preparing event bus

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

bus/build.gradle.kts

@@ -0,0 +1,6 @@
+description = "Umbrella : Messagebus"
+
+dependencies{
+    implementation(project(":core"))
+}
+

bus/src/main/java/de/srsoftware/umbrella/messagebus/Event.java

@@ -0,0 +1,4 @@
+package de.srsoftware.umbrella.messagebus;
+
+public class Event {
+}

bus/src/main/java/de/srsoftware/umbrella/messagebus/EventListener.java

@@ -0,0 +1,5 @@
+package de.srsoftware.umbrella.messagebus;
+
+public interface EventListener {
+	public void onEvent(Event event);
+}

bus/src/main/java/de/srsoftware/umbrella/messagebus/MessageBus.java

@@ -0,0 +1,27 @@
+package de.srsoftware.umbrella.messagebus;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class MessageBus {
+	private static MessageBus SINGLETON = new MessageBus();
+	private Set<EventListener> listeners = new HashSet<>();
+
+	private MessageBus(){}
+
+	public void dispatch(Event event){
+		listeners.parallelStream().forEach(l -> l.onEvent(event));
+	}
+
+	public void drop(EventListener listener){
+		listeners.remove(listener);
+	}
+
+	public static MessageBus messageBus(){
+		return SINGLETON;
+	}
+
+	public void register(EventListener listener){
+		listeners.add(listener);
+	}
+}

settings.gradle.kts

@@ -2,6 +2,7 @@ rootProject.name = "Umbrella25"
 
 include("backend")
 include("bookmark")
+include("bus")
 include("company")
 include("contact")
 include("core")