...
import org.osgi.service.log.LogService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
...

public class MasterApplicationBootstrapImpl {
	...
	private LogService logger; // OSGi service
        ... 
	private static Logger logger2 = LoggerFactory.getLogger( MasterApplicationBootstrapImpl.class );
        ...
	@PostConstruct @Transactional
       	public synchronized void start() throws Exception {
                // [WORKS] Uses SLF4J API: the output is present on the log file
		logger2.info("Master Application Bootstrap starting ...");
                // [DOES NOT WORK] Uses OSGi service: nothing is written on the log file
		logger.log( LOG_INFO, "Master Application Bootstrap starting ..." );
                 ...
        }
        ...
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/osgi http://www.springframework.org/schema/osgi/spring-osgi.xsd"
	xmlns:osgi="http://www.springframework.org/schema/osgi">
        ...
	<osgi:reference id="logger" interface="org.osgi.service.log.LogService" />
        ...
</beans>