#113 Event Driven Architecture

Adds more Javadoc and fixes checkstyle issues.

event-driven-architecture/pom.xml

@@ -19,28 +19,5 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
-    <build>
+
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-checkstyle-plugin</artifactId>
-                <version>2.15</version>
-                <executions>
-                    <execution>
-                        <id>validate</id>
-                        <goals>
-                            <goal>check</goal>
-                        </goals>
-                        <phase>validate</phase>
-                        <configuration>
-                            <configLocation>checkstyle.xml</configLocation>
-                            <encoding>UTF-8</encoding>
-                            <consoleOutput>true</consoleOutput>
-                            <failsOnError>true</failsOnError>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-        </plugins>
-    </build>
 </project>

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

@@ -5,23 +5,37 @@ import com.iluwatar.eda.event.UserCreatedEvent;
 import com.iluwatar.eda.event.UserUpdatedEvent;
 import com.iluwatar.eda.handler.UserCreatedEventHandler;
 import com.iluwatar.eda.handler.UserUpdatedEventHandler;
+import com.iluwatar.eda.model.User;
 
 /**
  * An event-driven architecture (EDA) is a framework that orchestrates behavior around the
  * production, detection and consumption of events as well as the responses they evoke. An event is
  * any identifiable occurrence that has significance for system hardware or software. <p/> The
- * example below we uses an {@link EventDispatcher} to link/register  {@link Event} objects to their
+ * example below uses an {@link EventDispatcher} to link/register {@link Event} objects to their
- * respective handlers Once an {@link Event} is dispatched, it's respective handler is invoked and
+ * respective handlers once an {@link Event} is dispatched, it's respective handler is invoked and
- * the {@link Event} is handled accordingly
+ * the {@link Event} is handled accordingly.
+ *
  */
 public class App {
 
+  /**
+   * Once the {@link EventDispatcher} is initialised, channels related to specific events have to be
+   * made known to the dispatcher by registering them. In this case the {@link UserCreatedEvent} is
+   * bound to the UserCreatedEventHandler, whilst the {@link UserUpdatedEvent} is bound to the
+   * {@link UserUpdatedEventHandler}. The dispatcher can now be called to dispatch specific events.
+   * When a user is saved, the {@link UserCreatedEvent} can be dispatched.
+   * On the other hand, when a user is updated, {@link UserUpdatedEvent} can be dispatched.
+   *
+   */
   public static void main(String[] args) {
+
     EventDispatcher dispatcher = new EventDispatcher();
     dispatcher.registerChannel(UserCreatedEvent.class, new UserCreatedEventHandler());
     dispatcher.registerChannel(UserUpdatedEvent.class, new UserUpdatedEventHandler());
-    dispatcher.dispatch(new UserCreatedEvent());
+
-    dispatcher.dispatch(new UserUpdatedEvent());
+    User user = new User("iluwatar");
+    dispatcher.dispatch(new UserCreatedEvent(user));
+    dispatcher.dispatch(new UserUpdatedEvent(user));
   }
 
 }

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

@@ -8,21 +8,20 @@ import java.util.HashMap;
 import java.util.Map;
 
 /**
- * The {@link Event Dispatcher} handles routing of {@link Event} messages
+ * Handles the routing of {@link Event} messages to associated channels.
- * to associated channels.
  * A {@link HashMap} is used to store the association between events and their respective handlers.
  *
  */
 public class EventDispatcher implements DynamicRouter<Event> {
 
-  private Map<Class<? extends Event>, Channel> handlers;
+  private Map<Class<? extends Event>, Channel<?>> handlers;
 
   public EventDispatcher() {
     handlers = new HashMap<>();
   }
 
   /**
-   * Links an {@link Event} to a specific {@link Channel}
+   * Links an {@link Event} to a specific {@link Channel}.
    *
    * @param contentType The {@link Event} to be registered
    * @param channel     The {@link Channel} that will be handling the {@link Event}

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

@@ -1,8 +1,22 @@
 package com.iluwatar.eda.event;
 
