Merge pull request 'Handler Caching' (#37) from f/handler-caching into develop

Reviewed-on: https://git.kske.dev/zdm/event-bus/pulls/37
Reviewed-by: delvh <leon@kske.dev>

Jenkinsfile

@@ -0,0 +1,41 @@
+pipeline {
+	agent any
+
+	options {
+		ansiColor('xterm')
+	}
+
+	stages {
+		stage('Build') {
+			steps {
+				sh 'mvn -DskipTests clean package'
+			}
+		}
+		stage('Test') {
+			steps {
+				sh 'mvn test'
+			}
+			post {
+				always {
+					junit '*/target/surefire-reports/*.xml'
+					publishCoverage adapters: [jacocoAdapter(mergeToOneReport: true, path: '*/target/site/jacoco/jacoco.xml')]
+				}
+			}
+		}
+		stage('SonarQube Analysis') {
+			when {
+				branch 'develop'
+			}
+			steps {
+				withSonarQubeEnv('KSKE SonarQube') {
+					sh 'mvn sonar:sonar'
+				}
+			}
+		}
+	}
+	post {
+		success {
+			archiveArtifacts artifacts: '*/target/event-bus-*.jar'
+		}
+	}
+}

README.md

@@ -183,14 +183,37 @@ private void onDeadEvent(DeadEvent deadEvent) { ... }
 ### Detecting Exceptions Thrown by Event Handlers
 
 When an event handler throws an exception, an exception event is dispatched that wraps the original event.
-A exception handler is declared as follows:
+An exception handler is declared as follows:
 
 ```java
 private void onExceptionEvent(ExceptionEvent ExceptionEvent) { ... }
 ```
-
 Both system events reference the event bus that caused them and a warning is logged if they are unhandled.
 
+#### Yeeting Exceptions Out of an Event Handler
+
+In some cases, a warning about an `Exception` that was thrown in an event handler is not enough, stays unnoticed, or an exception should be catched explicitly.
+Event Bus explicitly dispatches no `ExceptionEvent` when an `ExceptionWrapper` exception is thrown and instead simply rethrows it.
+`ExceptionWrapper` is an unchecked exception that (as the name says) simply wraps an exception that caused it.
+This means the following is possible and results in a normal program exit:
+```java
+@Event(String.class)
+void onString() {
+	throw new ExceptionWrapper(new RuntimeException("I failed!"));
+}
+
+void helloStackTrace() {
+	EventBus.getInstance().registerListener(this);
+	try {
+		EventBus.getInstance().dispatch("A string!");
+		System.exit(-1);
+	} catch(ExceptionWrapper e) {
+		e.getCause().printStackTrace();
+		System.exit(0);
+	}
+}
+```
+
 ### What About Endless Recursion Caused By Dead Events and Exception Events?
 
 As one might imagine, an unhandled dead event would theoretically lead to an endless recursion.
@@ -198,6 +221,15 @@ The same applies when an exception event handler throws an exception.
 
 To avoid this, system events never cause system events and instead just issue a warning to the logger.
 
+## Inheritance
+
+When a superclass or an interface of an event listener defines event handlers, they will be detected and registered by Event Bus, even if they are `private`.
+If an event handler is overridden by the listener, the `@Event` annotation of the overridden method is automatically considered present on the overriding method.
+If the overridden method already contains an implementation in the superclass, the superclass implementation is ignored as expected.
+
+The `@Priority` and `@Polymorphic` annotations are inherited both on a class and on a method level.
+If the priority or polymorphism has to be redefined on an inherited handler, the `@Event` annotation has to be added explicitly.
+
 ## Debugging
 
 In more complex setups, taking a look at the event handler execution order can be helpful for debugging.

