private static ServiceLoader<SLF4JServiceProvider> getServiceLoader(final ClassLoader classLoaderOfLoggerFactory) {
        ServiceLoader<SLF4JServiceProvider> serviceLoader;
        SecurityManager securityManager = System.getSecurityManager();
        if(securityManager == null) {
            serviceLoader = ServiceLoader.load(SLF4JServiceProvider.class, classLoaderOfLoggerFactory);
        } else {
            final PrivilegedAction<ServiceLoader<SLF4JServiceProvider>> action = () -> ServiceLoader.load(SLF4JServiceProvider.class, classLoaderOfLoggerFactory);
            serviceLoader = AccessController.doPrivileged(action);
        }
        return serviceLoader;
    }
System property for explicitly setting the provider class. If set and the provider could be instantiated,
then the service loading mechanism will be bypassed.

@since 2.0.9
slf4j-api/src/main/java/org/slf4j/LoggerFactory.java