Use this to help avoid memory leaks. An EventBus always holds a strong reference to an event bus receiver class; a receiver class has one or more methods annotated with @Subscribe. A receiver class often has strong references to other classes. This easily creates memory leaks; consider the case where a GUI window listens to an EventBus. If the window closes, but has a registered event bus receiver, it is not garbage collected.

Using this artifact's annotations results in the creation of a WeakEventBus receiver that is used a a proxy to the strong receiver. The weak reciever only holds a weak reference to the strong receiver; so the strong receiver can be garbage collected. When the strong receiver is collected, the weak receiver is automatically unregistered.

The artifact requires jdk-11 or later.

Examine weak-event-bus-test's EventBusUser.java, and run it, for a complete example.

public static class SomeStrongBusReceiver {
    @WeakSubscribe
    public void catch1(SomeEvent ev) {
        // ...
    }
    @WeakSubscribe
    @WeakAllowConcurrentEvents
    public void catch2(SomeOtherEvent ev) {
        // ...
    }
}

eb = new SomeStrongBusReceiver; // If you might want to manually unregister.
WeakEventBus.register(eb, myEventBus);

In pom.xml

<dependency>
    <groupId>com.raelity.lib</groupId>
    <artifactId>weak-event-bus-receiver</artifactId>
    <version>1.0.0</version>
</dependency>

And in the maven-compiler-plugin's <configuration>

<annotationProcessors>
    <annotationProcessor>
        com.raelity.lib.eventbus.WeakEventBusProcessor
    </annotationProcessor>
</annotationProcessors>