The VCS project repository should only contain the sources that are produced and maintained by developers. Certainly, enterprise applications will have to be deployed as some kind of binary artifacts. Only these shippable binaries can be executed as runnable software. The binaries are ultimately the outcome of the development and build process.
In the Java world this means that the Java source code is compiled to portable bytecode and is usually packaged as Web Application Archive (WAR) or Java Archive (JAR), respectively. WAR or JAR files comprise all classes and files required to ship an application, framework dependency, or library. The Java Virtual Machine (JVM) finally executes the bytecode and together with that, our business functionality.
In enterprise projects the deployment artifacts, the WAR or JAR files, are either deployed to an application container or already ship the container themselves. The application container is needed, since beside their distilled business logic, enterprise applications will have to integrate additional concerns, such as application life cycle or communication in various forms. For example, a web application that implements certain logic but is not addressable over HTTP communication has little value. In Java Enterprise, the application container is responsible for providing this integration. The packaged application contains the distilled business logic and is deployed to a server, which takes care of the rest.
In recent years, more Linux container technologies such as Docker have emerged. This carries the ideas of shippable binaries even further. The binary then not only contains the packaged Java application, but all components required to run the application. This, for examples, includes an application server, the Java Virtual Machine, and required operating system binaries. We will discuss the topic of shipping and deploying enterprise applications, especially regarding container technology, in Chapter 4, Lightweight Java EE.
The binaries are produced as part of the software build process. It enables to reliably recreate all binaries from the repository's sources. Therefore, the binaries should not be kept under version control. The same is true for generated source code. In the past, for example, JAX-WS classes which are required for SOAP communication were usually generated from descriptor files. Generated source code is created during the build process and should also not be kept under version control. The idea is to keep only the distilled source code in the repository and no artifacts that can be derived from it.