Своя реализация EventBus

core/src/main/java/mc/core/eventbus/EventBus.java

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+package mc.core.eventbus;
+
+import javafx.util.Pair;
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+import java.lang.reflect.Method;
+import java.util.*;
+import java.util.stream.Stream;
+
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
+public class EventBus {
+    @Getter
+    private static final EventBus insnance = new EventBus();
+
+    private Queue<Event> eventQueue;
+    private Map<Class<? extends Event>, List<Pair<Object, Method>>> subscribes = new HashMap<>();
+
+    @SuppressWarnings("unchecked")
+    public void registerSubscribes(Object subscriberObject) {
+        Stream.of(subscriberObject.getClass().getDeclaredMethods())
+                .filter(method -> method.isAnnotationPresent(Subscriber.class))
+                .filter(method -> method.getReturnType().equals(Void.TYPE))
+                .filter(method -> method.getParameterCount() == 1)
+                .filter(method -> Event.class.isAssignableFrom(method.getParameterTypes()[0]))
+                .forEach(method -> {
+                    Class<? extends Event> type = (Class<? extends Event>) method.getParameterTypes()[0];
+                    List<Pair<Object, Method>> pairs;
+                    if (subscribes.containsKey(type)) {
+                        pairs = subscribes.get(type);
+                    } else {
+                        pairs = new ArrayList<>();
+                        subscribes.put(type, pairs);
+                    }
+                    pairs.add(new Pair<>(subscriberObject, method));
+                });
+    }
+}

core/src/main/java/mc/core/eventbus/Subscriber.java

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+package mc.core.eventbus;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target(value= ElementType.METHOD)
+@Retention(value= RetentionPolicy.RUNTIME)
+public @interface Subscriber {
+}

core/src/test/java/mc/core/TestEventBus.java

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+package mc.core;
+
+import javafx.util.Pair;
+import mc.core.eventbus.Event;
+import mc.core.eventbus.EventBus;
+import mc.core.eventbus.Subscriber;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.mockito.internal.util.reflection.Whitebox;
+
+import java.lang.reflect.Method;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class TestEventBus {
+
+    @SuppressWarnings("unchecked")
+    @Test
+    void testRegisterSubscribes() {
+        DumbEventHandler handler = new DumbEventHandler();
+        EventBus.getInsnance().registerSubscribes(handler);
+
+        Map<Object, List<Pair<Object, Method>>> subscribes =
+                (Map<Object, List<Pair<Object, Method>>>)
+                        Whitebox.getInternalState(EventBus.getInsnance(), "subscribes");
+        assertEquals(1, subscribes.size());
+
+        List<Pair<Object, Method>> pairs = subscribes.values().iterator().next();
+        assertEquals(1, pairs.size());
+
+        Pair<Object, Method> pair = pairs.get(0);
+        assertSame(handler, pair.getKey());
+        assertEquals("corectSubscribe", pair.getValue().getName());
+    }
+
+    private class DumbEvent implements Event {
+    }
+
+    private class DumbEventHandler {
+        @Subscriber
+        public void corectSubscribe(DumbEvent event) {
+        }
+
+        @Subscriber
+        public Object incorectSubscribeReturnType(DumbEvent event) {
+            return null;
+        }
+
+        @Subscriber
+        public void incorrectSubscriberTypeParameter(Object object) {
+        }
+
+        @Subscriber
+        public void incorrectSubscriberManyParameters(DumbEvent event, Object object) {
+        }
+
+        public void someMethod() {
+        }
+    }
+}