Coding to SOA, External Dependency

Question

This has happend to me more than once, thought someone can give some insight.

I have worked on multiple projects where my project depends on external service. When I have to run the application locally, i would need that service to be up. But sometimes I would be coding to the next version of their service which may not be ready.

So the question is, is there already a way that can have a mock service up and running that i could configure with some request and responses?

For example, lets say that I have a local application that needs to make a rest call to some other service outside to obtain some data. E.g, say, for given a user, i need to find all pending shipments which would come from other service. But I dont have access to that service.

In order to run my application, i need a working external service but I dont have access to it in my environment. Is there a better way rather than having to create a fake service?

Answer 1

One way is to create your own service which returns sample data in the same format as the external service - this is the mock service.

In this diagram, I have labelled the part of your application that connects to the service as the service client. Here, you just configure your application to point to your mock service while developing.

Another, possibly better, way - which I have used myself, I'll describe it here in general terms - is to have the service client implement an interface, through which the rest of your application accesses the service. Then you can just create another implementation of the interface which returns mock data:

With this system, you just change which implementation to use as needed, either through a configuration variable or build condition. Another advantage is that you can start coding the application without any reference to the soa technology used, it gives you flexibility while you wait for the service to be ready.