Skip to content

modularisation-cheatsheet.md

Latest commit

 

History

History
90 lines (71 loc) · 4.99 KB

modularisation-cheatsheet.md

File metadata and controls

90 lines (71 loc) · 4.99 KB

ServiceMonitor - Modularisation - Cheatsheet

Disclaimer: do not follow the steps below literally, in case of issues try to debug. If you think it is an issue, report back in the feedback form or ask on the IRC channel.

Enjoy the modularisation journey!

Modularisation steps (bottom-up migration)

  • Pre-modularisation detective work

      jdeps -s -R -cp 'monitor/target/libs/*' monitor/target/main-1.0-SNAPSHOT.jar

    jdeps tells us about the split package we encountered during the migration process

      jdeps -s -R -include 'monitor.*' -cp 'monitor/target/libs/*' monitor/target/Machine-1.0-SNAPSHOT.jar

    unnamed modules have a 'not found' against them - these are our modules that are not Java 9 modules yet

      jdeps -s -R -include 'monitor.*' --dot-output . -cp 'monitor/target/libs/*' monitor/target/Machine-1.0-SNAPSHOT.jar

    creates a dot output of the module graph

    Use the jdeps output to navigate through your module graph and learn about the dependencies between the modules.

  • Create modules

    • create monitor.utils

      • go to module in the IDE

        • In IntelliJ, Add the folder ... as a module via File > New > Module from Existing source (check search project recursively, and click on Next till you navigate till Finish, IntelliJ detects it to be a Java project)

      • Set the SDK and language level of the project and modules to Java 9

      • Go to monitor.utils > src/main/java, right mouse click > New > module-info.java, name the module monitor.utils

      • run ./compile.sh from the project root

      • run ./run.sh from the project root

      • put the jar onto the module-path in the compile.sh for monitor.utils

      • run ./compile.sh from the project root

      • we get errors:

          monitor.rest/src/main/java/monitor/rest/MonitorServer.java:16: error: package monitor.utils is not visible
  import static monitor.utils.Utils.toBase64;
                  ^

      • fix it by making the monitor.utils available in to monitor.rest during compile time (amend compile.sh for it, hint: --add-modules)

      • but also add it to monitor section in the compile.sh

      • run ./compile.sh from the project root

      • issue fixed

      • run ./run.sh from the project root

      • we get an error:

          Exception in thread "main" java.lang.NoClassDefFoundError: monitor/utils/Utils

      • add the newly created module to the run.sh

    • now make monitor.observer modular
      • create the module-info and make the respective package(s) available
      • then make monitor.observer.alpha, monitor.observer.beta modular
      • create the module-info for both and make the respective package(s) available, also define the dependency (check source to find out)
      • make the respective changes to the compile.sh (find out the modular dependencies)
      • resolve the compiler failures
      • run compile.sh again
      • make the respective changes to the run.sh (use the modular dependencies)
      • resolve the runtime failures
      • run run.sh again
    • now make monitor.statistics modular
      • create the module-info and make the respective package(s) available, also define the dependency (check source to find out)
      • make the respective changes to the compile.sh (find out the modular dependencies)
      • resolve the compiler failures
      • run compile.sh again
      • make the respective changes to the run.sh (use the modular dependencies)
      • resolve the runtime failures
      • run run.sh again
    • now make monitor.rest modular

      • create the module-info and make the respective package(s) available, also define the dependency (check source to find out)

      • define the dependencies on the automatic (unnamed) module

      • make the respective changes to the compile.sh (find out the modular dependencies)

      • resolve the compiler failures

      • you will need to make sure the automatic (unnamed) modules from the class path to the module path (amend compile.sh)

      • run compile.sh again

      • make the respective changes to the run.sh (use the modular dependencies)

      • resolve the runtime failures

      • run run.sh again

      • run curl http://localhost:4567/stats/xml

      • this should fail:

          javax.xml.bind.JAXBException: Package monitor.rest with JAXB class monitor.rest.StatisticsEntity defined in a module monitor.rest must be open to at least java.xml.bind module.

      • Amend the module-info to allow (opens) javax.xml.bind to reflectively see monitor.rest

      • run compile.sh again

      • run run.sh again

      • run curl http://localhost:4567/stats/xml

      • Continue modularising the remaining maven module(s)

If all of this does not make sense, watch the second half of Nicolai Parlog's video on From Jar hell and Back.