core/pom.xml

@@ -0,0 +1,66 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<artifactId>event-bus-core</artifactId>
+	<name>Event Bus Core</name>
+
+	<parent>
+		<groupId>dev.kske</groupId>
+		<artifactId>event-bus</artifactId>
+		<version>1.2.0</version>
+	</parent>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.junit.jupiter</groupId>
+			<artifactId>junit-jupiter-api</artifactId>
+			<version>5.8.1</version>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+	<build>
+
+		<!-- Disable resource folder -->
+		<resources />
+
+		<plugins>
+
+			<!-- Run unit tests -->
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<version>3.0.0-M5</version>
+				<configuration>
+					<argLine>
+						${argLine}
+						--add-opens dev.kske.eventbus.core/dev.kske.eventbus.core=ALL-UNNAMED
+						--add-opens dev.kske.eventbus.core/dev.kske.eventbus.core.handler=ALL-UNNAMED
+					</argLine>
+				</configuration>
+			</plugin>
+
+			<!-- Generate coverage report -->
+			<plugin>
+				<groupId>org.jacoco</groupId>
+				<artifactId>jacoco-maven-plugin</artifactId>
+				<version>0.8.7</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>prepare-agent</goal>
+						</goals>
+					</execution>
+					<execution>
+						<id>report</id>
+						<phase>test</phase>
+						<goals>
+							<goal>report</goal>
+						</goals>
+					</execution>
+				</executions>
+			</plugin>
+
+		</plugins>
+	</build>
+</project>

core/src/main/java/dev/kske/eventbus/core/Event.java

@@ -30,13 +30,5 @@ public @interface Event {
 	 * @return the event type accepted by the handler
 	 * @since 1.0.0
 	 */
-	Class<?> value() default USE_PARAMETER.class;
-
-	/**
-	 * Signifies that the event type the handler listens to is determined by the type of its only
-	 * parameter.
-	 *
-	 * @since 0.0.3
-	 */
-	static final class USE_PARAMETER {}
+	Class<?> value() default void.class;
 }

core/src/main/java/dev/kske/eventbus/core/EventBus.java

@@ -2,7 +2,8 @@ package dev.kske.eventbus.core;
 
 import java.lang.System.Logger;
 import java.lang.System.Logger.Level;
-import java.lang.reflect.InvocationTargetException;
+import java.lang.annotation.Annotation;
+import java.lang.reflect.*;
 import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Consumer;
@@ -14,9 +15,8 @@ import dev.kske.eventbus.core.handler.*;
  * <p>
  * A singleton instance of this class can be lazily created and acquired using the
  * {@link EventBus#getInstance()} method.
- * <p>
- * This is a thread-safe implementation.
  *
+ * @implNote This is a thread-safe implementation.
  * @author Kai S. K. Engelbart
  * @since 0.0.1
  * @see Event
@@ -90,6 +90,16 @@ public final class EventBus {
 	 */
 	private final Map<Class<?>, TreeSet<EventHandler>> bindings = new ConcurrentHashMap<>();
 
+	/**
+	 * A cache mapping an event class to all handlers the event should be dispatched to. This
+	 * includes polymorphic handlers that don't reference the event class explicitly. If an event
+	 * class is not contained inside this cache, the {@link #bindings} have to be traversed manually
+	 * in search of applicable handlers.
+	 *
+	 * @since 1.3.0
+	 */
+	private final Map<Class<?>, TreeSet<EventHandler>> bindingCache = new ConcurrentHashMap<>();
+
 	/**
 	 * Stores all registered event listeners (which declare event handlers) and prevents them from
 	 * being garbage collected.
@@ -112,10 +122,11 @@ public final class EventBus {
 	 *
 	 * @param event the event to dispatch
 	 * @throws EventBusException    if an event handler isn't accessible or has an invalid signature
+	 * @throws ExceptionWrapper     if it is thrown by an event handler
 	 * @throws NullPointerException if the specified event is {@code null}
 	 * @since 0.0.1
 	 */
-	public void dispatch(Object event) throws EventBusException {
+	public void dispatch(Object event) {
 		Objects.requireNonNull(event);
 		logger.log(Level.INFO, "Dispatching event {0}", event);
 
@@ -140,6 +151,10 @@ public final class EventBus {
 
 							// Transparently pass error to the caller
 							throw (Error) e.getCause();
+						else if (e.getCause() instanceof ExceptionWrapper)
+
+							// Transparently pass exception wrapper to the caller
+							throw (ExceptionWrapper) e.getCause();
 						else if (event instanceof DeadEvent || event instanceof ExceptionEvent)
 
