Spring constructor injection of SLF4J logger - how to get injection target class?

Question

I\'m trying to use Spring to inject a SLF4J logger into a class like so:

@Component
public class Example {

  private final Logger logger;

  @Autowired
  pu         


        

Answer 1

Yeah, you are going in the wrong direction. If I were you I would inject the LoggerFactory. If you want to hide that it is slf4j then I'd define a LoggerFactory interface and inject a class which delegates through to slf4j Logger.

public interface LoggerFactory {
    public Logger getLogger(Class<?> clazz);
}
...
import org.slf4j.LoggerFactory;
public class Slf4jLoggerFactory implements LoggerFactory {
    public Logger getLogger(Class<?> clazz) {
        return org.slf4j.LoggerFactory.getLogger(clazz);
    }
}

However, before you go there, this is approximately what org.apache.commons.logging is doing right? http://commons.apache.org/logging/

You use Log's instead of Loggers:

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
public class CLASS {
    private Log log = LogFactory.getLog(CLASS.class);
    ...

Apache then looks through the classpath to see if you have log4j or others and delegates to the "best" one that it finds. Slf4j replaces log4j in the classpath so if you have it loaded (and apache log4j excluded) commons logging will delegate to it instead.

Answer 2

To make your code more Spring aware use the InjectionPoint to define the loggers, i.e.:

@Bean
@Scope("prototype")
public Logger logger(InjectionPoint ip) {
    return Logger.getLogger(ip.getMember().getDeclaringClass());
}

@Scope("prototype") is needed here to create 'logger' bean instance every time method is called.