1. @aalmiray | andresalmiray.com
Building modular
applications with JPMS
and Layrry

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

3. @aalmiray | andresalmiray.com
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

4. @aalmiray | andresalmiray.com
However …

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

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

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

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

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

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

15. @aalmiray | andresalmiray.com
Hello Layrry!

16. Layrry
JPMS

17. Launch!

18. YAML sucks!

19. TOML rocks!

20. Plugin Architectures

21. 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 }

22. 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 }

23. Parameterization

25. layrry-launcher-1.0-SNAPSHOT-all.jar
—layers-config javafx.toml
—properties versions.properties

26. @aalmiray | andresalmiray.com
Launch options
• Use the ready made launcher from the command line.
• Build your custom launcher.
• Or …

27. jbang layrry@moditect
—layers-config javafx.toml
—properties versions.properties

28. DEMO

29. @aalmiray | andresalmiray.com
Future
• Support remote configuration (?)
• Ready made binary distributions
• Distribution channels
• Github releases
• Homebrew (?)
•

30. @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/
• https://github.com/moditect/layrry/
• https://github.com/moditect/layrry-examples/

32. @aalmiray | andresalmiray.com