ServiceMonitor - Migration

An example application for my book The Java 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 subprojects that focus on specific concerns. Each project 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.

Branches

Each of the branches contains a different version of the project:

• master: starting point, Java 8
• migrated: compatible with Java 9 to 11
• modularized: partially modularized

Build and Execution

In the project's root folder:

• to build: mvn clean install
• to run: java -cp 'app/*' 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

Troubles

Here's what you're facing. (If you get stuck, check the guide.)

Migration to Java 9

• internal BASE64Encoder is gone ~> use Base64.getEncoder instead
• JAXB API is not present ~> add java.xml.bind
• Common annotations are not present ~> add java.xml.ws.annotations
• split package: javax.annotation between java.xml.ws.annotations and jsr-305 ~> patch java.xml.ws.annotations
• old version of Mockito causes warnings ~> update to newer version, e.g. 2.8.47
• application class loader is no longer a URLClassLoader ~> use system property java.class.path

Migration to Java 10

• even new version of Mockito may cause problems ~> update to yet newer version, e.g. 2.18.3
• ASM dependency of Maven compiler plugin may cuase problems ~> update to newer version, e.g. 6.1.1

Migrating to Java 11

• Java EE modules were removed ~> add third-party dependencies