This content originally appeared on DEV Community and was authored by Minsun
For months, I initialized loggers at class level:
Logger logger = Logger.getLogger(CurrentClass.getName());
Then a coworker introduced me to @Slf4j, simplifying logging to just annotations and direct log.info/debug calls.
What is SLF4J?
Simple Logging Facade for Java implements the Facade pattern - providing a unified interface to complex subsystems, like a building's facade concealing internal complexity.
Example usage:
@Slf4j
public class MyService {
public void doSomething() {
log.info("Hello, SLF4J!");
}
}
Why SLF4J?
Multiple logging options exist:
1.Log4j:
import org.apache.log4j.Logger;
private static final Logger logger = Logger.getLogger(MyClass.class);
2.java.util.logging:
import java.util.logging.Logger;
private static final Logger logger = Logger.getLogger(MyClass.class.getName());
3.Logback:
import ch.qos.logback.classic.Logger;
import org.slf4j.LoggerFactory;
private static final Logger logger = (Logger) LoggerFactory.getLogger(MyClass.class);
SLF4J requires only dependency changes, not code modifications, reducing coupling between application and logging implementations.
How SLF4J Works
SLF4J scans classpath for StaticLoggerBinder:
private static void bind() {
try {
Class.forName("org.slf4j.impl.StaticLoggerBinder");
} catch (ClassNotFoundException e) {
throw new NoClassDefFoundError("No logging implementation found");
}
}
Binds implementation:
public class StaticLoggerBinder implements LoggerFactoryBinder {
private static final StaticLoggerBinder SINGLETON = new StaticLoggerBinder();
private LoggerFactory loggerFactory;
private StaticLoggerBinder() {
loggerFactory = new LogbackLoggerFactory();
}
}
Service Locator Pattern Connection
While studying IoC alternatives to DI, I noticed similarities with the Service Locator pattern:
// Service Locator
public class ServiceLocator {
private static Map<String, Service> services = new HashMap<>();
public static Service getService(String name) {
return services.get(name);
}
}
// SLF4J's Similar Approach
public class LoggerFactory {
public static Logger getLogger(Class<?> clazz) {
return findPlatformLoggerBinder().getLogger(clazz);
}
}
SLF4J combines both patterns:
- Facade: Simplifies logging interface
- Service Locator: Dynamically binds implementations
This dual-pattern approach enables flexible runtime binding while maintaining clean interfaces.
This content originally appeared on DEV Community and was authored by Minsun
Minsun | Sciencx (2025-01-26T02:37:42+00:00) @Slf4j = Facade Pattern + Service Locator Pattern. Retrieved from https://www.scien.cx/2025/01/26/slf4j-facade-pattern-service-locator-pattern/
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