SLF4J 2 + Logback 1.4 - No SLF4J providers were found.

[albertus82]

Hi,

I'm migrating a Spring (non boot) web app from SLF4J 1.7 to 2.0, with Hibernate dependencies, deployed on JBoss EAP 7.4.

I'm facing the following issue: a Hibernate class gets a Logger early in the initialization phase of the web app; in that phase, ServiceLoader.load(SLF4JServiceProvider.class) returns nothing:

Thread [MSC service thread 1-8] (Suspended (breakpoint at line 103 in LoggerFactory))	
	owns: Class<T> (org.slf4j.LoggerFactory) (id=280)	
	owns: DeploymentUnitPhaseService<T>  (id=296)	
	LoggerFactory.findServiceProviders() line: 103	
	LoggerFactory.bind() line: 147	
	LoggerFactory.performInitialization() line: 139	
	LoggerFactory.getProvider() line: 422	
	LoggerFactory.getILoggerFactory() line: 408	
	LoggerFactory.getLogger(String) line: 357	
	Slf4jLoggerProvider.getLogger(String) line: 32	
	LoggerProviders.logProvider(LoggerProvider, String) line: 150	
	LoggerProviders.trySlf4j(String) line: 112	
	LoggerProviders.findProvider() line: 53	
	LoggerProviders.find() line: 32	
	LoggerProviders.<clinit>() line: 29	
	Logger.getLogger(String) line: 2465	
	Logger.getLogger(Class<?>) line: 2490	
	HibernatePersistenceProvider.<clinit>() line: 38	
	NativeConstructorAccessorImpl.newInstance0(Constructor<?>, Object[]) line: not available [native method]	
	NativeConstructorAccessorImpl.newInstance(Object[]) line: 62	
	DelegatingConstructorAccessorImpl.newInstance(Object[]) line: 45	
	Constructor<T>.newInstance(Object...) line: 490	
	PersistenceProviderHandler.deploy(DeploymentPhaseContext, Platform) line: 75	
	PersistenceBeginInstallProcessor.deploy(DeploymentPhaseContext) line: 49	
	DeploymentUnitPhaseService<T>.start(StartContext) line: 182	
	ServiceControllerImpl$StartTask.startService(Service, StartContext) line: 1739	
	ServiceControllerImpl$StartTask.execute() line: 1701	
	ServiceControllerImpl$StartTask(ServiceControllerImpl$ControllerTask).run() line: 1559	
	ContextClassLoaderSavingRunnable.run() line: 35	
	EnhancedQueueExecutor.safeRun(Runnable) line: 1990	
	EnhancedQueueExecutor$ThreadBody.doRunTask(Runnable) line: 1486	
	EnhancedQueueExecutor$ThreadBody.run() line: 1377	
	ServiceContainerImpl$ServiceThread(Thread).run() line: 834	

I tried to add ServiceLoader.load(SLF4JServiceProvider.class).forEach(System.out::println) in a static block inside my WebApplicationInitializer class (my web app entry point), and surprisingly the result is ch.qos.logback.classic.spi.LogbackServiceProvider@4e690ba0.

So at this point, I tried to invoke LoggerFactory.reset() (by reflection... for trial only) and the logging mechanism started working perfectly.

Is this a known issue? Any idea?

Thank you a lot.

[ceki]

This may be related to #304

[albertus82]

Thanks @ceki, I'll look at #304. Anyway is there a proper way to force SLF4J to rescan for providers?

[albertus82]

Fixed in SLF4J 2.0.4. Thanks.