diff --git a/README.md b/README.md index 1f78bcc..1ac86e1 100644 --- a/README.md +++ b/README.md @@ -221,6 +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. diff --git a/core/src/main/java/dev/kske/eventbus/core/EventBus.java b/core/src/main/java/dev/kske/eventbus/core/EventBus.java index 83bef93..334dd52 100644 --- a/core/src/main/java/dev/kske/eventbus/core/EventBus.java +++ b/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.*; *

* A singleton instance of this class can be lazily created and acquired using the * {@link EventBus#getInstance()} method. - *

- * This is a thread-safe implementation. * + * @implNote This is a thread-safe implementation. * @author Kai S. K. Engelbart * @since 0.0.1 * @see Event @@ -237,7 +237,7 @@ 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 @@ -257,6 +257,49 @@ 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 getHandlerMethods(Class listenerClass) { + + // Get methods declared by the listener + Set 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 getMethodsAnnotatedWith(Class enclosingClass, + Class annotationClass) { + var methods = new HashSet(); + 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}. diff --git a/core/src/main/java/dev/kske/eventbus/core/Polymorphic.java b/core/src/main/java/dev/kske/eventbus/core/Polymorphic.java index 1f77726..ec39121 100644 --- a/core/src/main/java/dev/kske/eventbus/core/Polymorphic.java +++ b/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 { diff --git a/core/src/main/java/dev/kske/eventbus/core/Priority.java b/core/src/main/java/dev/kske/eventbus/core/Priority.java index ca82fa3..e180e0f 100644 --- a/core/src/main/java/dev/kske/eventbus/core/Priority.java +++ b/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 { diff --git a/core/src/test/java/dev/kske/eventbus/core/InheritanceTest.java b/core/src/test/java/dev/kske/eventbus/core/InheritanceTest.java new file mode 100644 index 0000000..b72438d --- /dev/null +++ b/core/src/test/java/dev/kske/eventbus/core/InheritanceTest.java @@ -0,0 +1,42 @@ +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 + private void onSimpleEventPrivate(SimpleEvent event) { + assertSame(0, event.getCounter()); + event.increment(); + } +} diff --git a/core/src/test/java/dev/kske/eventbus/core/SimpleEvent.java b/core/src/test/java/dev/kske/eventbus/core/SimpleEvent.java index 2baf080..1512107 100644 --- a/core/src/test/java/dev/kske/eventbus/core/SimpleEvent.java +++ b/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; + } +} diff --git a/core/src/test/java/dev/kske/eventbus/core/SimpleEventListenerBase.java b/core/src/test/java/dev/kske/eventbus/core/SimpleEventListenerBase.java new file mode 100644 index 0000000..1540655 --- /dev/null +++ b/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"); + } + + @Priority(150) + @Event + private void onSimpleEventPrivate(SimpleEvent event) { + assertSame(1, event.getCounter()); + event.increment(); + } +} diff --git a/core/src/test/java/dev/kske/eventbus/core/SimpleEventListenerInterface.java b/core/src/test/java/dev/kske/eventbus/core/SimpleEventListenerInterface.java new file mode 100644 index 0000000..8766e34 --- /dev/null +++ b/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); +}