From 998fc3a91eb050d1b0e28fde95646ef13dd14fcf Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Fri, 3 Jan 2020 16:40:43 +0200
Subject: [PATCH 1/7] Moved classes related to java-nio-server to
 envoy.server.net package.

---
 src/main/java/envoy/server/Startup.java              |  3 +++
 .../server/{ => net}/ObjectMessageProcessor.java     |  4 +++-
 .../envoy/server/{ => net}/ObjectMessageReader.java  | 12 ++++++------
 3 files changed, 12 insertions(+), 7 deletions(-)
 rename src/main/java/envoy/server/{ => net}/ObjectMessageProcessor.java (97%)
 rename src/main/java/envoy/server/{ => net}/ObjectMessageReader.java (98%)

diff --git a/src/main/java/envoy/server/Startup.java b/src/main/java/envoy/server/Startup.java
index 58a8366..dd295a4 100644
--- a/src/main/java/envoy/server/Startup.java
+++ b/src/main/java/envoy/server/Startup.java
@@ -6,6 +6,9 @@ import java.util.Set;
 
 import com.jenkov.nioserver.Server;
 
+import envoy.server.net.ObjectMessageProcessor;
+import envoy.server.net.ObjectMessageReader;
+
 /**
  * Starts the server.<br>
  * <br>
diff --git a/src/main/java/envoy/server/ObjectMessageProcessor.java b/src/main/java/envoy/server/net/ObjectMessageProcessor.java
similarity index 97%
rename from src/main/java/envoy/server/ObjectMessageProcessor.java
rename to src/main/java/envoy/server/net/ObjectMessageProcessor.java
index 53e53da..6f652d9 100644
--- a/src/main/java/envoy/server/ObjectMessageProcessor.java
+++ b/src/main/java/envoy/server/net/ObjectMessageProcessor.java
@@ -1,4 +1,4 @@
-package envoy.server;
+package envoy.server.net;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
@@ -11,6 +11,8 @@ import com.jenkov.nioserver.IMessageProcessor;
 import com.jenkov.nioserver.Message;
 import com.jenkov.nioserver.WriteProxy;
 
+import envoy.server.ObjectProcessor;
+
 /**
  * Handles incoming objects.<br>
  * <br>
diff --git a/src/main/java/envoy/server/ObjectMessageReader.java b/src/main/java/envoy/server/net/ObjectMessageReader.java
similarity index 98%
rename from src/main/java/envoy/server/ObjectMessageReader.java
rename to src/main/java/envoy/server/net/ObjectMessageReader.java
index f0fa73a..b477734 100644
--- a/src/main/java/envoy/server/ObjectMessageReader.java
+++ b/src/main/java/envoy/server/net/ObjectMessageReader.java
@@ -1,4 +1,4 @@
-package envoy.server;
+package envoy.server.net;
 
 import java.io.IOException;
 import java.nio.ByteBuffer;
@@ -26,11 +26,6 @@ public class ObjectMessageReader implements IMessageReader {
 	private Message			nextMessage;
 	private MessageBuffer	messageBuffer;
 
-	private int fromByteArray(byte[] bytes, int offset) {
-		return ((bytes[offset] & 0xFF) << 24) | ((bytes[offset + 1] & 0xFF) << 16) | ((bytes[offset + 2] & 0xFF) << 8)
-				| ((bytes[offset + 3] & 0xFF) << 0);
-	}
-
 	@Override
 	public List<Message> getMessages() { return completeMessages; }
 
@@ -65,4 +60,9 @@ public class ObjectMessageReader implements IMessageReader {
 
 		buffer.clear();
 	}
+
+	private int fromByteArray(byte[] bytes, int offset) {
+		return ((bytes[offset] & 0xFF) << 24) | ((bytes[offset + 1] & 0xFF) << 16) | ((bytes[offset + 2] & 0xFF) << 8)
+				| ((bytes[offset + 3] & 0xFF) << 0);
+	}
 }
\ No newline at end of file

From c42bdffbd7d02c13df41e0ecefaa6f8b2342c789 Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Fri, 3 Jan 2020 18:11:38 +0200
Subject: [PATCH 2/7] Added ConnectionManager, propagating socketId to
 processors

---
 .../java/envoy/server/ConnectionManager.java  | 79 +++++++++++++++++++
 .../server/LoginCredentialProcessor.java      |  8 +-
 .../java/envoy/server/MessageProcessor.java   | 12 ++-
 .../java/envoy/server/ObjectProcessor.java    |  5 +-
 src/main/java/envoy/server/Startup.java       |  2 +
 .../server/net/ObjectMessageProcessor.java    |  8 +-
 6 files changed, 105 insertions(+), 9 deletions(-)
 create mode 100644 src/main/java/envoy/server/ConnectionManager.java

diff --git a/src/main/java/envoy/server/ConnectionManager.java b/src/main/java/envoy/server/ConnectionManager.java
new file mode 100644
index 0000000..ac4b0c0
--- /dev/null
+++ b/src/main/java/envoy/server/ConnectionManager.java
@@ -0,0 +1,79 @@
+package envoy.server;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+import com.jenkov.nioserver.ISocketIdListener;
+
+/**
+ * Project: <strong>envoy-server-standalone</strong><br>
+ * File: <strong>ConnectionManager.java</strong><br>
+ * Created: <strong>03.01.2020</strong><br>
+ * 
+ * @author Kai S. K. Engelbart
+ * @since Envoy Server Standalone v0.1-alpha
+ */
+public class ConnectionManager implements ISocketIdListener {
+
+	/**
+	 * Contains all socket IDs that have not yet performed a handshake / acquired
+	 * their corresponding user ID.
+	 * 
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	private Set<Long> pendingSockets = new HashSet<>();
+
+	/**
+	 * Contains all socket IDs that have acquired a user ID as keys to these IDs.
+	 * 
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	private Map<Long, Long> sockets = new HashMap<>();
+
+	private static ConnectionManager connectionManager = new ConnectionManager();
+
+	private ConnectionManager() {}
+
+	/**
+	 * @return a singleton instance of this object
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public static ConnectionManager getInstance() { return connectionManager; }
+
+	@Override
+	public void socketCancelled(long socketId) {
+		if (!pendingSockets.remove(socketId))
+			sockets.entrySet().stream().filter(e -> e.getValue() == socketId).forEach(e -> sockets.remove(e.getValue()));
+	}
+
+	@Override
+	public void socketRegistered(long socketId) { pendingSockets.add(socketId); }
+
+	/**
+	 * Associates a socket ID with a user ID.
+	 * 
+	 * @param socketId the socket ID
+	 * @param userId   the user ID
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public void registerUser(long socketId, long userId) {
+		sockets.put(socketId, userId);
+		pendingSockets.remove(socketId);
+	}
+
+	/**
+	 * @param userId the ID of the user registered at the a socket
+	 * @return the ID of the socket
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public long getSocketId(long userId) { return sockets.get(userId); }
+
+	/**
+	 * @param userId the ID of the user to check for
+	 * @return {@code true} if the user is online
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public boolean isOnline(long userId) { return sockets.containsKey(userId); }
+}
diff --git a/src/main/java/envoy/server/LoginCredentialProcessor.java b/src/main/java/envoy/server/LoginCredentialProcessor.java
index f208a3e..0a84edf 100644
--- a/src/main/java/envoy/server/LoginCredentialProcessor.java
+++ b/src/main/java/envoy/server/LoginCredentialProcessor.java
@@ -22,8 +22,10 @@ public class LoginCredentialProcessor implements ObjectProcessor<LoginCredential
 	public Class<LoginCredentials> getInputClass() { return LoginCredentials.class; }
 