 							// Warn about system event not being handled
@@ -170,11 +185,15 @@ public final class EventBus {
 	 * Searches for the event handlers bound to an event class. This includes polymorphic handlers
 	 * that are bound to a supertype of the event class.
 	 *
+	 * @implNote If the given event type was requested in the past, the handlers are retrieved from
+	 *           the {@link #bindingCache}. If not, the entire {@link #bindings} are traversed in
+	 *           search of polymorphic handlers compatible with the event type.
 	 * @param eventType the event type to use for the search
 	 * @return a navigable set containing the applicable handlers in descending order of priority
 	 * @since 1.2.0
 	 */
 	private NavigableSet<EventHandler> getHandlersFor(Class<?> eventType) {
+		return bindingCache.computeIfAbsent(eventType, k -> {
 
 			// Get handlers defined for the event class
 			TreeSet<EventHandler> handlers =
@@ -188,6 +207,7 @@ public final class EventBus {
 							handlers.add(handler);
 
 			return handlers;
+		});
 	}
 
 	/**
@@ -214,7 +234,7 @@ public final class EventBus {
 	 * @since 0.0.1
 	 * @see Event
 	 */
-	public void registerListener(Object listener) throws EventBusException {
+	public void registerListener(Object listener) {
 		Objects.requireNonNull(listener);
 		if (registeredListeners.contains(listener))
 			throw new EventBusException(listener + " already registered!");
@@ -232,7 +252,7 @@ public final class EventBus {
 			priority = listener.getClass().getAnnotation(Priority.class).value();
 
 		registeredListeners.add(listener);
-		for (var method : listener.getClass().getDeclaredMethods()) {
+		for (var method : getHandlerMethods(listener.getClass())) {
 			Event annotation = method.getAnnotation(Event.class);
 
 			// Skip methods without annotations
@@ -252,6 +272,49 @@ public final class EventBus {
 				listener.getClass().getName());
 	}
 
+	/**
+	 * Searches for event handling methods declared inside the inheritance hierarchy of an event
+	 * listener.
+	 *
+	 * @param listenerClass the class to inspect
+	 * @return all event handling methods defined for the given listener
+	 * @since 1.3.0
+	 */
+	private Set<Method> getHandlerMethods(Class<?> listenerClass) {
+
+		// Get methods declared by the listener
+		Set<Method> methods = getMethodsAnnotatedWith(listenerClass, Event.class);
+
+		// Recursively add superclass handlers
+		Class<?> superClass = listenerClass.getSuperclass();
+		if (superClass != null && superClass != Object.class)
+			methods.addAll(getHandlerMethods(superClass));
+
+		// Recursively add interface handlers
+		for (Class<?> iClass : listenerClass.getInterfaces())
+			methods.addAll(getHandlerMethods(iClass));
+
+		return methods;
+	}
+
+	/**
+	 * Searches for declared methods with a specific annotation inside a class.
+	 *
+	 * @param enclosingClass  the class to inspect
+	 * @param annotationClass the annotation to look for
+	 * @return all methods matching the search criteria
+	 * @since 1.3.0
+	 */
+	private Set<Method> getMethodsAnnotatedWith(Class<?> enclosingClass,
+		Class<? extends Annotation> annotationClass) {
+		var methods = new HashSet<Method>();
+		for (var method : enclosingClass.getDeclaredMethods())
+			if (method.isAnnotationPresent(annotationClass))
+				methods.add(method);
+
+		return methods;
+	}
+
 	/**
 	 * Registers a callback listener, which is a consumer that is invoked when an event occurs. The
 	 * listener is not polymorphic and has the {@link #DEFAULT_PRIORITY}.
@@ -321,15 +384,28 @@ public final class EventBus {
 	}
 
 	/**
-	 * Inserts a new handler into the {@link #bindings} map.
+	 * Inserts a new handler into the {@link #bindings} map. Additionally, the handler is placed
+	 * inside the {@link #bindingCache} where applicable.
 	 *
 	 * @param handler the handler to bind
 	 * @since 1.2.0
 	 */
 	private void bindHandler(EventHandler handler) {
-		bindings.putIfAbsent(handler.getEventType(), new TreeSet<>(byPriority));
+
+		// Bind handler
 		logger.log(Level.DEBUG, "Binding event handler {0}", handler);
-		bindings.get(handler.getEventType()).add(handler);
+		bindings.computeIfAbsent(handler.getEventType(), k -> new TreeSet<>(byPriority))
+			.add(handler);
+
+		// Insert handler into cache
+		bindingCache.computeIfAbsent(handler.getEventType(), k -> new TreeSet<>(byPriority))
+			.add(handler);
+
+		// Handler is polymorphic => insert where applicable
+		if (handler.isPolymorphic())
+			for (var binding : bindingCache.entrySet())
+				if (binding.getKey().isAssignableFrom(handler.getEventType()))
+					binding.getValue().add(handler);
 	}
 
