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04_ServiceMonitor_modularisation_to_java_9

README.md

ServiceMonitor - Modularisation

Thanks to Nicolai Parlog for letting us use his original migration example into this exercise, among many other good things, also author of the book Java 9 Module System.

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.

It was developed as a Java 8 application and now needs to be made compatible with Java 9 and then be modularized.

Build and Execution

In the project's root folder:

  • to build: mvn clean install

  • to run: java -cp 'monitor/target/libs/*':'monitor/target/main-1.0-SNAPSHOT.jar' monitor.Main

  • to contact REST endpoints:

    • curl http://localhost:4567/stats/json
    • curl http://localhost:4567/stats/json64 | base64 -d
    • curl http://localhost:4567/stats/xml

  • scripts have also been provided (try them out in the end when it works):

    • compile.sh
    • run.sh

Troubles

Modularization

  • unexpressed transitive dependencies:
    • monitor ~> monitor.statistics (for Statistics et al)
    • monitor.rest ~> jackson.core (for JsonProcessingException)

Cheatsheet

To help and give a bit more hints during the refactoring process refer to our modularisation cheatsheet.

Warning: but this might just take away all the fun learning.