 	@Override
-	public User process(LoginCredentials input) {
-		System.out.println("Received login credentials " + input);
-		return new User(currentUserId++, input.getName());
+	public User process(LoginCredentials input, long socketId) {
+		System.out.println(String.format("Received login credentials %s from socket ID %d", input, socketId));
+		User user = new User(currentUserId++, input.getName());
+		ConnectionManager.getInstance().registerUser(socketId, user.getId());
+		return user;
 	}
 }
diff --git a/src/main/java/envoy/server/MessageProcessor.java b/src/main/java/envoy/server/MessageProcessor.java
index ea52c55..8d80e53 100644
--- a/src/main/java/envoy/server/MessageProcessor.java
+++ b/src/main/java/envoy/server/MessageProcessor.java
@@ -18,5 +18,15 @@ public class MessageProcessor implements ObjectProcessor<Message, Void> {
 	public Class<Message> getInputClass() { return Message.class; }
 
 	@Override
-	public Void process(Message input) { return null; }
+	public Void process(Message message, long socketId) {
+
+		// TODO: Send message to recipient if online
+		ConnectionManager connectionManager = ConnectionManager.getInstance();
+		if (connectionManager.isOnline(message.getRecipientId())) {
+
+		}
+
+		// TODO: Add message to database
+		return null;
+	}
 }
diff --git a/src/main/java/envoy/server/ObjectProcessor.java b/src/main/java/envoy/server/ObjectProcessor.java
index 44c07e1..07c0480 100644
--- a/src/main/java/envoy/server/ObjectProcessor.java
+++ b/src/main/java/envoy/server/ObjectProcessor.java
@@ -22,9 +22,10 @@ public interface ObjectProcessor<T, U> {
 	Class<T> getInputClass();
 
 	/**
-	 * @param input the request object
+	 * @param input    the request object
+	 * @param socketId the ID of the socket from which the object was received
 	 * @return the response object
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
-	U process(T input);
+	U process(T input, long socketId);
 }
\ No newline at end of file
diff --git a/src/main/java/envoy/server/Startup.java b/src/main/java/envoy/server/Startup.java
index dd295a4..b616946 100644
--- a/src/main/java/envoy/server/Startup.java
+++ b/src/main/java/envoy/server/Startup.java
@@ -32,7 +32,9 @@ public class Startup {
 		Set<ObjectProcessor<?, ?>> processors = new HashSet<>();
 		processors.add(new LoginCredentialProcessor());
 		processors.add(new MessageProcessor());
+
 		Server server = new Server(8080, () -> new ObjectMessageReader(), new ObjectMessageProcessor(processors));
 		server.start();
+		server.getSocketProcessor().registerSocketIdListener(ConnectionManager.getInstance());
 	}
 }
\ No newline at end of file
diff --git a/src/main/java/envoy/server/net/ObjectMessageProcessor.java b/src/main/java/envoy/server/net/ObjectMessageProcessor.java
index 6f652d9..1bf707f 100644
--- a/src/main/java/envoy/server/net/ObjectMessageProcessor.java
+++ b/src/main/java/envoy/server/net/ObjectMessageProcessor.java
@@ -25,7 +25,7 @@ import envoy.server.ObjectProcessor;
  */
 public class ObjectMessageProcessor implements IMessageProcessor {
 
-	private final Set<ObjectProcessor<?, ?>> processors;
+	private final Set<ObjectProcessor<?, ?>>	processors;
 
 	/**
 	 * The constructor to set the {@link ObjectProcessor}s.
@@ -33,7 +33,9 @@ public class ObjectMessageProcessor implements IMessageProcessor {
 	 * @param processors the {@link ObjectProcessor} to set
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
-	public ObjectMessageProcessor(Set<ObjectProcessor<?, ?>> processors) { this.processors = processors; }
+	public ObjectMessageProcessor(Set<ObjectProcessor<?, ?>> processors) {
+		this.processors			= processors;
+	}
 
 	@SuppressWarnings("unchecked")
 	@Override
@@ -44,7 +46,7 @@ public class ObjectMessageProcessor implements IMessageProcessor {
 
 			// Process object
 			processors.stream().filter(p -> p.getInputClass().isInstance(obj)).forEach((@SuppressWarnings("rawtypes") ObjectProcessor p) -> {
-				Object responseObj = p.process(p.getInputClass().cast(obj));
+				Object responseObj = p.process(p.getInputClass().cast(obj), message.socketId);
 				if (responseObj != null) {
 					// Create message targeted at the client
 					Message response = writeProxy.getMessage();

From 242593472ed4869eb29aeb49c1a9accae323d945 Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Mon, 6 Jan 2020 14:58:28 +0200
Subject: [PATCH 3/7] Added writing capabilities to ObjectProcessor, completed
 db integration

At this moment the client is not able to receive to objects sent
consecutively. This will be worked on in a future commit and should be
fixed before merging this branch into develop.
---
 pom.xml                                       |  5 +++
 .../server/LoginCredentialProcessor.java      | 21 ++++++++++--
 .../java/envoy/server/MessageProcessor.java   |  6 ++--
 .../java/envoy/server/ObjectProcessor.java    | 11 +++---
 src/main/java/envoy/server/data/Message.java  | 20 +++++++++--
 src/main/java/envoy/server/data/User.java     |  6 +++-
 .../server/net/ObjectMessageProcessor.java    | 32 ++++++-----------
 .../envoy/server/net/ObjectWriteProxy.java    | 34 +++++++++++++++++++
 src/main/resources/META-INF/persistence.xml   | 29 ++++++++++++++++
 9 files changed, 128 insertions(+), 36 deletions(-)
 create mode 100644 src/main/java/envoy/server/net/ObjectWriteProxy.java
 create mode 100644 src/main/resources/META-INF/persistence.xml

diff --git a/pom.xml b/pom.xml
index 5b81ded..48a6be0 100644
--- a/pom.xml
+++ b/pom.xml
@@ -33,6 +33,11 @@
 			<artifactId>hibernate-core</artifactId>
 			<version>5.4.10.Final</version>
 		</dependency>
+		<dependency>
+			<groupId>org.postgresql</groupId>
+			<artifactId>postgresql</artifactId>
+			<version>42.2.9</version>
+		</dependency>
 	</dependencies>
 
 	<build>
diff --git a/src/main/java/envoy/server/LoginCredentialProcessor.java b/src/main/java/envoy/server/LoginCredentialProcessor.java
index 0a84edf..89261cf 100644
--- a/src/main/java/envoy/server/LoginCredentialProcessor.java
+++ b/src/main/java/envoy/server/LoginCredentialProcessor.java
@@ -1,7 +1,12 @@
 package envoy.server;
 
+import java.io.IOException;
+import java.util.ArrayList;
+
+import envoy.data.Contacts;
 import envoy.data.LoginCredentials;
 import envoy.data.User;
+import envoy.server.net.ObjectWriteProxy;
 
 /**
  * This {@link ObjectProcessor} handles {@link LoginCredentials}.<br>
@@ -13,7 +18,7 @@ import envoy.data.User;
  * @author Kai S. K. Engelbart
  * @since Envoy Server Standalone v0.1-alpha
  */
-public class LoginCredentialProcessor implements ObjectProcessor<LoginCredentials, User> {
+public class LoginCredentialProcessor implements ObjectProcessor<LoginCredentials> {
 
 	// TODO: Acquire user IDs from database
 	private static long currentUserId = 1;
@@ -22,10 +27,20 @@ public class LoginCredentialProcessor implements ObjectProcessor<LoginCredential
 	public Class<LoginCredentials> getInputClass() { return LoginCredentials.class; }
 
