Enthuware

Please confirm if I understand this concept correctly. In the real world, I would employ the top-down migration strategy because I don't have access to mysql-connector-java.jar The datalayer.jar may belong to the same company but another team could own that project.

That is correct.

What if I modularize only the myapp.jar and leave data-layer and mysql-connector-java on the classpath. Will it work?

No, classes in modules cannot access classes from jars on classpath. Only automatic modules can do that. So, you need to use automatic modules. Please go through a good book to understand this concept. We recommend the modules chapter of Deshmukh's 1z0815 fundamentals

Thanks for the info.

Does the question mean: how can you make myapp modularized with as few steps as possible, starting at the bottom? Would leaving mysql as it is, making datalayer automatic and myapp modularized be a good answer to that? Or is the premise of the question that mysql and datalayer should be modularized (either automatic or regular)?

The problem statement says that you have to use the bottom-up approach to modularize your app. If you use automatic modules then you are not using bottom-up approach (you are using top-down approach). The concept of automatic modules is created solely for the top-down approach.