> For the complete documentation index, see [llms.txt](https://bernardo.gitbook.io/development-docs-java/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bernardo.gitbook.io/development-docs-java/logging-in-java/sl4j.md).

# SL4J

[Logging facade](https://www.slf4j.org/), which hides the actual logging library being used.

## Usage

```java
public class LoginHandler {

   private static final Logger LOGGER = LoggerFactory.getLogger(LoginHandler.class);

   public void login(String user) {
      LOGGER.debug("User {} logged in", user);
   }

}
```

## Logging Levels

Levels are defined by the Logger interface.

* Trace
* Debug
* Info
* Warn
* Error