 	@Override
-	public User process(LoginCredentials input, long socketId) {
+	public void process(LoginCredentials input, long socketId, ObjectWriteProxy writeProxy) throws IOException {
 		System.out.println(String.format("Received login credentials %s from socket ID %d", input, socketId));
+
+		// Create user
 		User user = new User(currentUserId++, input.getName());
 		ConnectionManager.getInstance().registerUser(socketId, user.getId());
-		return user;
+
+		// Create contacts
+		Contacts contacts = new Contacts(user.getId(), new ArrayList<>());
+
+		// Complete handshake
+		System.out.println("Sending user...");
+		writeProxy.write(socketId, user);
+		System.out.println("Sending contacts...");
+		writeProxy.write(socketId, contacts);
 	}
 }
diff --git a/src/main/java/envoy/server/MessageProcessor.java b/src/main/java/envoy/server/MessageProcessor.java
index 8d80e53..3e2f139 100644
--- a/src/main/java/envoy/server/MessageProcessor.java
+++ b/src/main/java/envoy/server/MessageProcessor.java
@@ -1,6 +1,7 @@
 package envoy.server;
 
 import envoy.data.Message;
+import envoy.server.net.ObjectWriteProxy;
 
 /**
  * This {@link ObjectProcessor} handles incoming {@link Message}s.<br>
@@ -12,13 +13,13 @@ import envoy.data.Message;
  * @author Kai S. K. Engelbart
  * @since Envoy Server Standalone v0.1-alpha
  */
-public class MessageProcessor implements ObjectProcessor<Message, Void> {
+public class MessageProcessor implements ObjectProcessor<Message> {
 
 	@Override
 	public Class<Message> getInputClass() { return Message.class; }
 
 	@Override
-	public Void process(Message message, long socketId) {
+	public void process(Message message, long socketId, ObjectWriteProxy writeProxy) {
 
 		// TODO: Send message to recipient if online
 		ConnectionManager connectionManager = ConnectionManager.getInstance();
@@ -27,6 +28,5 @@ public class MessageProcessor implements ObjectProcessor<Message, Void> {
 		}
 
 		// TODO: Add message to database
-		return null;
 	}
 }
diff --git a/src/main/java/envoy/server/ObjectProcessor.java b/src/main/java/envoy/server/ObjectProcessor.java
index 07c0480..0221fc0 100644
--- a/src/main/java/envoy/server/ObjectProcessor.java
+++ b/src/main/java/envoy/server/ObjectProcessor.java
@@ -1,5 +1,9 @@
 package envoy.server;
 
+import java.io.IOException;
+
+import envoy.server.net.ObjectWriteProxy;
+
 /**
  * This interface defines methods for processing objects of a specific
  * type incoming from a client.<br>
@@ -10,13 +14,12 @@ package envoy.server;
  *
  * @author Kai S. K. Engelbart
  * @param <T> type of the request object
- * @param <U> type of the response object
  * @since Envoy Server Standalone v0.1-alpha
  */
-public interface ObjectProcessor<T, U> {
+public interface ObjectProcessor<T> {
 
 	/**
-	 * @return the Class of the request object
+	 * @return the class of the request object
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
 	Class<T> getInputClass();
@@ -27,5 +30,5 @@ public interface ObjectProcessor<T, U> {
 	 * @return the response object
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
-	U process(T input, long socketId);
+	void process(T input, long socketId, ObjectWriteProxy writeProxy) throws IOException;
 }
\ No newline at end of file
diff --git a/src/main/java/envoy/server/data/Message.java b/src/main/java/envoy/server/data/Message.java
index 19e25a6..af7f612 100644
--- a/src/main/java/envoy/server/data/Message.java
+++ b/src/main/java/envoy/server/data/Message.java
@@ -4,6 +4,7 @@ import java.util.Date;
 
 import javax.persistence.Entity;
 import javax.persistence.Id;
+import javax.persistence.ManyToOne;
 import javax.persistence.NamedQueries;
 import javax.persistence.NamedQuery;
 import javax.persistence.Table;
@@ -28,8 +29,12 @@ import envoy.data.MessageBuilder;
 @Entity
 @Table(name = "messages")
 @NamedQueries(
-	{ @NamedQuery(query = "SELECT m FROM Message m WHERE m.recipient =:recipient AND m.state = 1", name = "getUnreadMessages"), @NamedQuery(
-		query = "SELECT m FROM Message m WHERE m.sender =:sender AND m.state = :state",
+	{ @NamedQuery(
+		query = "SELECT m FROM Message m WHERE m.recipient =:recipient AND m.status = envoy.data.Message$MessageStatus.SENT",
+		name = "getUnreadMessages"
+	),
+			@NamedQuery(
+				query = "SELECT m FROM Message m WHERE m.sender =:sender AND m.status = :status",
 		name = "find read messages"//TODO do we need this namedQuery?
 	), @NamedQuery(query = "SELECT m FROM Message m WHERE m.id = :messageId", name = "get message") }//TODO do we need this namedQuery?
 )
@@ -37,13 +42,22 @@ public class Message {
 
 	@Id
 	private long								id;
-	private User								sender, recipient;
+
+	@ManyToOne
+	private User sender;
+
+	@ManyToOne
+	private User recipient;
+
 	@Temporal(TemporalType.TIMESTAMP)
 	private Date								creationDate;
+
 	@Temporal(TemporalType.TIMESTAMP)
 	private Date								receivedDate;
+
 	@Temporal(TemporalType.TIMESTAMP)
 	private Date								readDate;
+
 	private envoy.data.Message.MessageStatus	status;
 	private String								text;
 	private byte[]								attachment;
diff --git a/src/main/java/envoy/server/data/User.java b/src/main/java/envoy/server/data/User.java
index e0de15f..40e25c7 100644
--- a/src/main/java/envoy/server/data/User.java
+++ b/src/main/java/envoy/server/data/User.java
@@ -3,6 +3,7 @@ package envoy.server.data;
 import java.util.Date;
 import java.util.List;
 
+import javax.persistence.ElementCollection;
 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
@@ -27,7 +28,7 @@ import javax.persistence.TemporalType;
  */
 @Entity
 @Table(name = "users")
-@NamedQuery(query = "SELECT u FROM DBUser u WHERE u.id = :id", name = "getUserById")
+@NamedQuery(query = "SELECT u FROM User u WHERE u.id = :id", name = "getUserById")
 public class User {
 
 	@Id
@@ -35,9 +36,12 @@ public class User {
 	private long						id;
 	private String						name;
 	private byte[]						passwordHash;
+
 	@Temporal(TemporalType.TIMESTAMP)
 	private Date						lastSeen;
 	private envoy.data.User.UserStatus	status;
+
+	@ElementCollection
 	private List<User>					contacts;
 
 	/**
diff --git a/src/main/java/envoy/server/net/ObjectMessageProcessor.java b/src/main/java/envoy/server/net/ObjectMessageProcessor.java
index 1bf707f..47dae57 100644
--- a/src/main/java/envoy/server/net/ObjectMessageProcessor.java
+++ b/src/main/java/envoy/server/net/ObjectMessageProcessor.java
@@ -1,10 +1,8 @@
 package envoy.server.net;
 
 import java.io.ByteArrayInputStream;
-import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.ObjectInputStream;
-import java.io.ObjectOutputStream;
 import java.util.Set;
 
 import com.jenkov.nioserver.IMessageProcessor;
@@ -25,7 +23,7 @@ import envoy.server.ObjectProcessor;
  */
 public class ObjectMessageProcessor implements IMessageProcessor {
 
