Build artifacts
Until now, our only tool for demarcating architecture boundaries within our code base was packages. All of our code has been part of the same monolithic build artifact.
A build artifact is the result of a (hopefully automated) build process. The most popular build tools in the Java world are currently Maven and Gradle. So, until now, imagine we had a single Maven or Gradle build script and we could call Maven or Gradle to compile, test, and package the code of our application into a single JAR file.
A main feature of build tools is dependency resolution. To transform a certain code base into a build artifact, a build tool first checks whether all the artifacts the code base depends on are available. If not, it tries to load them from an artifact repository. If this fails, the build will fail with an error before even trying to compile the code.
We can leverage this to enforce the dependencies (and thus enforce the boundaries) between the modules and layers...
