I have an existing (Java desktop) application, which I'm looking at converting to use Inversion of Control principles. I'm just starting to look at the Java containers - HiveMind, Pico, Spring etc.
I'm not sure about how components/services/objects always have to be instantiated, rather than retrieved from an existing object.
In my application, I have a IHandler interface, a single instance of which is used by a number of objects. Currently, the instance is supplied by an Engine class, which has an inner class implementing IHandler, and a getHandler() method which returns an instance of the inner class.
I'm wondering how, when using Inversion of Control, I can supply this instance of IHandler to the objects which require it. Most of the containers seem to require that the instance is created. However, in this case, the instance should be returned from an existing object (which will also have been created by the container).
What's the best way to deal with this situation? I could, for example, make the IHandler inner class to be a public class, so it can be instantiated directly. But I'm not convinced that exposing the class in this way is the ideal way to do this.
Previous Topic