-	private final Set<ObjectProcessor<?, ?>>	processors;
+	private final Set<ObjectProcessor<?>> processors;
 
 	/**
 	 * The constructor to set the {@link ObjectProcessor}s.
@@ -33,9 +31,7 @@ public class ObjectMessageProcessor implements IMessageProcessor {
 	 * @param processors the {@link ObjectProcessor} to set
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
-	public ObjectMessageProcessor(Set<ObjectProcessor<?, ?>> processors) {
-		this.processors			= processors;
-	}
+	public ObjectMessageProcessor(Set<ObjectProcessor<?>> processors) { this.processors = processors; }
 
 	@SuppressWarnings("unchecked")
 	@Override
@@ -45,25 +41,17 @@ public class ObjectMessageProcessor implements IMessageProcessor {
 			System.out.println("Read object: " + obj.toString());
 
 			// Process object
-			processors.stream().filter(p -> p.getInputClass().isInstance(obj)).forEach((@SuppressWarnings("rawtypes") ObjectProcessor p) -> {
-				Object responseObj = p.process(p.getInputClass().cast(obj), message.socketId);
-				if (responseObj != null) {
-					// Create message targeted at the client
-					Message response = writeProxy.getMessage();
-					response.socketId = message.socketId;
-
-					// Serialize object to byte array
-					ByteArrayOutputStream baos = new ByteArrayOutputStream();
-					try (ObjectOutputStream oout = new ObjectOutputStream(baos)) {
-						oout.writeObject(responseObj);
+			processors.stream()
+				.filter(p -> p.getInputClass().isInstance(obj))
+				.forEach((@SuppressWarnings(
+					"rawtypes"
+				) ObjectProcessor p) -> {
+					try {
+						p.process(p.getInputClass().cast(obj), message.socketId, new ObjectWriteProxy(writeProxy));
 					} catch (IOException e) {
 						e.printStackTrace();
 					}
-					byte[] objBytes = baos.toByteArray();
-					response.writeToMessage(objBytes);
-					writeProxy.enqueue(response);
-				}
-			});
+				});
 		} catch (IOException | ClassNotFoundException e) {
 			e.printStackTrace();
 		}
diff --git a/src/main/java/envoy/server/net/ObjectWriteProxy.java b/src/main/java/envoy/server/net/ObjectWriteProxy.java
new file mode 100644
index 0000000..b1dc337
--- /dev/null
+++ b/src/main/java/envoy/server/net/ObjectWriteProxy.java
@@ -0,0 +1,34 @@
+package envoy.server.net;
+
+import java.io.IOException;
+
+import com.jenkov.nioserver.Message;
+import com.jenkov.nioserver.WriteProxy;
+
+import envoy.util.SerializationUtils;
+
+/**
+ * Project: <strong>envoy-server-standalone</strong><br>
+ * File: <strong>ObjectWriteProxy.java</strong><br>
+ * Created: <strong>04.01.2020</strong><br>
+ * 
+ * @author Kai S. K. Engelbart
+ * @since Envoy Server Standalone v0.1-alpha
+ */
+public class ObjectWriteProxy {
+
+	private final WriteProxy writeProxy;
+
+	public ObjectWriteProxy(WriteProxy writeProxy) { this.writeProxy = writeProxy; }
+
+	public void write(long recipientSocketId, Object obj) throws IOException {
+		// Create message targeted at the client
+		Message response = writeProxy.getMessage();
+		response.socketId = recipientSocketId;
+
+		// Serialize object to byte array
+		byte[] objBytes = SerializationUtils.writeToByteArray(obj);
+		response.writeToMessage(objBytes);
+		writeProxy.enqueue(response);
+	}
+}
diff --git a/src/main/resources/META-INF/persistence.xml b/src/main/resources/META-INF/persistence.xml
new file mode 100644
index 0000000..4d937c9
--- /dev/null
+++ b/src/main/resources/META-INF/persistence.xml
@@ -0,0 +1,29 @@
+<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
+             http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"
+	version="2.1">
+
+	<persistence-unit name="envoy"
+		transaction-type="RESOURCE_LOCAL">
+
+		<properties>
+			<property name="javax.persistence.jdbc.driver"
+				value="org.postgresql.Driver" /> <!-- DB Driver -->
+			<property name="javax.persistence.jdbc.url"
+				value="jdbc:postgresql://localhost/envoy" /> <!-- BD Mane -->
+			<property name="javax.persistence.jdbc.user" value="envoy" /> <!-- DB User -->
+			<property name="javax.persistence.jdbc.password"
+				value="envoy" /> <!-- DB Password -->
+
+			<property name="hibernate.dialect"
+				value="org.hibernate.dialect.PostgreSQL95Dialect" /> <!-- DB Dialect -->
+			<property name="hibernate.hbm2ddl.auto" value="update" /> <!-- create / create-drop / update -->
+
+			<property name="hibernate.show_sql" value="true" /> <!-- Show SQL in console -->
+			<property name="hibernate.format_sql" value="true" /> <!-- Show SQL formatted -->
+		</properties>
+
+	</persistence-unit>
+
+</persistence>
\ No newline at end of file

From d40194b10d94cce62695e9a1bace529e258f8fe3 Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Mon, 6 Jan 2020 17:40:19 +0100
Subject: [PATCH 4/7] LV-encoding messages, added JPA validation.

---
 .classpath                                       | 16 +++++-----------
 .project                                         | 11 +++++++++++
 .settings/org.eclipse.jdt.core.prefs             |  3 +++
 .settings/org.eclipse.jpt.core.prefs             |  3 +++
 ...lipse.wst.common.project.facet.core.prefs.xml |  7 +++++++
 ...org.eclipse.wst.common.project.facet.core.xml |  5 +++++
 src/main/java/envoy/server/Startup.java          |  4 ++--
 .../envoy/server/net/ObjectMessageReader.java    | 14 ++++----------
 .../java/envoy/server/net/ObjectWriteProxy.java  |  7 ++++++-
 9 files changed, 46 insertions(+), 24 deletions(-)
 create mode 100644 .settings/org.eclipse.jpt.core.prefs
 create mode 100644 .settings/org.eclipse.wst.common.project.facet.core.prefs.xml
 create mode 100644 .settings/org.eclipse.wst.common.project.facet.core.xml

