Question

I have an in-house enterprise application (EJB2) that works with a certain BPM vendor. The current implementation of the in-house application involves pulling in an object that is only exposed by the vendor’s API and making changes to it through the exposed methods in the API.

I’m thinking that I need to somehow map an internal object to this external one, but that seems too simple and I’m not quite sure of the best strategy to go about doing this. Can anyone shed some light on how they have handled such a situation in the past?

I want to “black box” this vendor’s software so I can replace it easily if needed. What would be the best approach from a design point of view to somehow map an internal object to this exposed API object? Keep in mind that my in-house app needs to talk to the API still, so there is going to be some dependency between the two, but I want to reduce it so I can also test in isolation from this software using junit.

Thanks,
Jason

Answer 1

Create an interface for the service layer, internally all your code can work with that. Then make a class that uses that interface and calls the third party api methods and as the api facade.

i.e.

interface IAPIEndpoint {
    MyDomainDataEntity getData();
}

class MyAPIEndpoint : IAPIEndpoint {

    public MyDomainDataEntity getData() {
        MyDomainDataEntity dataEntity = new MyDomainDataEntity();
        // Call the third party api and fill it
        return dataEntity;
    }
}

It is always a good idea to interface out third party apis so you don’t get their funk invading your app domain, and you can swap out as needed. You could make another class implementation that uses a different service entirely.

To use it in code you just call

IAPIEndpoint endpoint = new MyAPIEndpoint(); // or get it specific to the lang you are using.

Making your stuff based on interfaces when it spans multiple implementations is the way to go. It works great for TDD as well so you can just swap out the interface to a local test one that can inspect your domain code entirely separate from the third party api.