+import com.iluwatar.eda.model.User;
+
 /**
  * The {@link UserCreatedEvent} class should should be dispatched whenever a user has been created.
- * This class can be extended to contain details about the user has been created.
+ * This class can be extended to contain details about the user has been created. In this example,
+ * the entire {@link User} object is passed on as data with the event.
  */
 public class UserCreatedEvent extends Event {
+
+  private User user;
+
+  public UserCreatedEvent(User user) {
+    this.user = user;
+  }
+
+
+  public User getUser() {
+    return user;
+  }
 }

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

@@ -1,8 +1,21 @@
 package com.iluwatar.eda.event;
 
+import com.iluwatar.eda.model.User;
+
 /**
  * The {@link UserUpdatedEvent} class should should be dispatched whenever a user has been updated.
- * This class can be extended to contain details about the user has been updated.
+ * This class can be extended to contain details about the user has been updated. In this example,
+ * the entire {@link User} object is passed on as data with the event.
  */
 public class UserUpdatedEvent extends Event {
+
+  private User user;
+
+  public UserUpdatedEvent(User user) {
+    this.user = user;
+  }
+
+  public User getUser() {
+    return user;
+  }
 }

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

@@ -7,5 +7,5 @@ import com.iluwatar.eda.event.Event;
  * of message
  */
 public interface Channel<E extends Message> {
-  void dispatch(E message);
+  void dispatch(Event message);
 }

event-driven-architecture/src/main/java/com/iluwatar/eda/handler/UserCreatedEventHandler.java

@@ -1,13 +1,19 @@
 package com.iluwatar.eda.handler;
 
+import com.iluwatar.eda.event.Event;
 import com.iluwatar.eda.event.UserCreatedEvent;
 import com.iluwatar.eda.framework.Channel;
+import com.iluwatar.eda.model.User;
 
 /**
  * Handles the {@link UserCreatedEvent} message.
  */
 public class UserCreatedEventHandler implements Channel<UserCreatedEvent> {
-  public void dispatch(UserCreatedEvent message) {
+
-    System.out.println("User Created!");
+  @Override
+  public void dispatch(Event message) {
+
+    UserCreatedEvent userCreatedEvent = (UserCreatedEvent) message;
+    System.out.printf("User with %s has been Created!", userCreatedEvent.getUser().getUsername());
   }
 }

event-driven-architecture/src/main/java/com/iluwatar/eda/handler/UserUpdatedEventHandler.java

@@ -1,5 +1,7 @@
 package com.iluwatar.eda.handler;
 
+import com.iluwatar.eda.event.Event;
+import com.iluwatar.eda.event.UserCreatedEvent;
 import com.iluwatar.eda.event.UserUpdatedEvent;
 import com.iluwatar.eda.framework.Channel;
 
@@ -7,7 +9,11 @@ import com.iluwatar.eda.framework.Channel;
  * Handles the {@link UserUpdatedEvent} message.
  */
 public class UserUpdatedEventHandler implements Channel<UserUpdatedEvent> {
-  public void dispatch(UserUpdatedEvent message) {
+
-    System.out.println("User Updated!");
+  @Override
+  public void dispatch(Event message) {
+
+    UserUpdatedEvent userUpdatedEvent = (UserUpdatedEvent) message;
+    System.out.printf("User with %s has been Updated!", userUpdatedEvent.getUser().getUsername());
   }
 }

event-driven-architecture/src/main/java/com/iluwatar/eda/model/User.java

@@ -0,0 +1,21 @@
+package com.iluwatar.eda.model;
+
+import com.iluwatar.eda.event.UserCreatedEvent;
+import com.iluwatar.eda.event.UserUpdatedEvent;
+
+/**
+ * This {@link User} class is a basic pojo used to demonstrate user data sent along with
+ * the {@link UserCreatedEvent} and {@link UserUpdatedEvent} events.
+ */
+public class User {
+
+  private String username;
+
+  public User(String username) {
+    this.username = username;
+  }
+
+  public String getUsername() {
+    return username;
+  }
+}