Building modular applications with the Java Platform Module System and Layrry

1. @aalmiray | andresalmiray.com
Building modular applications
with the Java Platform
Module System and Layrry

2. Happy 20th
Anniversary!

3. Andres
Almiray
Seasoned Sourceror
@ Oracle
Apache Groovy PMC
Java Champion
Hackergarten
github.com/aalmiray

4. @aalmiray | andresalmiray.com
JPMS

5. @aalmiray | andresalmiray.com
JPMS

6. @aalmiray | andresalmiray.com
Java Platform
Module System

7. @aalmiray | andresalmiray.com
Java Platform
Module System
• Also known by its project nickname: 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

8. However …

9. @aalmiray | andresalmiray.com
Some user statements
• It only allows for one version of a module
• It doesn’t allow adding modules at runtime
• I have to modularize ALL dependencies to reap the
benefits of the Java Platform Module System
• It’s so hard to map dependency coordinates to module
dependencies
• Help, non-exported packages of different modules collide!

12. @aalmiray | andresalmiray.com
What no one ever said
“Let’s use Module Layers to
tackle (some of) these issues”

13. https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/lang/ModuleLayer.html

14. @aalmiray | andresalmiray.com
Using the Layers API

16. !! Conflict !!

17. @aalmiray | andresalmiray.com
https://github.com/
moditect/layrry/

18. Gunnar
Morling
Open Source Software
Engineer
@ RedHat
Java Champion
Lead of Debezium
Bean Validation 2.0 Spec Lead
morling.dev

19. @aalmiray | andresalmiray.com
Hello Layrry!

20. Layrry
Java Platform
Module System

21. External Configuration

22. YAML sucks!

23. TOML rocks!

24. Parameterization

26. Launch!

28. $ java -jar layrry-launcher-1.0.0.Alpha1-all.jar
—layers-config javafx.toml
—properties versions.properties

29. $ sdk install layrry 1.0.0.Alpha1
$ layrry —layers-config javafx.toml
—properties versions.properties

30. $ sdk install jbang
$ jbang layrry@moditect
—layers-config javafx.toml
—properties versions.properties

31. Local Repositories

32. Local Repositories
• Artifacts can be organized in a local repository that does not require remote resolution
• Two layouts currently supported

33. Repository Layouts

34. Remote Layers

35. @aalmiray | andresalmiray.com
Remote Layers
• Layer configuration (and properties) files hosted at
remote locations.
• Mixing remote and local repositories is allowed.
• Supports dynamic plugins, plugin directories can only
be local.

36. Plugin Architectures

37. 1 package org.moditect.layrry.platform;
2
3 /**
4 * Implementations get notified about the
5 * addition or removal of plug-in layers.
6 * Retrieved via the service loader API.
7 */
8 public interface PluginLifecycleListener {
9
10 void pluginAdded(PluginDescriptor plugin);
11
12 void pluginRemoved(PluginDescriptor plugin);
13 }

38. 1 @Override
2 public void pluginAdded(PluginDescriptor plugin) {
3 ServiceLoader<MyService> services = ServiceLoader.load(
4 plugin.getModuleLayer(), MyService.class);
5
6 services.forEach(service -> {
7 // only process services declared by the added layer itself,
8 // but not from ancestor layers
9 if (service.getClass().getModule().getLayer() == layer) {
10 // process service ...
11 }
12 });
13 }

39. DEMO

40. Memory Leaks

45. Future

46. @aalmiray | andresalmiray.com
Future
• Binary distributions: Homebrew, Snap, Chocolatey, etc.
• Ability to create self-contained distributions
(e.g. jlink, Capsule)
• Derive layers from pom.xml?
• Programmatic plug-in API
• More JFR events for diagnostics
• Your contributions?!

47. @aalmiray | andresalmiray.com
Resources
• https://github.com/moditect/layrry/
• https://github.com/moditect/layrry-examples/

48. @aalmiray | andresalmiray.com
Resources
• 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/
• http://andresalmiray.com/layrry-1-0-0-alpha1-has-been-
released/

50. @aalmiray | andresalmiray.com