print logback's internal status, which can be helpful for debugging purposes.