An example application for my book The Java 9 Module System. The Service Monitor is an application that observes a hypothetical network of microservices by

• contacting individual services
• collecting and aggregating diagnostic data into statistics
• persisting statistics
• making statistics available via REST

It is split into a number of modules that focus on specific concerns. Each module has its own directory that contains the known folder structure, e.g. src/main/java.

The master branch uses basic features, except where it has to use automatic and unnamed modules for the non-modularized dependencies (Spark, Hibernate). Other branches explore individual features of the module system:

• services aka provides ... with and uses
• implied readability aka requires transitive
• optional dependencies aka requires static
• qualified exports aka exports to

Then there are some branches that explore how things can break:

• duplicate modules (not properly documented)
• split package, on compilation and launch (not properly documented)
• missing transitive dependency (not properly documented)

This demo was developed against build 158 of the Jigsaw early access prototype. For it to work the Java 9 variants of javac, jar, and java must be available on the command line via javac9, jar9, and java9, e.g. by symlinking them.

The root directory contains a number of shell scripts:

• compile.sh: compiles the modules one by one
• multi-compile.sh: compiles all modules at once
• dry-run: launches the application with --dry-run, which aborts before calling the main method
• run: launches the application

To reduce setup efforts for IntelliJ users, I decided to leave my .idea folder in here. Let's see whether it helps...