Question

We are building a small application using different architectural layers such as domain, interface, infrastructure and application. This follows the Onion DDD model. Now I am wondering if there is any benefit in splitting the application into a multimodule maven project. As far as I can see now it seems to make things more difficult than needed. The entire application will be deployed as a single WAR file into a Tomcat container.

Answer 1

Splitting your application makes sense for the following:

• When a certain part of the project needs to have new functionality or bug fixes, you can simply focus on that module and run just the tests for it. Compiling a fraction of all the code and running just the related tests speeds up your work.

• You can re-use the code from the modules across different projects. Let’s assume your project contains some well-written generic-enough code for mail sending. If you later have another project that need mail sending functionality, you can simply re-use your existing module or build upon it (in another module by adding it as a dependency).

• Easier maintainability on the long run. Maybe now it seems like a small project. In a few months things might look different and then you’ll need to do more refactoring to split things into logical units (modules).

• Conceptual clarity (as added by Adriaan Koster).

Concerning the WAR: You can have an assembly module which puts things together and produces a final WAR file from all the related modules.

Initially, this may seem as more work, but in the long-run, modularized projects are easier to work with and to maintain. Most sane developers would prefer this approach.