BAEL-2274 DDD Bounded Contexts and Java Modules

ddd-modules/sharedkernel/src/main/java/com/baeldung/dddmodules/sharedkernel/events/ApplicationEvent.java

@@ -0,0 +1,21 @@
+package com.baeldung.dddmodules.sharedkernel.events;
+
+import java.util.Map;
+
+public abstract class ApplicationEvent {
+    protected Map<String, String> payload;
+
+    public abstract String getType();
+
+    public String getPayloadValue(String key) {
+        if (this.payload.containsKey(key)) {
+            return this.payload.get(key);
+        }
+        return "";
+    }
+
+    public ApplicationEvent(Map<String, String> payload) {
+        this.payload = payload;
+    }
+}
+

ddd-modules/sharedkernel/src/main/java/com/baeldung/dddmodules/sharedkernel/events/EventBus.java

@@ -0,0 +1,9 @@
+package com.baeldung.dddmodules.sharedkernel.events;
+
+public interface EventBus {
+    <E extends ApplicationEvent> void publish(E event);
+
+    <E extends ApplicationEvent> void subscribe(String eventType, EventSubscriber subscriber);
+
+    <E extends ApplicationEvent> void unsubscribe(String eventType, EventSubscriber subscriber);
+}

ddd-modules/sharedkernel/src/main/java/com/baeldung/dddmodules/sharedkernel/events/EventSubscriber.java

@@ -0,0 +1,5 @@
+package com.baeldung.dddmodules.sharedkernel.events;
+
+public interface EventSubscriber {
+    <E extends ApplicationEvent> void onEvent(E event);
+}

ddd-modules/sharedkernel/src/main/java/com/baeldung/dddmodules/sharedkernel/service/ApplicationService.java

@@ -0,0 +1,33 @@
+package com.baeldung.dddmodules.sharedkernel.service;
+
+import com.baeldung.dddmodules.sharedkernel.events.ApplicationEvent;
+import com.baeldung.dddmodules.sharedkernel.events.EventBus;
+import com.baeldung.dddmodules.sharedkernel.events.EventSubscriber;
+
+public interface ApplicationService {
+
+    default <E extends ApplicationEvent> void publishEvent(E event) {
+        EventBus eventBus = getEventBus();
+        if (eventBus != null) {
+            eventBus.publish(event);
+        }
+    }
+
+    default <E extends ApplicationEvent> void subscribe(String eventType, EventSubscriber subscriber) {
+        EventBus eventBus = getEventBus();
+        if (eventBus != null) {
+            eventBus.subscribe(eventType, subscriber);
+        }
+    }
+
+    default <E extends ApplicationEvent> void unsubscribe(String eventType, EventSubscriber subscriber) {
+        EventBus eventBus = getEventBus();
+        if (eventBus != null) {
+            eventBus.unsubscribe(eventType, subscriber);
+        }
+    }
+
+    EventBus getEventBus();
+
+    void setEventBus(EventBus eventBus);
+}

ddd-modules/sharedkernel/src/main/java/module-info.java

@@ -0,0 +1,4 @@
+module com.baeldung.dddmodules.sharedkernel {
+    exports com.baeldung.dddmodules.sharedkernel.events;
+    exports com.baeldung.dddmodules.sharedkernel.service;
+}