Question

I have a protocol stack implementation, where each layer receives the below layer in the constructor in order to communicate with them, like:

ApplicationLayer app = 
       new ApplicationLayer(
              new DataLinkLayer(
                     new PhysicalLayer()
));

What I need here it’s to control the classes of the instatiated objects, in order to to change the layers type just by changing a file (not a .java one, something like .xml). One of the possible usages it’s to implement logger layers between each layer, like:

ApplicationLayer app = 
           new ApplicationLayer( 
                  new AppLogLayer( 
                        new DataLinkLayer(
                              new DataLinkLogLayer(
                                    new PhysicalLayer()
))));

With that, my source code keeps the same in production (where we don’t need log) and in development (where I need logging), just by changing an external (to the .jar) file.

Is there any framework to do that? Preferentially with Eclipse integration.

Answer 1

Sounds like you want a dependency injection/inversion of control library. Spring and Guice are the canonical examples, although for something this simple you might just spin your own.