How to Use SLF4J with Java 9 Modules?

How do I effectively use SLF4J for logging in Java 9 modules?

SLF4J (Simple Logging Facade for Java) provides a simple and flexible API for logging, which can be easily integrated with Java 9 modules. This article outlines how to configure SLF4J with Java 9 module systems, ensuring modularity and effective logging.

module my.module {
    requires slf4j.api;
    requires ch.qos.logback.classic;
    exports my.package;
} 

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class MyClass {
    private static final Logger logger = LoggerFactory.getLogger(MyClass.class);

    public void doSomething() {
        logger.info("This is an info message");
    }
}

Causes

• The need to manage logging for modular applications.
• Compatibility issues with prior logging frameworks when transitioning to Java 9.

Solutions

• Include SLF4J and the desired logging backend (like Logback or Log4j) in your module's dependencies in the module descriptor (module-info.java).
• Use the appropriate logging implementation compatible with SLF4J, as it acts merely as a facade.
• Ensure that your module exports the required packages for logging, especially if accessing the logger from other modules.

Mistake: Not including the SLF4J dependencies in the module descriptor.

Solution: Ensure to add the SLF4J API and the selected implementation as `requires` in `module-info.java`.

Mistake: Failing to configure logging implementation correctly.

Solution: Make sure the chosen backend for SLF4J is correctly integrated and configured in your module.