diff --git a/.classpath b/.classpath
index 2a83b68..047eee0 100644
--- a/.classpath
+++ b/.classpath
@@ -6,11 +6,6 @@
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
-		<attributes>
-			<attribute name="maven.pomderived" value="true"/>
-		</attributes>
-	</classpathentry>
 	<classpathentry kind="src" output="target/test-classes" path="src/test/java">
 		<attributes>
 			<attribute name="optional" value="true"/>
@@ -18,12 +13,6 @@
 			<attribute name="test" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry excluding="**" kind="src" output="target/test-classes" path="src/test/resources">
-		<attributes>
-			<attribute name="maven.pomderived" value="true"/>
-			<attribute name="test" value="true"/>
-		</attributes>
-	</classpathentry>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8">
 		<attributes>
 			<attribute name="maven.pomderived" value="true"/>
@@ -35,5 +24,10 @@
 		</attributes>
 	</classpathentry>
 	<classpathentry kind="src" path="/envoy-common"/>
+	<classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
 	<classpathentry kind="output" path="target/classes"/>
 </classpath>
diff --git a/.project b/.project
index 45a395e..fdd0c87 100644
--- a/.project
+++ b/.project
@@ -5,11 +5,21 @@
 	<projects>
 	</projects>
 	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.wst.common.project.facet.core.builder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
 		<buildCommand>
 			<name>org.eclipse.jdt.core.javabuilder</name>
 			<arguments>
 			</arguments>
 		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.wst.validation.validationbuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
 		<buildCommand>
 			<name>org.eclipse.m2e.core.maven2Builder</name>
 			<arguments>
@@ -19,5 +29,6 @@
 	<natures>
 		<nature>org.eclipse.jdt.core.javanature</nature>
 		<nature>org.eclipse.m2e.core.maven2Nature</nature>
+		<nature>org.eclipse.wst.common.project.facet.core.nature</nature>
 	</natures>
 </projectDescription>
diff --git a/.settings/org.eclipse.jdt.core.prefs b/.settings/org.eclipse.jdt.core.prefs
index 2f5cc74..cac0df4 100644
--- a/.settings/org.eclipse.jdt.core.prefs
+++ b/.settings/org.eclipse.jdt.core.prefs
@@ -1,7 +1,10 @@
 eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
 org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
 org.eclipse.jdt.core.compiler.compliance=1.8
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
 org.eclipse.jdt.core.compiler.problem.enablePreviewFeatures=disabled
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
 org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
 org.eclipse.jdt.core.compiler.problem.reportPreviewFeatures=ignore
 org.eclipse.jdt.core.compiler.release=disabled
diff --git a/.settings/org.eclipse.jpt.core.prefs b/.settings/org.eclipse.jpt.core.prefs
new file mode 100644
index 0000000..7ff3376
--- /dev/null
+++ b/.settings/org.eclipse.jpt.core.prefs
@@ -0,0 +1,3 @@
+eclipse.preferences.version=1
+org.eclipse.jpt.core.platform=generic2_1
+org.eclipse.jpt.jpa.core.discoverAnnotatedClasses=true
diff --git a/.settings/org.eclipse.wst.common.project.facet.core.prefs.xml b/.settings/org.eclipse.wst.common.project.facet.core.prefs.xml
new file mode 100644
index 0000000..7961132
--- /dev/null
+++ b/.settings/org.eclipse.wst.common.project.facet.core.prefs.xml
@@ -0,0 +1,7 @@
+<root>
+  <facet id="jpt.jpa">
+    <node name="libprov">
+      <attribute name="provider-id" value="jpa-no-op-library-provider"/>
+    </node>
+  </facet>
+</root>
diff --git a/.settings/org.eclipse.wst.common.project.facet.core.xml b/.settings/org.eclipse.wst.common.project.facet.core.xml
new file mode 100644
index 0000000..90f3be6
--- /dev/null
+++ b/.settings/org.eclipse.wst.common.project.facet.core.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<faceted-project>
+  <installed facet="java" version="1.8"/>
+  <installed facet="jpt.jpa" version="2.1"/>
+</faceted-project>
diff --git a/src/main/java/envoy/server/Startup.java b/src/main/java/envoy/server/Startup.java
index b616946..58931ff 100644
--- a/src/main/java/envoy/server/Startup.java
+++ b/src/main/java/envoy/server/Startup.java
@@ -29,10 +29,10 @@ public class Startup {
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
 	public static void main(String[] args) throws IOException {
-		Set<ObjectProcessor<?, ?>> processors = new HashSet<>();
+		Set<ObjectProcessor<?>> processors = new HashSet<>();
 		processors.add(new LoginCredentialProcessor());
 		processors.add(new MessageProcessor());
-
+		// new PersistenceManager();
 		Server server = new Server(8080, () -> new ObjectMessageReader(), new ObjectMessageProcessor(processors));
 		server.start();
 		server.getSocketProcessor().registerSocketIdListener(ConnectionManager.getInstance());
diff --git a/src/main/java/envoy/server/net/ObjectMessageReader.java b/src/main/java/envoy/server/net/ObjectMessageReader.java
index b477734..51fa3df 100644
--- a/src/main/java/envoy/server/net/ObjectMessageReader.java
+++ b/src/main/java/envoy/server/net/ObjectMessageReader.java
@@ -5,10 +5,9 @@ import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 
-import com.jenkov.nioserver.IMessageReader;
-import com.jenkov.nioserver.Message;
-import com.jenkov.nioserver.MessageBuffer;
-import com.jenkov.nioserver.Socket;
+import com.jenkov.nioserver.*;
+
+import envoy.util.SerializationUtils;
 
 /**
  * This {@link IMessageReader} decodes serialized Java objects.<br>
@@ -49,7 +48,7 @@ public class ObjectMessageReader implements IMessageReader {
 
 		// Get message length
 		if (nextMessage.length - nextMessage.offset < 4) return;
-		int length = fromByteArray(nextMessage.sharedArray, nextMessage.offset) + 4;
+		int length = SerializationUtils.bytesToInt(nextMessage.sharedArray, nextMessage.offset) + 4;
 
 		if (nextMessage.length - nextMessage.offset >= length) {
 			Message message = messageBuffer.getMessage();
@@ -60,9 +59,4 @@ public class ObjectMessageReader implements IMessageReader {
 
 		buffer.clear();
 	}
-
-	private int fromByteArray(byte[] bytes, int offset) {
-		return ((bytes[offset] & 0xFF) << 24) | ((bytes[offset + 1] & 0xFF) << 16) | ((bytes[offset + 2] & 0xFF) << 8)
-				| ((bytes[offset + 3] & 0xFF) << 0);
-	}
 }
\ No newline at end of file
diff --git a/src/main/java/envoy/server/net/ObjectWriteProxy.java b/src/main/java/envoy/server/net/ObjectWriteProxy.java
index b1dc337..bd6baf4 100644
--- a/src/main/java/envoy/server/net/ObjectWriteProxy.java
+++ b/src/main/java/envoy/server/net/ObjectWriteProxy.java
@@ -11,7 +11,7 @@ import envoy.util.SerializationUtils;
  * Project: <strong>envoy-server-standalone</strong><br>
  * File: <strong>ObjectWriteProxy.java</strong><br>
  * Created: <strong>04.01.2020</strong><br>
- * 
+ *
  * @author Kai S. K. Engelbart
  * @since Envoy Server Standalone v0.1-alpha
  */
@@ -28,6 +28,11 @@ public class ObjectWriteProxy {
 
 		// Serialize object to byte array
 		byte[] objBytes = SerializationUtils.writeToByteArray(obj);
+
+		// Acquire object length in bytes
+		byte[] objLen = SerializationUtils.intToBytes(objBytes.length);
+
+		response.writeToMessage(objLen);
 		response.writeToMessage(objBytes);
 		writeProxy.enqueue(response);
 	}

From 786150ec0cadbbb36c6a14234d8c89a46cadea4e Mon Sep 17 00:00:00 2001
From: delvh <dev.lh@web.de>
Date: Sat, 11 Jan 2020 09:42:02 +0100
Subject: [PATCH 5/7] configured JPA validation

---
 .settings/org.eclipse.jpt.core.prefs          | 2 +-
 .settings/org.hibernate.eclipse.console.prefs | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)
 create mode 100644 .settings/org.hibernate.eclipse.console.prefs

diff --git a/.settings/org.eclipse.jpt.core.prefs b/.settings/org.eclipse.jpt.core.prefs
index 7ff3376..8aa2bb2 100644
--- a/.settings/org.eclipse.jpt.core.prefs
+++ b/.settings/org.eclipse.jpt.core.prefs
@@ -1,3 +1,3 @@
 eclipse.preferences.version=1
-org.eclipse.jpt.core.platform=generic2_1
+org.eclipse.jpt.core.platform=hibernate2_1
 org.eclipse.jpt.jpa.core.discoverAnnotatedClasses=true
diff --git a/.settings/org.hibernate.eclipse.console.prefs b/.settings/org.hibernate.eclipse.console.prefs
new file mode 100644
index 0000000..a6ccf3c
--- /dev/null
+++ b/.settings/org.hibernate.eclipse.console.prefs
@@ -0,0 +1,3 @@
+default.configuration=envoy-server-standalone
+eclipse.preferences.version=1
+hibernate3.enabled=true

