如何在Java中设计和接口（OOP类型），以便我可以使用直接数据库访问或使用Web服务？

Question

At the moment I have to query database that I do not own which has a web service, so what they provide is what I get. Since this is in house (sort of), I might be able to get direct access in the future so that I can get better data in my query.

I don't want to have to write everything again and again. If I did this in Java would I write an Interface (programming kind, think Implements Interface, OOP)? How would I do this? Or do I just write a whole new class and "plug it in."

This is just a regular client/server architecture. Http request, server calls the servlet or jsp, returns data.

I'm not sure if my idea is correct design or not.

Answer 1

Definitely sounds like you should use an interface with different implementations here. Something like:

public interface DataAccess {
    Data getData();
}

Then you can code against this API and just plugin/inject a different implementation as needed. So you could have this:

public class DirectDataAccess implements DataAccess {
    public Data getData() {
        //use JDBC, ORM, or similar
    }
}

Or this:

public class WebServiceDataAccess implements DataAccess {
    public Data getData() {
        //call web service
    }
}

But as long as your client code only references the DataAccess interface, then you have successfully decoupled your client from your service.