public interface Log {
public void debug(Object msg);
public void debug(Object msg, Throwable t);
public void error(Object msg);
public void error(Object msg, Throwable t);
public void fatal(Object msg);
public void fatal(Object msg, Throwable t);
public void info(Object msg);
public void info(Object msg, Throwable t);
public void trace(Object msg);
public void trace(Object msg, Throwable t);
public void warn(Object msg);
public void warn(Object msg, Throwable t);
public boolean isDebugEnabled();
public boolean isErrorEnabled();
public boolean isFatalEnabled();
public boolean isInfoEnabled();
public boolean isTraceEnabled();
public boolean isWarnEnabled();
}

class SampleController {
  def index() {
    log.info('In the index action...')
    // ...
  }
}

class SampleController {
  def index() {
    try {
      // do something that might throw an exception
    } catch (Exception e) {
      log.error ('some message goes here', e)
    }
  }
}