Static class-dependant object initialization from child classes

Question

I have this parent abstract class which defines an Apache logger static object. Something like this:

import org.apache.log4j.Logger;

public abstract class A {

    private final static Logger logger;

        (...)

}

I know this code is illegal because the logger object is not initialized. The problem is I don't want to initialize it with logger = Logger.getLogger(A.class); because I want each child class to initialize it with its own class object, that way I will know which class caused which errors.

But at the same time I want to include some of my logging methods on the base class A.

What would be the best practice for this? Should I initialize it with A.class, then reinstantiate it for each child class? Somehow that feels incorrect to me.

Roman · Accepted Answer · 2012-07-18 15:39:24Z

2

Initialize it with the actual class it's created in:

logger = Logger.getLogger(getClass()); //log4j way of creating loggers

To do this you'll need to remove static modifier from your logger declaration. I prefer to keep it private and access it via a getter-method, but you can also make it protected and access directly from A subclasses.

You should not worry that many logger objects will be created, one logger per class instance: under the hood Logger contains a map of loggers, and every time you create a new logger - it's being cached. When you try to get logger for the same class the second time - it's just being retrieved from the inner map.

So, if you have 5 classes in your hierarchy - only 5 Logger objects will be created, no matter how many times you call getLogger(getClass()).

edited Jul 18, 2012 at 15:39

answered Jul 18, 2012 at 15:31

Roman

66.4k93 gold badges247 silver badges341 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

M Rajoy Over a year ago

I can't call getClass from a static scope. That's what my IDE says, anyway.

M Rajoy Over a year ago

Thanks, I will do that then. But this applies to this specific case of Apache logger, and I'm curious as to how would one solve this for any other static object. How would you solve it then?

Roman Over a year ago

I would create the same kind factory object (like Logger), and produce new instance of object every time it's called. If for whatever needs (performance/stateless objects/etc) at some point I decide, that I don't want to create new objects any more - I will introduce caching inside the factory-object.

hvgotcodes · Accepted Answer · 2012-07-18 15:31:34Z

0

Should I initialize it with A.class, then reinstantiate it for each child object?

You should reinstantiate it for each child class.

answered Jul 18, 2012 at 15:31

hvgotcodes

121k33 gold badges209 silver badges237 bronze badges

1 Comment

M Rajoy Over a year ago

sorry that's what I actually meant.

Collectives™ on Stack Overflow

Static class-dependant object initialization from child classes

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related