Logger Injection¶

Hermes provides the @InjectLogger annotation for zero-boilerplate logger injection using compile-time annotation processing.

Basic Usage¶

Annotate your class with @InjectLogger and extend the generated base class:

import io.hermes.InjectLogger;

@InjectLogger
public class UserService extends UserServiceHermesLogger {

    public void createUser(String username) {
        log.info("Creating user: {}", username);
    }
}

How It Works¶

The annotation processor generates a base class during compilation:

At compile time, the processor detects @InjectLogger
It generates <ClassName>HermesLogger with a protected Logger log field
Your class extends this base class and inherits the logger

Generated Code¶

For the example above, the processor generates:

public abstract class UserServiceHermesLogger {
    protected final Logger log = LoggerFactory.getLogger(UserService.class);
}

Benefits¶

Zero runtime reflection: Everything happens at compile time
GraalVM native-image compatible: No reflection metadata required
Type-safe: Compile-time errors if used incorrectly
Clean code: No boilerplate logger instantiation

Configuration¶

No configuration needed - the annotation processor runs automatically during Maven compilation via maven-compiler-plugin.

Viewing Generated Sources¶

Generated sources are located in:

target/generated-sources/annotations/

Alternative: Manual Logger Creation¶

If you prefer not to use annotation processing, create loggers manually:

import io.hermes.Logger;
import io.hermes.LoggerFactory;

public class UserService {
    private static final Logger log = LoggerFactory.getLogger(UserService.class);
}