Generic way of getLogger from log4j.Logger

Question

Instead of specifying the class name on each class:

log = Logger.getLogger(Foo.class);
log = Logger.getLogger(Bar.class);
log = Logger.getLogger(Test.class);

Will it be OK to use :

log = Logger.getLogger(this.getClass());

What will be the implications?

Answer 1

If you create a subclass, the log messages will get logged to the subclass's logger.

package pkgone;
public class SuperType {
    private Logger log = Logger.getLogger(this.getClass());
    public void someAction() {
        log.info("Doing something");
    }
}

.

package pkgtwo;
import pkgone.SuperType;
public class SubType extends SuperType {
    // for instances of SubType, the log object in SuperType
    // will get initialized with SubType's class object
}

.

// some code somewhere that uses SubType
SubType obj = new SubType();
obj.someAction();

In the above example, "Doing something" will get logged to the pkgtwo.SubType logger instead of pkgone.SuperType logger, which may or may not be what you want.

Answer 2

Try this way to look up a generic class...

private static final Log LOGGER = Logger.getLogger(MethodHandles.lookup().lookupClass());

The best part is you can use this method statically.

Answer 3

If you don't want to repeat to make the logger and want to avoid write a wrong class name, there's @Log of Project Lombok.

If you don't mind using one more library in your project, you can simply add a logger with a simple annotation.

import lombok.extern.java.Log;
import lombok.extern.slf4j.Slf4j;

@Log
public class LogExample {    
  public static void main(String... args) {
    log.error("Something's wrong here");
  }
}