#113 Event Driven Architecture

- initial commit includes a simple and advanced example of Event-driven architecture

event-driven-architecture/src/main/java/com/iluwatar/eda/advanced/App.java

@@ -0,0 +1,10 @@
+package com.iluwatar.eda.advanced;
+
+public class App {
+
+    public static void main(String[] args) {
+        EventDispatcher dispatcher = new EventDispatcher();
+        dispatcher.registerChannel(Event.class, new Handler());
+        dispatcher.dispatch(new Event());
+    }
+}

event-driven-architecture/src/main/java/com/iluwatar/eda/advanced/Channel.java

@@ -0,0 +1,6 @@
+package com.iluwatar.eda.advanced;
+
+
+public interface Channel<E extends Message> {
+    public void dispatch(E message);
+}

event-driven-architecture/src/main/java/com/iluwatar/eda/advanced/DynamicRouter.java

@@ -0,0 +1,6 @@
+package com.iluwatar.eda.advanced;
+
+public interface DynamicRouter<E extends Message> {
+    public void registerChannel(Class<? extends E> contentType, Channel<? extends E> channel);
+    public void dispatch(E content);
+}

event-driven-architecture/src/main/java/com/iluwatar/eda/advanced/Event.java

@@ -0,0 +1,7 @@
+package com.iluwatar.eda.advanced;
+
+public class Event implements Message {
+    public Class<? extends Message> getType() {
+        return getClass();
+    }
+}

event-driven-architecture/src/main/java/com/iluwatar/eda/advanced/EventDispatcher.java

@@ -0,0 +1,21 @@
+package com.iluwatar.eda.advanced;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class EventDispatcher implements DynamicRouter<Event> {
+    private Map<Class<? extends Event>, Handler> handlers;
+
+    public EventDispatcher() {
+        handlers = new HashMap<Class<? extends Event>, Handler>();
+    }
+
+    public void registerChannel(Class<? extends Event> contentType,
+                                Channel<? extends Event> channel) {
+        handlers.put(contentType, (Handler)channel);
+    }
+
+    public void dispatch(Event content) {
+        handlers.get(content.getClass()).dispatch(content);
+    }
+}

event-driven-architecture/src/main/java/com/iluwatar/eda/advanced/Handler.java

@@ -0,0 +1,7 @@
+package com.iluwatar.eda.advanced;
+
+public class Handler implements Channel<Event> {
+    public void dispatch(Event message) {
+        System.out.println(message.getClass());
+    }
+}

event-driven-architecture/src/main/java/com/iluwatar/eda/advanced/Message.java

@@ -0,0 +1,6 @@
+package com.iluwatar.eda.advanced;
+
+
+public interface Message {
+    public Class<? extends Message> getType();
+}

event-driven-architecture/src/main/java/com/iluwatar/eda/simple/App.java

@@ -0,0 +1,38 @@
+package com.iluwatar.eda.simple;
+
+import java.util.LinkedList;
+import java.util.Queue;
+
+/**
+ * Event-driven architecture (EDA) is a software architecture pattern promoting
+ * the production, detection, consumption of, and reaction to events.
+ * <p/>
+ * This main class publishes events to queue. Each event on the queue is consumed
+ * and handled depending on the type defined in the {@link Event}
+ */
+public class App {
+
+    public static void main(String args[]) {
+
+        //create a list of events having different types
+        //add these events to a simple queue
+        Queue<Event> events = new LinkedList<Event>();
+        events.add(new Event('A', "Hello"));
+        events.add(new Event('B', "event-driven"));
+        events.add(new Event('A', "world!"));
+
+        Event e;
+
+        //the event loop will go through the list of events
+        //and handle each one depending on it's type
+        while (!events.isEmpty()) {
+            e = events.remove();
+
+            //handle events depending on their type
+            if (e.type == 'A')
+                EventHandler.handleEventA(e);
+            if (e.type == 'B')
+                EventHandler.handleEventB(e);
+        }
+    }
+}

event-driven-architecture/src/main/java/com/iluwatar/eda/simple/Event.java

@@ -0,0 +1,15 @@
+package com.iluwatar.eda.simple;
+
+/**
+ * The Event class defines the type of event and data related to the event.
+ */
+public class Event {
+
+    public char type;
+    public String data;
+
+    public Event(char type, String data){
+        this.type = type;
+        this.data = data;
+    }
+}

event-driven-architecture/src/main/java/com/iluwatar/eda/simple/EventHandler.java

@@ -0,0 +1,15 @@
+package com.iluwatar.eda.simple;
+
+/**
+ * The {@link EventHandler} class handles performs actions on {@link Event} objects
+ */
+public class EventHandler {
+
+    public static void handleEventA(Event e){
+        System.out.println(e.data);
+    }
+
+    public static void handleEventB(Event e){
+        System.out.println(e.data.toUpperCase());
+    }
+}