Inherit event handlers

When registering an event listener, Event Bus recursively walks the
entire inheritance tree and looks for event handlers.

core/src/test/java/dev/kske/eventbus/core/InheritanceTest.java

@@ -0,0 +1,40 @@
+package dev.kske.eventbus.core;
+
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests whether event handlers correctly work in the context of an inheritance hierarchy.
+ *
+ * @author Kai S. K. Engelbart
+ * @since 1.3.0
+ */
+class InheritanceTest extends SimpleEventListenerBase implements SimpleEventListenerInterface {
+
+	EventBus bus = new EventBus();
+
+	@Test
+	void test() {
+		bus.registerListener(this);
+		var event = new SimpleEvent();
+
+		bus.dispatch(event);
+		assertSame(4, event.getCounter());
+	}
+
+	@Override
+	void onSimpleEventAbstractHandler(SimpleEvent event) {
+		event.increment();
+	}
+
+	@Override
+	public void onSimpleEventInterfaceHandler(SimpleEvent event) {
+		event.increment();
+	}
+
+	@Event
+	private void onSimpleEventPrivate(SimpleEvent event) {
+		event.increment();
+	}
+}

core/src/test/java/dev/kske/eventbus/core/SimpleEvent.java

@@ -1,9 +1,31 @@
 package dev.kske.eventbus.core;
 
 /**
- * A simple event for testing purposes.
+ * A simple event for testing purposes. The event contains a counter that is supposed to be
+ * incremented when the event is processed by a handler. That way it is possible to test whether all
+ * handlers that were supposed to be invoked were in fact invoked.
  *
  * @author Kai S. K. Engelbart
  * @since 0.0.1
  */
-class SimpleEvent {}
+class SimpleEvent {
+
+	private int counter;
+
+	@Override
+	public String toString() {
+		return String.format("SimpleEvent[%d]", counter);
+	}
+
+	void increment() {
+		++counter;
+	}
+
+	int getCounter() {
+		return counter;
+	}
+
+	void reset() {
+		counter = 0;
+	}
+}

core/src/test/java/dev/kske/eventbus/core/SimpleEventListenerBase.java

@@ -0,0 +1,20 @@
+package dev.kske.eventbus.core;
+
+/**
+ * An abstract class defining a package-private and a private handler for {@link SimpleEvent}.
+ *
+ * @author Kai S. K. Engelbart
+ * @since 1.3.0
+ */
+abstract class SimpleEventListenerBase {
+
+	@Event
+	void onSimpleEventAbstractHandler(SimpleEvent event) {
+		event.increment();
+	}
+
+	@Event
+	private void onSimpleEventPrivate(SimpleEvent event) {
+		event.increment();
+	}
+}

core/src/test/java/dev/kske/eventbus/core/SimpleEventListenerInterface.java

@@ -0,0 +1,13 @@
+package dev.kske.eventbus.core;
+
+/**
+ * An interface defining a single handler for {@link SimpleEvent}.
+ *
+ * @author Kai S. K. Engelbart
+ * @since 1.3.0
+ */
+interface SimpleEventListenerInterface {
+
+	@Event
+	void onSimpleEventInterfaceHandler(SimpleEvent event);
+}