Question

I’m currently working on a Java application which should have the capability to use different versions of a class at the same time (because of multi tenancy support). I was wondering, is there any good approach to manage this? My basic approach is to have an interface, lets say Car, and implement the different versions as CarV1, CarV2, and so on. Every version gets its own class.

My approach is kind of wiered, I think. But I didn’t found any literature regarding to this topic, but I actually don’t know what I should search for.

Answer 1

The interface idea is prudent. Combine it with a factory that can produce the required implementation instance depending on some external input, e. g. the tenant-id. If you don’t need to support multiple tenants in the same running instance of the application, you could also use something like the ServiceLocator from the JDK which allows to use a file-based configuration approach.

If you are running in an application server, consider just firing up multiple instances, each configured for a different client. The server will then take care of the separation of instances, just fine.

Otherwise, if you really think you need multiple implementations at the same time (at runtime) in a non-Java EE application, this is a tricky problem. Maybe you want to consider a look at OSGi containers, which provide features for having multiple versions of a class. However, an approach like this add significant complexity, if you are not already familiar with it.