From 135ca4a86f82cc5f98fb90a444946af417d6e20c Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Sat, 11 Jan 2020 11:43:31 +0100
Subject: [PATCH 6/7] Replaces local dependencies with jitpack.io dependencies

---
 .classpath |  6 ++++++
 pom.xml    | 15 +++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/.classpath b/.classpath
index 047eee0..b468bc4 100644
--- a/.classpath
+++ b/.classpath
@@ -29,5 +29,11 @@
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>
 	</classpathentry>
+	<classpathentry excluding="**" kind="src" output="target/test-classes" path="src/test/resources">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="test" value="true"/>
+		</attributes>
+	</classpathentry>
 	<classpathentry kind="output" path="target/classes"/>
 </classpath>
diff --git a/pom.xml b/pom.xml
index 48a6be0..c0ed70b 100644
--- a/pom.xml
+++ b/pom.xml
@@ -17,16 +17,23 @@
 		<maven.compiler.target>1.8</maven.compiler.target>
 	</properties>
 
+	<repositories>
+		<repository>
+			<id>jitpack.io</id>
+			<url>https://jitpack.io</url>
+		</repository>
+	</repositories>
+
 	<dependencies>
 		<dependency>
-			<groupId>informatik-ag-ngl</groupId>
+			<groupId>com.github.informatik-ag-ngl</groupId>
 			<artifactId>envoy-common</artifactId>
-			<version>0.2-alpha</version>
+			<version>develop-SNAPSHOT</version><!-- <version>0.2-alpha</version> -->
 		</dependency>
 		<dependency>
-			<groupId>informatik-ag-ngl</groupId>
+			<groupId>com.github.informatik-ag-ngl</groupId>
 			<artifactId>java-nio-server</artifactId>
-			<version>0.0.1-SNAPSHOT</version>
+			<version>master-SNAPSHOT</version>
 		</dependency>
 		<dependency>
 			<groupId>org.hibernate</groupId>

From fb4ecaed4e92992d8c9c2440bf2af4b740131caf Mon Sep 17 00:00:00 2001
From: delvh <dev.lh@web.de>
Date: Sat, 11 Jan 2020 18:28:48 +0100
Subject: [PATCH 7/7] Added EventProcessor and methods to handle MessageStatus
 changes

additionally cleaned up whole project, fixed some Javadoc errors and
added a few database and connection options.

Sorry for the huge commit, there was almost no time inbetween where a
commit would have been possible, as to solve every problem, a new
problem arose.
However, as of now, f/message_handling should be ready to be merged into
develop, besides that it could not be tested yet.
---
 .settings/org.eclipse.jdt.core.prefs          |  4 +
 .../java/envoy/server/ConnectionManager.java  | 16 ++--
 .../java/envoy/server/MessageProcessor.java   | 32 --------
 .../java/envoy/server/ObjectProcessor.java    |  7 +-
 src/main/java/envoy/server/Startup.java       |  4 +
 src/main/java/envoy/server/data/Message.java  | 29 ++++---
 src/main/java/envoy/server/data/User.java     | 34 +++++++-
 .../server/database/PersistenceManager.java   | 28 ++++++-
 .../server/net/ObjectMessageProcessor.java    | 18 ++---
 .../envoy/server/net/ObjectWriteProxy.java    | 14 ++++
 .../server/processors/EventProcessor.java     | 77 +++++++++++++++++++
 .../LoginCredentialProcessor.java             | 17 +++-
 .../server/processors/MessageProcessor.java   | 47 +++++++++++
 13 files changed, 255 insertions(+), 72 deletions(-)
 delete mode 100644 src/main/java/envoy/server/MessageProcessor.java
 create mode 100644 src/main/java/envoy/server/processors/EventProcessor.java
 rename src/main/java/envoy/server/{ => processors}/LoginCredentialProcessor.java (66%)
 create mode 100644 src/main/java/envoy/server/processors/MessageProcessor.java

diff --git a/.settings/org.eclipse.jdt.core.prefs b/.settings/org.eclipse.jdt.core.prefs
index cac0df4..db24ee7 100644
--- a/.settings/org.eclipse.jdt.core.prefs
+++ b/.settings/org.eclipse.jdt.core.prefs
@@ -1,7 +1,11 @@
 eclipse.preferences.version=1
 org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
 org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
+org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
 org.eclipse.jdt.core.compiler.compliance=1.8
+org.eclipse.jdt.core.compiler.debug.lineNumber=generate
+org.eclipse.jdt.core.compiler.debug.localVariable=generate
+org.eclipse.jdt.core.compiler.debug.sourceFile=generate
 org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
 org.eclipse.jdt.core.compiler.problem.enablePreviewFeatures=disabled
 org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
diff --git a/src/main/java/envoy/server/ConnectionManager.java b/src/main/java/envoy/server/ConnectionManager.java
index ac4b0c0..0ae8fcc 100644
--- a/src/main/java/envoy/server/ConnectionManager.java
+++ b/src/main/java/envoy/server/ConnectionManager.java
@@ -11,7 +11,7 @@ import com.jenkov.nioserver.ISocketIdListener;
  * Project: <strong>envoy-server-standalone</strong><br>
  * File: <strong>ConnectionManager.java</strong><br>
  * Created: <strong>03.01.2020</strong><br>
- * 
+ *
  * @author Kai S. K. Engelbart
  * @since Envoy Server Standalone v0.1-alpha
  */
@@ -20,14 +20,14 @@ public class ConnectionManager implements ISocketIdListener {
 	/**
 	 * Contains all socket IDs that have not yet performed a handshake / acquired
 	 * their corresponding user ID.
-	 * 
+	 *
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
 	private Set<Long> pendingSockets = new HashSet<>();
 
 	/**
 	 * Contains all socket IDs that have acquired a user ID as keys to these IDs.
-	 * 
+	 *
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
 	private Map<Long, Long> sockets = new HashMap<>();
@@ -53,14 +53,14 @@ public class ConnectionManager implements ISocketIdListener {
 
 	/**
 	 * Associates a socket ID with a user ID.
-	 * 
-	 * @param socketId the socket ID
+	 *
 	 * @param userId   the user ID
+	 * @param socketId the socket ID
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
-	public void registerUser(long socketId, long userId) {
-		sockets.put(socketId, userId);
-		pendingSockets.remove(socketId);
+	public void registerUser(long userId, long socketId) {
+		sockets.put(userId, socketId);
+		pendingSockets.remove(userId);
 	}
 
