JAVA-12100: Rename ddd-modules -> ddd-contexts

ddd-contexts/sharedkernel/pom.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung.dddcontexts.sharedkernel</groupId>
+    <artifactId>sharedkernel</artifactId>
+    <version>1.0</version>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.dddcontexts</groupId>
+        <artifactId>ddd-contexts</artifactId>
+        <version>1.0</version>
+    </parent>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${source.version}</source>
+                    <target>${target.version}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <source.version>9</source.version>
+        <target.version>9</target.version>
+    </properties>
+
+</project>

ddd-contexts/sharedkernel/src/main/java/com/baeldung/dddcontexts/sharedkernel/events/ApplicationEvent.java

@@ -0,0 +1,21 @@
+package com.baeldung.dddcontexts.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-contexts/sharedkernel/src/main/java/com/baeldung/dddcontexts/sharedkernel/events/EventBus.java

@@ -0,0 +1,9 @@
+package com.baeldung.dddcontexts.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-contexts/sharedkernel/src/main/java/com/baeldung/dddcontexts/sharedkernel/events/EventSubscriber.java

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

ddd-contexts/sharedkernel/src/main/java/com/baeldung/dddcontexts/sharedkernel/service/ApplicationService.java

@@ -0,0 +1,33 @@
+package com.baeldung.dddcontexts.sharedkernel.service;
+
+import com.baeldung.dddcontexts.sharedkernel.events.ApplicationEvent;
+import com.baeldung.dddcontexts.sharedkernel.events.EventBus;
+import com.baeldung.dddcontexts.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-contexts/sharedkernel/src/main/java/module-info.java

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