Java 9 Modularity

Chapter 11. Build Tools and IDEs

In this book, we have been working with java and javac directly on a command line. This is not how most applications are built today. Most projects are built using tools such as Maven or Gradle. These build tools can take care of concerns such as managing the classpath during compilation, dependency management, and building artifacts such as JAR files. On top of that, most developers use an IDE such as Eclipse, IntelliJ IDEA, or NetBeans. IDEs make development easier by providing features such as code completion, error highlighting, refactoring, and code navigation.

Both build tools and IDEs need to know what types are available in a given context. Tools typically interact with the classpath to accomplish this. This significantly changes with the introduction of the Java module system. The classpath is no longer the (only) mechanism that controls which types are available. Tools now have to consider the module path as well. Moreover, there might be a mix of explicit modules, the classpath, and automatic modules. At the time of writing, the tool ecosystem is still working hard on Java 9 support. This chapter introduces some of the available tools, and discusses how they support the Java module system or likely will in the near future.

Apache Maven

Building a single module project with Maven is trivial. We will go over the steps to do this now, but we will not present the code or configuration. An example is included in the GitHub repository if ...