 	/**
diff --git a/src/main/java/envoy/server/MessageProcessor.java b/src/main/java/envoy/server/MessageProcessor.java
deleted file mode 100644
index 3e2f139..0000000
--- a/src/main/java/envoy/server/MessageProcessor.java
+++ /dev/null
@@ -1,32 +0,0 @@
-package envoy.server;
-
-import envoy.data.Message;
-import envoy.server.net.ObjectWriteProxy;
-
-/**
- * This {@link ObjectProcessor} handles incoming {@link Message}s.<br>
- * <br>
- * Project: <strong>envoy-server-standalone</strong><br>
- * File: <strong>MessageProcessor.java</strong><br>
- * Created: <strong>30.12.2019</strong><br>
- *
- * @author Kai S. K. Engelbart
- * @since Envoy Server Standalone v0.1-alpha
- */
-public class MessageProcessor implements ObjectProcessor<Message> {
-
-	@Override
-	public Class<Message> getInputClass() { return Message.class; }
-
-	@Override
-	public void process(Message message, long socketId, ObjectWriteProxy writeProxy) {
-
-		// TODO: Send message to recipient if online
-		ConnectionManager connectionManager = ConnectionManager.getInstance();
-		if (connectionManager.isOnline(message.getRecipientId())) {
-
-		}
-
-		// TODO: Add message to database
-	}
-}
diff --git a/src/main/java/envoy/server/ObjectProcessor.java b/src/main/java/envoy/server/ObjectProcessor.java
index 0221fc0..6828598 100644
--- a/src/main/java/envoy/server/ObjectProcessor.java
+++ b/src/main/java/envoy/server/ObjectProcessor.java
@@ -25,9 +25,10 @@ public interface ObjectProcessor<T> {
 	Class<T> getInputClass();
 
 	/**
-	 * @param input    the request object
-	 * @param socketId the ID of the socket from which the object was received
-	 * @return the response object
+	 * @param input      the request object
+	 * @param socketId   the ID of the socket from which the object was received
+	 * @param writeProxy the object that allows writing to a client
+	 * @throws IOException if something went wrong during processing
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
 	void process(T input, long socketId, ObjectWriteProxy writeProxy) throws IOException;
diff --git a/src/main/java/envoy/server/Startup.java b/src/main/java/envoy/server/Startup.java
index 58931ff..e2edb6a 100644
--- a/src/main/java/envoy/server/Startup.java
+++ b/src/main/java/envoy/server/Startup.java
@@ -8,6 +8,9 @@ import com.jenkov.nioserver.Server;
 
 import envoy.server.net.ObjectMessageProcessor;
 import envoy.server.net.ObjectMessageReader;
+import envoy.server.processors.EventProcessor;
+import envoy.server.processors.LoginCredentialProcessor;
+import envoy.server.processors.MessageProcessor;
 
 /**
  * Starts the server.<br>
@@ -32,6 +35,7 @@ public class Startup {
 		Set<ObjectProcessor<?>> processors = new HashSet<>();
 		processors.add(new LoginCredentialProcessor());
 		processors.add(new MessageProcessor());
+		processors.add(new EventProcessor());
 		// new PersistenceManager();
 		Server server = new Server(8080, () -> new ObjectMessageReader(), new ObjectMessageProcessor(processors));
 		server.start();
diff --git a/src/main/java/envoy/server/data/Message.java b/src/main/java/envoy/server/data/Message.java
index af7f612..575da6a 100644
--- a/src/main/java/envoy/server/data/Message.java
+++ b/src/main/java/envoy/server/data/Message.java
@@ -12,6 +12,7 @@ import javax.persistence.Temporal;
 import javax.persistence.TemporalType;
 
 import envoy.data.MessageBuilder;
+import envoy.server.database.PersistenceManager;
 
 /**
  * This class serves as a way to let Hibernate communicate with the server
@@ -32,16 +33,15 @@ import envoy.data.MessageBuilder;
 	{ @NamedQuery(
 		query = "SELECT m FROM Message m WHERE m.recipient =:recipient AND m.status = envoy.data.Message$MessageStatus.SENT",
 		name = "getUnreadMessages"
-	),
-			@NamedQuery(
-				query = "SELECT m FROM Message m WHERE m.sender =:sender AND m.status = :status",
-		name = "find read messages"//TODO do we need this namedQuery?
-	), @NamedQuery(query = "SELECT m FROM Message m WHERE m.id = :messageId", name = "get message") }//TODO do we need this namedQuery?
+	), @NamedQuery(
+		query = "SELECT m FROM Message m WHERE m.sender =:sender AND m.status = :status",
+		name = "find read messages"// TODO do we need this namedQuery?
+	), @NamedQuery(query = "SELECT m FROM Message m WHERE m.id = :messageId", name = "getMessageById") }
 )
 public class Message {
 
 	@Id
-	private long								id;
+	private long id;
 
 	@ManyToOne
 	private User sender;
@@ -50,13 +50,13 @@ public class Message {
 	private User recipient;
 
 	@Temporal(TemporalType.TIMESTAMP)
-	private Date								creationDate;
+	private Date creationDate;
 
 	@Temporal(TemporalType.TIMESTAMP)
-	private Date								receivedDate;
+	private Date receivedDate;
 
 	@Temporal(TemporalType.TIMESTAMP)
-	private Date								readDate;
+	private Date readDate;
 
 	private envoy.data.Message.MessageStatus	status;
 	private String								text;
@@ -76,9 +76,14 @@ public class Message {
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
 	public Message(envoy.data.Message message) {
-		id		= message.getId();
-		status	= message.getStatus();
-		text	= message.getText();
+		PersistenceManager persMan = PersistenceManager.getPersistenceManager();
+		id				= message.getId();
+		status			= message.getStatus();
+		text			= message.getText();
+		creationDate	= message.getCreationDate();
+		sender			= persMan.getUserById(message.getSenderId());
+		recipient		= persMan.getUserById(message.getRecipientId());
+		// attachment = message.getAttachment().toByteArray();DOES NOT WORK YET
 	}
 
 	/**
diff --git a/src/main/java/envoy/server/data/User.java b/src/main/java/envoy/server/data/User.java
index 40e25c7..5f4e28e 100644
--- a/src/main/java/envoy/server/data/User.java
+++ b/src/main/java/envoy/server/data/User.java
@@ -33,16 +33,42 @@ public class User {
 
 	@Id
 	@GeneratedValue(strategy = GenerationType.IDENTITY)
-	private long						id;
-	private String						name;
-	private byte[]						passwordHash;
+	private long	id;
+	private String	name;
+	private byte[]	passwordHash;
 
 	@Temporal(TemporalType.TIMESTAMP)
 	private Date						lastSeen;
 	private envoy.data.User.UserStatus	status;
 
 	@ElementCollection
-	private List<User>					contacts;
+	private List<User> contacts;
+
+	/**
+	 * Creates an instance of @link{User}.
+	 * Solely used for JPA/ Hibernate
+	 *
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public User() {}
+
+	/**
+	 * Creates an instance of @link{User}.
+	 *
+	 * @param user the {@link envoy.data.User} to convert
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public User(envoy.data.User user) {
+		id		= user.getId();
+		name	= user.getName();
+		status	= user.getStatus();
+	}
+
+	/**
+	 * @return a database {@link User} converted into an {@link envoy.data.User}
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public envoy.data.User toCommonUser() { return new envoy.data.User(this.id, this.name); }
 
 	/**
 	 * @return the id of a {link envoy.data.User}
diff --git a/src/main/java/envoy/server/database/PersistenceManager.java b/src/main/java/envoy/server/database/PersistenceManager.java
index e7c2dc8..fb38a9e 100644
--- a/src/main/java/envoy/server/database/PersistenceManager.java
+++ b/src/main/java/envoy/server/database/PersistenceManager.java
@@ -20,6 +20,21 @@ import envoy.server.data.User;
  */
 public class PersistenceManager {
 
