How to dynamically manage project dependancies

Question

We are writing a new set of services and have decided to make them share a common interface... calling it a BaseService. The idea is that whenever anyone wants to develop a new service in our organization, they should be just able to extend and use this BaseService. We have written a few other classes which also form a part of this base jar, it does things like handle transactions and connect to database using hibernate etc.

Right now all the services that extend the BaseService are a part of the same project (Eclipse + Maven), and some of the services are dependent on each other, but because they are in the same project we don't have a problem with dependencies.However, we expect 40-50 services to be written which would extend base service and would also be interdependent. I am worried that the size of the base project would be huge and that just because when someone has to use one service they might have to depend on my base jar which has 50 services.

Is there a way that we can make some projects dynamically dependent on others? Lets say I have a service A which depends on service B, when I build/compile Service A,it should be able to realize that it has a dependency on service B and automatically use the Service B jar.

I have heard of OSGi, will it solve my problem or is there a way I can do it with Maven or is there a simpler solution ?

Sorry about the long post !

Thanks in advance for your suggestions

Answer 1

It doesn't make any sense to "dynamically" manage project dependencies, since build dependencies are by definition not dynamic.

Your question, at least for the moment, seems to be entirely about how to build your code rather than about how to run it. If you are interested in creating a runtime system in which new service implementations can be dynamically added then OSGi may be the solution to look at. An extra advantage here would be that you could enforce the separation of API from implementation, and prevent the implementing services from invalidly depending on parts of your core module that you do not want them to have visibility of.

You could also use OSGi to manage evolution of your core service API through versioning; for example how do you communicate the fact that a non-breaking change has been made to the API versus a breaking change etc.

Answer 2

I would say there are two options depending if i understand your question correct. First one. You have already defined an interface (java term) and now you have different implementations of that. The simple solution for Maven would be to a have a module which is called for example: service-api and than this will be released and can be used by others as dependencies. On their side they simply implement the interface. No problem with the dependencies. If you are more talking about OSGi than you should take a look to maven-tycho.