Show HN: PF4J-Plus – ServiceRegistry and EventBus for PF4J Plugin Systems

1 comments

• decebals 2 hours ago
  I'm the creator of PF4J (https://github.com/pf4j/pf4j) - a plugin framework for adding extensibility to Java applications, used by companies worldwide (https://github.com/pf4j/pf4j#trusted-by).

  After years of GitHub discussions, I kept seeing three recurring patterns everyone rebuilds:

  1. Service injection - custom PluginFactory boilerplate to wire platform services (Issue #319 is typical: https://github.com/pf4j/pf4j/issues/319)

  2. Plugin communication - everyone builds their own EventBus

  3. Configuration - no standard approach for plugin-scoped settings

  Hit these myself building a JavaFX app. PF4J handled loading, but then 30+ lines of factory code just to inject services.

  Built pf4j-plus to standardize this layer:

  BEFORE - custom factory everywhere:

      public class MyPluginFactory extends DefaultPluginFactory {
          @Override
          public Plugin create(PluginWrapper wrapper) {
              Plugin plugin = super.create(wrapper);
              if (plugin instanceof MyPlugin) {
                  ((MyPlugin) plugin).setGreetingService(App.getGreetingService());
                  ((MyPlugin) plugin).setEventBus(App.getEventBus());
              }
              return plugin;
          }
      }
  

  AFTER - declare once:

      PluginManager pm = PlusPluginManagerBuilder.create()
          .serviceRegistry(r -> {
              r.register(GreetingService.class, new DefaultGreetingService());
              r.register(EventBus.class, new DefaultEventBus());
          })
          .build();
  

  Plugins get ServiceRegistryAware, extensions use @Inject.

  What it provides:

  - ServiceRegistry - shared services for plugins

  - EventBus - decoupled communication

  - ConfigService - plugin-scoped configuration

  Not a DI container replacement. Just standardizes the platform layer you'd build anyway. Especially useful outside Spring (desktop apps, CLI tools, embedded systems).

  Early stage - using it in my own projects. Looking for feedback on what platform services are missing.

  Repo: https://github.com/pf4j/pf4j-plus

  Blog post: https://dev.to/decebals/why-i-built-pf4j-plus-1hl1