 	/**
@@ -347,13 +423,25 @@ public final class EventBus {
 			var it = binding.iterator();
 			while (it.hasNext()) {
 				var handler = it.next();
-				if (handler.getListener() == listener) {
+				if (handler.getListener().equals(listener)) {
 					logger.log(Level.DEBUG, "Unbinding event handler {0}", handler);
 					it.remove();
 				}
 			}
 		}
 
+		// Remove bindings from cache
+		for (var binding : bindingCache.values()) {
+			var it = binding.iterator();
+			while (it.hasNext()) {
+				var handler = it.next();
+				if (handler.getListener().equals(listener)) {
+					logger.log(Level.TRACE, "Removing event handler {0} from cache", handler);
+					it.remove();
+				}
+			}
+		}
+
 		// Remove the listener itself
 		registeredListeners.remove(listener);
 	}
@@ -366,6 +454,7 @@ public final class EventBus {
 	public void clearListeners() {
 		logger.log(Level.INFO, "Clearing event listeners");
 		bindings.clear();
+		bindingCache.clear();
 		registeredListeners.clear();
 	}
 

core/src/main/java/dev/kske/eventbus/core/EventBusException.java

@@ -14,13 +14,14 @@ package dev.kske.eventbus.core;
  */
 public final class EventBusException extends RuntimeException {
 
-	private static final long serialVersionUID = 1L;
+	private static final long serialVersionUID = 7254445250300604449L;
 
 	/**
 	 * Creates a new event bus exception.
 	 *
 	 * @param message the message to display
 	 * @param cause   the cause of this exception
+	 * @since 0.0.1
 	 */
 	public EventBusException(String message, Throwable cause) {
 		super(message, cause);
@@ -30,6 +31,7 @@ public final class EventBusException extends RuntimeException {
 	 * Creates a new event bus exception.
 	 *
 	 * @param message the message to display
+	 * @since 0.0.1
 	 */
 	public EventBusException(String message) {
 		super(message);

core/src/main/java/dev/kske/eventbus/core/ExceptionWrapper.java

@@ -0,0 +1,24 @@
+package dev.kske.eventbus.core;
+
+/**
+ * This unchecked exception acts as a wrapper for an arbitrary exception to prevent an
+ * {@link ExceptionEvent} from being dispatched. Instead, the wrapped exception is rethrown by
+ * {@link EventBus#dispatch(Object)}.
+ *
+ * @author Kai S. K. Engelbart
+ * @since 1.2.1
+ */
+public final class ExceptionWrapper extends RuntimeException {
+
+	private static final long serialVersionUID = -2016681140617308788L;
+
+	/**
+	 * Creates a new exception wrapper.
+	 *
+	 * @param cause the exception to wrap
+	 * @since 1.2.1
+	 */
+	public ExceptionWrapper(Exception cause) {
+		super(cause);
+	}
+}

core/src/main/java/dev/kske/eventbus/core/Polymorphic.java

@@ -18,6 +18,7 @@ import java.lang.annotation.*;
  * @see Event
  */
 @Documented
+@Inherited
 @Retention(RUNTIME)
 @Target({ METHOD, TYPE })
 public @interface Polymorphic {

core/src/main/java/dev/kske/eventbus/core/Priority.java

@@ -21,6 +21,7 @@ import java.lang.annotation.*;
  * @see Event
  */
 @Documented
+@Inherited
 @Retention(RUNTIME)
 @Target({ METHOD, TYPE })
 public @interface Priority {

core/src/main/java/dev/kske/eventbus/core/handler/ReflectiveEventHandler.java

@@ -3,7 +3,6 @@ package dev.kske.eventbus.core.handler;
 import java.lang.reflect.*;
 
 import dev.kske.eventbus.core.*;
-import dev.kske.eventbus.core.Event.USE_PARAMETER;
 
