Plug-in Architectures With Layrry and the Java Module System (vJUG)

-- A joint talk with Andres Almiray at Virtual JUG --

The Java Module System lays the foundation for building modularized applications on the JVM. It doesn’t concern itself though with resolving module versions and obtaining modules from repositories.

This is where Layrry comes in: an API and launcher for modularized Java applications which takes a descriptor of the module layer(s) to assemble, fetches the modules and starts up the application.

Join us for this session and learn how to:

* Build Java applications using layers, e.g. providing isolation between different versions of one module.
* Use jbang to launch your layered apps in no time.
* Create plug-in based rich-client applications using JavaFX and Layrry, allowing to – dynamically reconfigure and update your layer hierarchy, no restarts required.
* Create your own customized Layrry launcher if needed

This session is code-centered, be ready to see the Java Module System, Layrry, and JavaFX in action!

Transcript

1. @gunnarmorling | @aalmiray #Layrry
   Plug-in Architectures With Layrry and
   the Java Module System
   Gunnar Morling | Andres Almiray
   

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2. @gunnarmorling | @aalmiray #Layrry
   Gunnar Morling
   ● Open source software engineer at Red Hat
   ○ Debezium
   ○ Hibernate
   ● Spec Lead for Bean Validation 2.0
   ● Java Champion
   ● @gunnarmorling
   

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3. @gunnarmorling | @aalmiray #Layrry
   Andres Almiray
   ● Senior Principal Product Manager @ Oracle
   ○ “Seasoned Sourceror”
   ● ❤ Open Source & Java
   ● Apache Groovy PMC
   ● Java Champion Alumni
   ● @aalmiray
   

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4. @gunnarmorling | @aalmiray #Layrry
   JPMS
   Java Platform Module System (also known as Jigsaw)
   Introduced in Java 9
   Designed to break down the JVM monolith
   Applicable to user space as well
   The promise is to give developers better code encapsulation and design foundations
   

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5. @gunnarmorling | @aalmiray #Layrry
   However...
   © Alexander Henning Drachmann https://flic.kr/p/uUA4G (CC BY-SA 2.0)
   

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6. @gunnarmorling | @aalmiray #Layrry
   Some User Statements
   “JPMS only allows for one version of a module”
   “JPMS doesn’t allow to add modules at runtime”
   “I have to modularize ALL my dependencies in order to benefit from JPMS”
   “It’s so hard to map dependency coordinates to module dependencies”
   “Help, non-exported packages of different modules collide!”
   
   

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7. @gunnarmorling | @aalmiray #Layrry
   What no one ever said
   “Let’s use JPMS Layers to tackle
   (some of) these issues”
   

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8. @gunnarmorling | @aalmiray #Layrry
   Module Layers
   https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/ModuleLayer.html
   

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9. @gunnarmorling | @aalmiray #Layrry
   Using the Layers API
   

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10. @gunnarmorling | @aalmiray #Layrry
    Hello, Layrry!
    An API and Launcher for Modularized Java Applications
    

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11. @gunnarmorling | @aalmiray #Layrry
    Hello,
    Layrry!
    

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12. @gunnarmorling | @aalmiray #Layrry
    Layrry
    JPMS
    © Christoper Michel https://flic.kr/p/UMtHv5 (CC BY 2.0)
    

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13. @gunnarmorling | @aalmiray #Layrry
    Ready-Made
    Launcher
    layrry-launcher--all.jar \
    —layers-config layers.yml
    

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14. @gunnarmorling | @aalmiray #Layrry
    Parameterization
    

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15. @gunnarmorling | @aalmiray #Layrry
    Built-in
    Template
    Support
    layrry-launcher--all.jar \
    —layers-config javafx.toml \
    —properties versions.properties
    

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16. @gunnarmorling | @aalmiray #Layrry
    jbang layrry@moditect \
    —layers-config javafx.toml \
    —properties versions.properties
    

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17. @gunnarmorling | @aalmiray #Layrry
    Local Repositories
    © Andres Almiray (CC BY 2.0)
    

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18. @gunnarmorling | @aalmiray #Layrry
    Local Repositories
    ● Artifacts can be organized in a local repository that does not require remote
    resolution
    ● Two layouts currently supported
    

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19. @gunnarmorling | @aalmiray #Layrry
    Local Repositories
    

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20. @gunnarmorling | @aalmiray #Layrry
    Local Repositories
    

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21. @gunnarmorling | @aalmiray #Layrry
    Plug-in Architectures
    © Justin Taylor https://flic.kr/p/4fQz9t (CC BY 2.0)
    

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22. @gunnarmorling | @aalmiray #Layrry
    Plug-in Architectures
    Can dynamically add (and remove) layers at runtime
    

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23. @gunnarmorling | @aalmiray #Layrry
    Plug-in Architectures
    

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24. @gunnarmorling | @aalmiray #Layrry
    © Bob Adams https://flic.kr/p/cYV7gq (CC BY-SA 2.0)
    Demo
    

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25. @gunnarmorling | @aalmiray #Layrry
    Bonus: Class Unloading
    ● Classes and layer class loader subject to GC after plug-in removal
    ● Dragons beware, class loader leaks can happen
    ○ Dangling references in remaining layers
    ○ Started threads
    ○ Shutdown hooks
    

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26. @gunnarmorling | @aalmiray #Layrry
    

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27. @gunnarmorling | @aalmiray #Layrry
    

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28. @gunnarmorling | @aalmiray #Layrry
    

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29. @gunnarmorling | @aalmiray #Layrry
    

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30. @gunnarmorling | @aalmiray #Layrry
    Outlook
    ● Remote layer files
    ● Binary distributions: Github Releases, Homebrew, SDKMan, etc.
    ● Integration with jlink
    ● Derive layers from pom.xml?
    ● Programmatic plug-in API
    ● Your contributions?!
    

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31. @gunnarmorling | @aalmiray #Layrry
    Resources
    Source code
    https://github.com/moditect/layrry
    https://github.com/moditect/layrry-examples
    

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32. @gunnarmorling | @aalmiray #Layrry
    Resources
    Blog posts
    https://www.morling.dev/blog/introducing-layrry-runner-and-api-for-
    modularized-java-applications/
    https://www.morling.dev/blog/plugin-architectures-with-layrry-and-
    the-java-module-system/
    https://www.morling.dev/blog/class-unloading-in-layered-java-applications/
    

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33. @gunnarmorling | @aalmiray #Layrry
    Q & A
    

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34. @gunnarmorling | @aalmiray #Layrry
    Demo
    

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35. @gunnarmorling | @aalmiray #Layrry
    JavaFX Demo
    

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