Register handlers declared in superclasses and interfaces
This experimental extension to the listener registration process walks the inheritance tree and searches for handler declarations.
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@ -2,9 +2,19 @@ package dev.kske.eventbus.core;
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import java.lang.System.Logger;
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import java.lang.System.Logger.Level;
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import java.lang.annotation.Annotation;
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import java.lang.reflect.InvocationTargetException;
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import java.util.*;
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import java.lang.reflect.Method;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Map;
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import java.util.Objects;
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import java.util.Set;
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import java.util.TreeSet;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.stream.Collectors;
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/**
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* Event listeners can be registered at an event bus to be notified when an event is dispatched.
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@ -188,13 +198,9 @@ public final class EventBus {
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priority = listener.getClass().getAnnotation(Priority.class).value();
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registeredListeners.add(listener);
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for (var method : listener.getClass().getDeclaredMethods()) {
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for (var method : getHandlerMethods(listener.getClass())) {
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Event annotation = method.getAnnotation(Event.class);
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// Skip methods without annotations
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if (annotation == null)
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continue;
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// Initialize and bind the handler
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var handler = new EventHandler(listener, method, annotation, polymorphic, priority);
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bindings.putIfAbsent(handler.getEventType(), new TreeSet<>());
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@ -211,6 +217,44 @@ public final class EventBus {
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listener.getClass().getName());
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}
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/**
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* Searches for event handlers declared inside the inheritance hierarchy of an event listener.
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*
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* This handlers defined in both superclasses and interfaces, regardless of visibility.
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*
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* @param listenerClass the class to inspect
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* @return all event handlers defined for the given listener
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* @since 1.2.0
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*/
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private List<Method> getHandlerMethods(Class<?> listenerClass) {
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// Get declared handlers
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List<Method> methods = getMethodsAnnotatedWith(listenerClass, Event.class);
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// Recursively add superclass handlers
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if(listenerClass.getSuperclass() != null)
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methods.addAll(getHandlerMethods(listenerClass.getSuperclass()));
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// Recursively add handlers defined by interfaces
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for(Class<?> iClass : listenerClass.getInterfaces())
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methods.addAll(getHandlerMethods(iClass));
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return methods;
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}
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/**
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* Searches for methods with a specific annotation declared inside a class.
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*
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* @param enclosingClass the class to inspect
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* @param annotationClass the annotation to look for
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* @return all methods matching the search criteria
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* @since 1.2.0
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*/
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private List<Method> getMethodsAnnotatedWith(Class<?> enclosingClass, Class<? extends Annotation> annotationClass) {
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return Arrays.stream(enclosingClass.getDeclaredMethods())
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.filter(m -> m.isAnnotationPresent(annotationClass)).collect(Collectors.toList());
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}
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/**
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* Removes a specific listener from this event bus.
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*
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@ -0,0 +1,36 @@
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package dev.kske.eventbus.core;
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import static org.junit.jupiter.api.Assertions.*;
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import org.junit.jupiter.api.Test;
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/**
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* Tests whether event handlers correctly handle inheritance.
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*
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* @author Kai S. K. Engelbart
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* @since 1.2.0
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*/
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class InheritanceTest extends SimpleEventListenerBase implements SimpleEventListenerInterface {
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EventBus bus;
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boolean hit;
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@Test
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void test() {
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bus = new EventBus();
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bus.registerListener(this);
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bus.dispatch(new SimpleEvent());
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assertTrue(hit);
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}
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@Override
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@Event(SimpleEvent.class)
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public void onSimpleEventAbstractHandler() {
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System.out.println("Subclass!");
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}
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@Override
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public void onSimpleEventInterfaceHandler() {
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hit = true;
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}
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}
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@ -0,0 +1,23 @@
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package dev.kske.eventbus.core;
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/**
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* An interface defining a single handler for {@link SimpleEvent}.
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*
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* Used for testing event listener inheritance.
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*
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* @author Kai S. K. Engelbart
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* @since 1.2.0
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*/
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abstract class SimpleEventListenerBase {
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@Event(SimpleEvent.class)
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void onSimpleEventAbstractHandler() {
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System.out.println("Test");
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}
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@Event(SimpleEvent.class)
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private void onSimpleEventPrivate() {
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System.out.println("Private Handler!");
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}
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}
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@ -0,0 +1,16 @@
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package dev.kske.eventbus.core;
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/**
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* An interface defining a single handler for {@link SimpleEvent}.
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*
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* Used for testing event listener inheritance.
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*
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* @author Kai S. K. Engelbart
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* @since 1.2.0
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*/
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interface SimpleEventListenerInterface {
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@Event(SimpleEvent.class)
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void onSimpleEventInterfaceHandler();
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}
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