 /**
  * An event handler wrapping a method annotated with {@link Event} and executing it using
@@ -37,7 +36,7 @@ public final class ReflectiveEventHandler implements EventHandler {
 		boolean defPolymorphism, int defPriority) throws EventBusException {
 		this.listener	= listener;
 		this.method		= method;
-		useParameter	= annotation.value() == USE_PARAMETER.class;
+		useParameter	= annotation.value() == void.class;
 
 		// Check handler signature
 		if (method.getParameterCount() == 0 && useParameter)
@@ -58,7 +57,8 @@ public final class ReflectiveEventHandler implements EventHandler {
 			? method.getAnnotation(Priority.class).value()
 			: defPriority;
 
-		// Allow access if the method is non-public
+		// Try to allow access if the method is not accessible
+		if (!method.canAccess(Modifier.isStatic(method.getModifiers()) ? null : listener))
 			method.setAccessible(true);
 	}
 

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

@@ -11,7 +11,7 @@ import org.junit.jupiter.api.*;
  * @author Leon Hofmeister
  * @since 0.1.0
  */
-public class CancelTest {
+class CancelTest {
 
 	EventBus	bus;
 	int			hits;
@@ -22,7 +22,7 @@ public class CancelTest {
 	 * @since 0.1.0
 	 */
 	@BeforeEach
-	public void registerListener() {
+	void registerListener() {
 		bus = new EventBus();
 		bus.registerListener(this);
 	}
@@ -34,7 +34,7 @@ public class CancelTest {
 	 * @since 0.1.0
 	 */
 	@Test
-	public void testCancellation() {
+	void testCancellation() {
 		bus.dispatch(new SimpleEvent());
 		assertEquals(1, hits);
 	}

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

@@ -10,7 +10,7 @@ import org.junit.jupiter.api.Test;
  * @author Kai S. K. Engelbart
  * @since 1.1.0
  */
-public class DeadTest {
+class DeadTest {
 
 	EventBus	bus		= new EventBus();
 	String		event	= "This event has no handler";
@@ -22,7 +22,7 @@ public class DeadTest {
 	 * @since 1.1.0
 	 */
 	@Test
-	public void testDeadEvent() {
+	void testDeadEvent() {
 		bus.registerListener(this);
 		bus.dispatch(event);
 		assertTrue(deadEventHandled);
@@ -36,7 +36,7 @@ public class DeadTest {
 	 * @since 1.1.0
 	 */
 	@Test
-	public void testUnhandledDeadEvent() {
+	void testUnhandledDeadEvent() {
 		bus.dispatch(event);
 	}
 

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

@@ -12,10 +12,9 @@ import org.junit.jupiter.api.*;
  */
 @Polymorphic
 @Priority(150)
-public class DispatchTest {
+class DispatchTest {
 
 	EventBus bus;
-	static int	hits;
 
 	/**
 	 * Constructs an event bus and registers this test instance as an event listener.
@@ -23,12 +22,12 @@ public class DispatchTest {
 	 * @since 0.0.1
 	 */
 	@BeforeEach
-	public void registerListener() {
+	void registerListener() {
 		bus = new EventBus();
 		bus.registerListener(this);
 		bus.registerListener(SimpleEvent.class, e -> {
-			++hits;
-			assertEquals(4, hits);
+			e.increment();
+			assertEquals(3, e.getCounter());
 		});
 	}
 
