Question

Assuming that all my classes in the hierarchy have only the default constructor,what are the issues of creating Log instance as follows ?

 public abstract class AbstractService {


    protected static Log log=null;


    public AbstractService(){
        log=LogFactory.getLog(this.getClass().getName());
    }

    public void foo(){      
        log.debug("base foo() : ");
    }

}


class ServiceA extends AbstractService {    

    public void foo(){
        super.foo();

        log.debug("Overloaded foo() in ServiceA");      
    }
}


class ServiceB extends AbstractService {
    public void foo(){
        super.foo();
        log.debug("Overloaded foo() in ServiceB");      

    }
} 

Answer 1

Given that the “log” field is static (i.e. associated with the AbstractService class), it shouldn’t be set from the constructor (which is associated with a specific instance of that class).

You either need to:

• make the “log” field non-static (probably what you intended, given that you are naming it using getClass().getName()), or
• initialise it within its declaration, e.g. protected static Log log=LogFactory.getLog(AbstractClass.class);