@@ -39,7 +38,7 @@ public class DispatchTest {
 	 * @since 0.0.1
 	 */
 	@Test
-	public void testDispatch() {
+	void testDispatch() {
 		bus.dispatch(new SimpleEventSub());
 		bus.dispatch(new SimpleEvent());
 	}
@@ -50,30 +49,40 @@ public class DispatchTest {
 	 * @since 1.2.0
 	 */
 	@Test
-	public void testDebugExecutionOrder() {
-		String executionOrder = bus.debugExecutionOrder(SimpleEvent.class);
-		System.out.println(executionOrder);
+	void testDebugExecutionOrder() {
 		assertEquals(
 			"Event handler execution order for class dev.kske.eventbus.core.SimpleEvent (3 handler(s)):\n"
 				+ "==========================================================================================\n"
-				+ "ReflectiveEventHandler[eventType=class dev.kske.eventbus.core.SimpleEvent, polymorphic=true, priority=200, method=void dev.kske.eventbus.core.DispatchTest.onSimpleEventFirst(), useParameter=false]\n"
-				+ "ReflectiveEventHandler[eventType=class dev.kske.eventbus.core.SimpleEvent, polymorphic=false, priority=150, method=static void dev.kske.eventbus.core.DispatchTest.onSimpleEventSecond(), useParameter=false]\n"
+				+ "ReflectiveEventHandler[eventType=class dev.kske.eventbus.core.SimpleEvent, polymorphic=true, priority=200, method=void dev.kske.eventbus.core.DispatchTest.onSimpleEventFirst(dev.kske.eventbus.core.SimpleEvent), useParameter=true]\n"
+				+ "ReflectiveEventHandler[eventType=class dev.kske.eventbus.core.SimpleEvent, polymorphic=false, priority=150, method=static void dev.kske.eventbus.core.DispatchTest.onSimpleEventSecond(dev.kske.eventbus.core.SimpleEvent), useParameter=true]\n"
 				+ "CallbackEventHandler[eventType=class dev.kske.eventbus.core.SimpleEvent, polymorphic=false, priority=100]\n"
 				+ "==========================================================================================",
-			executionOrder);
+			bus.debugExecutionOrder(SimpleEvent.class));
 	}
 
-	@Event(SimpleEvent.class)
+	/**
+	 * Tests whether the handlers bound to an event type are correct when retrieved from the binding
+	 * cache. On the second call of {@link EventBus#debugExecutionOrder(Class)} the cache is used.
+	 *
+	 * @since 1.3.0
+	 */
+	@Test
+	void testBindingCache() {
+		assertEquals(bus.debugExecutionOrder(SimpleEventSub.class),
+			bus.debugExecutionOrder(SimpleEventSub.class));
+	}
+
+	@Event
 	@Priority(200)
-	void onSimpleEventFirst() {
-		++hits;
-		assertTrue(hits == 1 || hits == 2);
+	void onSimpleEventFirst(SimpleEvent event) {
+		event.increment();
+		assertTrue(event.getCounter() == 1 || event.getCounter() == 2);
 	}
 
-	@Event(SimpleEvent.class)
+	@Event
 	@Polymorphic(false)
-	static void onSimpleEventSecond() {
-		++hits;
-		assertEquals(3, hits);
+	static void onSimpleEventSecond(SimpleEvent event) {
+		event.increment();
+		assertEquals(2, event.getCounter());
 	}
 }

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

@@ -10,7 +10,7 @@ import org.junit.jupiter.api.Test;
  * @author Kai S. K. Engelbart
  * @since 1.1.0
  */
-public class ExceptionTest {
+class ExceptionTest {
 
 	EventBus			bus			= new EventBus();
 	String				event		= "This event will cause an exception";
@@ -23,7 +23,7 @@ public class ExceptionTest {
 	 * @since 1.1.0
 	 */
 	@Test
-	public void testExceptionEvent() {
+	void testExceptionEvent() {
 		bus.registerListener(this);
 		bus.registerListener(new ExceptionListener());
 		bus.dispatch(event);
@@ -38,7 +38,7 @@ public class ExceptionTest {
 	 * @since 1.1.0
 	 */
 	@Test
-	public void testUnhandledExceptionEvent() {
+	void testUnhandledExceptionEvent() {
 		bus.registerListener(this);
 		bus.dispatch(event);
 		bus.removeListener(this);

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

@@ -0,0 +1,33 @@
+package dev.kske.eventbus.core;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests the behavior of the event bus when an {@link ExceptionWrapper} is thrown.
+ *
+ * @author Kai S. K. Engelbart
+ * @since 1.2.1
+ */
+class ExceptionWrapperTest {
+
+	EventBus	bus		= new EventBus();
+	String		event	= "This event will cause an exception";
+
+	/**
+	 * Tests transparent rethrowing of an exception wrapper by {@link EventBus#dispatch(Object)}.
+	 *
+	 * @since 1.2.1
+	 */
+	@Test
+	void testExceptionWrapper() {
+		bus.registerListener(this);
+		assertThrows(ExceptionWrapper.class, () -> bus.dispatch(event));
+	}
+
+	@Event(String.class)
+	void onString() {
+		throw new ExceptionWrapper(new RuntimeException("I failed!"));
+	}
+}

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

@@ -0,0 +1,43 @@
+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. The
+ * effect of handler priorities is also accounted for.
+ *
+ * @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(3, event.getCounter());
+	}
+
+	@Override
+	void onSimpleEventAbstractHandler(SimpleEvent event) {
+		assertSame(1, event.getCounter());
+	}
+
+	@Override
+	public void onSimpleEventInterfaceHandler(SimpleEvent event) {
+		event.increment();
+	}
+
+	@Event
+	@Priority(250)
+	private void onSimpleEventPrivate(SimpleEvent event) {
+		assertSame(0, event.getCounter());
+		event.increment();
+	}
+}

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

@@ -10,7 +10,7 @@ import org.junit.jupiter.api.*;
  * @author Kai S. K. Engelbart
  * @since 1.2.0
  */
-public class NestedTest {
+class NestedTest {
 
 	EventBus	bus;
 	boolean		nestedHit;
@@ -21,7 +21,7 @@ public class NestedTest {
 	 * @since 1.2.0
 	 */
 	@BeforeEach
-	public void registerListener() {
+	void registerListener() {
 		bus = new EventBus();
 		bus.registerListener(this);
 	}
@@ -34,7 +34,7 @@ public class NestedTest {
 	 * @since 1.2.0
 	 */
 	@Test
-	public void testNestedDispatch() {
+	void testNestedDispatch() {
 		bus.dispatch(new SimpleEvent());
 		assertTrue(nestedHit);
 	}

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

@@ -0,0 +1,31 @@
+package dev.kske.eventbus.core;
+
+/**
+ * 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 {
+
+	private int counter;
+
+	@Override
+	public String toString() {
+		return String.format("%s[%d]", getClass().getSimpleName(), counter);
+	}
+
+	void increment() {
+		++counter;
+	}
+
+	int getCounter() {
+		return counter;
+	}
+
+	void reset() {
+		counter = 0;
+	}
+}

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

@@ -0,0 +1,25 @@
+package dev.kske.eventbus.core;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * An abstract class defining a package-private and a private handler for {@link SimpleEvent}.
+ *
+ * @author Kai S. K. Engelbart
+ * @since 1.3.0
+ */
+@Priority(200)
+abstract class SimpleEventListenerBase {
+
+	@Event
+	void onSimpleEventAbstractHandler(SimpleEvent event) {
+		fail("This handler should not be invoked");
+	}
+
+	@Event
+	@Priority(150)
+	private void onSimpleEventPrivate(SimpleEvent event) {
+		assertSame(1, event.getCounter());
+		event.increment();
+	}
+}

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

@@ -0,0 +1,14 @@
+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 {
+
+	@Priority(120)
+	@Event
+	void onSimpleEventInterfaceHandler(SimpleEvent event);
+}

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

@@ -6,4 +6,4 @@ package dev.kske.eventbus.core;
  * @author Kai S. K. Engelbart
  * @since 0.0.4
  */
-public class SimpleEventSub extends SimpleEvent {}
+class SimpleEventSub extends SimpleEvent {}

event-bus-core/pom.xml

@@ -1,39 +0,0 @@
-<project xmlns="http://maven.apache.org/POM/4.0.0"
-	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
-	<modelVersion>4.0.0</modelVersion>
-
-	<artifactId>event-bus-core</artifactId>
-	<name>Event Bus Core</name>
-
-	<parent>
-		<groupId>dev.kske</groupId>
-		<artifactId>event-bus</artifactId>
-		<version>1.2.0</version>
-	</parent>
-
-	<dependencies>
-		<dependency>
-			<groupId>org.junit.jupiter</groupId>
-			<artifactId>junit-jupiter-api</artifactId>
-			<version>5.8.1</version>
-			<scope>test</scope>
-		</dependency>
-	</dependencies>
-
-	<build>
-
-		<!-- Disable resource folder -->
-		<resources />
-
-		<!-- Run unit tests -->
-		<plugins>
-			<plugin>
-				<groupId>org.apache.maven.plugins</groupId>
-				<artifactId>maven-surefire-plugin</artifactId>
-				<version>3.0.0-M5</version>
-			</plugin>
-		</plugins>
-
-	</build>
-</project>

event-bus-core/src/test/java/dev/kske/eventbus/core/SimpleEvent.java

@@ -1,9 +0,0 @@
-package dev.kske.eventbus.core;
-
-/**
- * A simple event for testing purposes.
- *
- * @author Kai S. K. Engelbart
- * @since 0.0.1
- */
-public class SimpleEvent {}

pom.xml

@@ -13,8 +13,8 @@
 	<url>https://git.kske.dev/kske/event-bus</url>
 
 	<modules>
-		<module>event-bus-core</module>
-		<module>event-bus-proc</module>
+		<module>core</module>
+		<module>proc</module>
 	</modules>
 
 	<licenses>

proc/.classpath

@@ -16,17 +16,17 @@
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry kind="src" output="target/test-classes" path="home/kske/git/event-bus/event-bus-ap">
+	<classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" output="target/test-classes" path="src/test/java">
 		<attributes>
 			<attribute name="optional" value="true"/>
 			<attribute name="maven.pomderived" value="true"/>
 			<attribute name="test" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
-		<attributes>
-			<attribute name="maven.pomderived" value="true"/>
-		</attributes>
-	</classpathentry>
 	<classpathentry kind="output" path="target/classes"/>
 </classpath>

proc/pom.xml

@@ -24,9 +24,6 @@
 
 	<build>
 
-		<!-- Disable test folder -->
-		<testSourceDirectory />
-
 		<plugins>
 
 			<!-- Prevent annotation processing error during compilation -->

proc/src/main/java/dev/kske/eventbus/proc/EventProcessor.java

@@ -47,13 +47,12 @@ public class EventProcessor extends AbstractProcessor {
 
 				// Task failed successfully
 				eventType		= e.getTypeMirror();
-				useParameter	= processingEnv.getTypeUtils().isSameType(eventType,
-					getTypeMirror(Event.USE_PARAMETER.class));
+				useParameter	= eventType.getKind() == TypeKind.VOID;
 			}
 
 			// Check handler signature
 			boolean pass = false;
-			if (useParameter && eventHandler.getParameters().size() == 0)
+			if (useParameter && eventHandler.getParameters().isEmpty())
 				error(eventHandler, "The method or the annotation must define the event type");
 			else if (!useParameter && eventHandler.getParameters().size() == 1)
 				error(eventHandler,
@@ -107,7 +106,8 @@ public class EventProcessor extends AbstractProcessor {
 				polymorphic = eventHandler.getAnnotation(Polymorphic.class).value();
 
 			// Effective priority
-			int priority = hasListenerPriority ? listenerPriority.value() : defPriority;
+			int		priority			=
+				hasListenerPriority ? listenerPriority.value() : defPriority;
 			boolean	hasHandlerPriority	= eventHandler.getAnnotation(Priority.class) != null;
 			if (hasHandlerPriority)
 				priority = eventHandler.getAnnotation(Priority.class).value();
@@ -137,14 +137,6 @@ public class EventProcessor extends AbstractProcessor {
 		}
 	}
 
-	private TypeMirror getTypeMirror(Class<?> clazz) {
-		return getTypeElement(clazz).asType();
-	}
-
-	private TypeElement getTypeElement(Class<?> clazz) {
-		return processingEnv.getElementUtils().getTypeElement(clazz.getCanonicalName());
-	}
-
 	private void warning(Element e, String msg, Object... args) {
 		processingEnv.getMessager().printMessage(Kind.WARNING, String.format(msg, args), e);
 	}

proc/src/main/java/module-info.java

@@ -5,7 +5,7 @@
  * @author Kai S. K. Engelbart
  * @since 1.0.0
  */
-module dev.kske.eventbus.ap {
+module dev.kske.eventbus.proc {
 
 	requires java.compiler;
 	requires dev.kske.eventbus.core;