+	private static final PersistenceManager persistenceManager = new PersistenceManager();
+
+	/**
+	 * Creates the singleton instance of the @link{PersistenceManager}.
+	 *
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	private PersistenceManager() {}
+
+	/**
+	 * @return the {@link PersistenceManager} singleton
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public static PersistenceManager getPersistenceManager() { return persistenceManager; }
+
 	private EntityManager entityManager = Persistence.createEntityManagerFactory("envoy").createEntityManager();
 
 	/**
@@ -55,7 +70,7 @@ public class PersistenceManager {
 	public void updateMessage(Message message) { entityManager.unwrap(Session.class).merge(message); }
 
 	/**
-	 * Searches for a user with a specific id.
+	 * Searches for a {@link User} with a specific id.
 	 *
 	 * @param id - the id to search for
 	 * @return the user with the specified id
@@ -63,6 +78,17 @@ public class PersistenceManager {
 	 */
 	public User getUserById(long id) { return (User) entityManager.createNamedQuery("getUserById").setParameter("id", id).getSingleResult(); }
 
+	/**
+	 * Searches for a {@link Message} with a specific id.
+	 *
+	 * @param id - the id to search for
+	 * @return the message with the specified id
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public Message getMessageById(long id) {
+		return (Message) entityManager.createNamedQuery("getMessageById").setParameter("id", id).getSingleResult();
+	}
+
 	/**
 	 * Returns all messages received while being offline.
 	 *
diff --git a/src/main/java/envoy/server/net/ObjectMessageProcessor.java b/src/main/java/envoy/server/net/ObjectMessageProcessor.java
index 47dae57..226fb69 100644
--- a/src/main/java/envoy/server/net/ObjectMessageProcessor.java
+++ b/src/main/java/envoy/server/net/ObjectMessageProcessor.java
@@ -41,17 +41,13 @@ public class ObjectMessageProcessor implements IMessageProcessor {
 			System.out.println("Read object: " + obj.toString());
 
 			// Process object
-			processors.stream()
-				.filter(p -> p.getInputClass().isInstance(obj))
-				.forEach((@SuppressWarnings(
-					"rawtypes"
-				) ObjectProcessor p) -> {
-					try {
-						p.process(p.getInputClass().cast(obj), message.socketId, new ObjectWriteProxy(writeProxy));
-					} catch (IOException e) {
-						e.printStackTrace();
-					}
-				});
+			processors.stream().filter(p -> p.getInputClass().isInstance(obj)).forEach((@SuppressWarnings("rawtypes") ObjectProcessor p) -> {
+				try {
+					p.process(p.getInputClass().cast(obj), message.socketId, new ObjectWriteProxy(writeProxy));
+				} catch (IOException e) {
+					e.printStackTrace();
+				}
+			});
 		} catch (IOException | ClassNotFoundException e) {
 			e.printStackTrace();
 		}
diff --git a/src/main/java/envoy/server/net/ObjectWriteProxy.java b/src/main/java/envoy/server/net/ObjectWriteProxy.java
index bd6baf4..2ec9223 100644
--- a/src/main/java/envoy/server/net/ObjectWriteProxy.java
+++ b/src/main/java/envoy/server/net/ObjectWriteProxy.java
@@ -8,6 +8,8 @@ import com.jenkov.nioserver.WriteProxy;
 import envoy.util.SerializationUtils;
 
 /**
+ * This class defines methods to send an object to a client.<br>
+ * <br>
  * Project: <strong>envoy-server-standalone</strong><br>
  * File: <strong>ObjectWriteProxy.java</strong><br>
  * Created: <strong>04.01.2020</strong><br>
@@ -19,8 +21,20 @@ public class ObjectWriteProxy {
 
 	private final WriteProxy writeProxy;
 
+	/**
+	 * Creates an instance of @link{ObjectWriteProxy}.
+	 *
+	 * @param writeProxy the {@link WriteProxy} to write objects to another client
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
 	public ObjectWriteProxy(WriteProxy writeProxy) { this.writeProxy = writeProxy; }
 
+	/**
+	 * @param recipientSocketId the socket id of the recipient
+	 * @param obj               the object to return to the client
+	 * @throws IOException if the serialization of the object failed
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
 	public void write(long recipientSocketId, Object obj) throws IOException {
 		// Create message targeted at the client
 		Message response = writeProxy.getMessage();
diff --git a/src/main/java/envoy/server/processors/EventProcessor.java b/src/main/java/envoy/server/processors/EventProcessor.java
new file mode 100644
index 0000000..58c769f
--- /dev/null
+++ b/src/main/java/envoy/server/processors/EventProcessor.java
@@ -0,0 +1,77 @@
+package envoy.server.processors;
+
+import java.io.IOException;
+
+import envoy.data.Message;
+import envoy.data.Message.MessageStatus;
+import envoy.event.Event;
+import envoy.event.MessageStatusChangeEvent;
+import envoy.exception.EnvoyException;
+import envoy.server.ConnectionManager;
+import envoy.server.ObjectProcessor;
+import envoy.server.database.PersistenceManager;
+import envoy.server.net.ObjectWriteProxy;
+
+/**
+ * Project: <strong>envoy-server-standalone</strong><br>
+ * File: <strong>EventProcessor.java</strong><br>
+ * Created: <strong>10 Jan 2020</strong><br>
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Server Standalone v0.1-alpha
+ */
+public class EventProcessor implements ObjectProcessor<Event<?>> {
+
+	private Event<?> event;
+
+	/**
+	 * Creates an instance of @link{EventProcessor}.
+	 *
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public EventProcessor() {}
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public Class<Event<?>> getInputClass() { return (Class<Event<?>>) event.getClass(); }
+
+	@Override
+	public void process(Event<?> input, long socketId, ObjectWriteProxy writeProxy) throws IOException {
+		event = input;
+		if (event instanceof MessageStatusChangeEvent) try {
+			applyMessageStatusChange((MessageStatusChangeEvent) event, writeProxy);
+		} catch (EnvoyException e) {
+			e.printStackTrace();
+		}
+	}
+
+	/**
+	 * Redirects messageStatus changes to the database and to the recipient of the
+	 * {@link Message}.
+	 *
+	 * @param event the {@link MessageStatusChangeEvent} to adjust
+	 * @throws EnvoyException if the {@link Message} has an invalid state
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	private void applyMessageStatusChange(MessageStatusChangeEvent event, ObjectWriteProxy writeProxy) throws EnvoyException {
+		if (!(event.get() == MessageStatus.READ))// check that no invalid MessageStatuses are sent
+			throw new EnvoyException("Message" + event.getId() + "has an invalid status");
+
+		ConnectionManager			conMan	= ConnectionManager.getInstance();
+		PersistenceManager			perMan	= PersistenceManager.getPersistenceManager();
+		envoy.server.data.Message	msg		= perMan.getMessageById(event.getId());
+
+		msg.setStatus(event.get());
+		msg.setReadDate(event.getDate());
+
+		if (conMan.isOnline(msg.getRecipient().getId())) try {
+			writeProxy.write(conMan.getSocketId(msg.getRecipient().getId()), event);
+		} catch (IOException e) {
+			System.err.println("Recipient online. Failed to send MessageStatusChangedEvent at message" + event.getId());
+			e.printStackTrace();
+		}
+		perMan.updateMessage(msg);
+
+	}
+
+}
diff --git a/src/main/java/envoy/server/LoginCredentialProcessor.java b/src/main/java/envoy/server/processors/LoginCredentialProcessor.java
similarity index 66%
rename from src/main/java/envoy/server/LoginCredentialProcessor.java
rename to src/main/java/envoy/server/processors/LoginCredentialProcessor.java
index 89261cf..e94ce91 100644
--- a/src/main/java/envoy/server/LoginCredentialProcessor.java
+++ b/src/main/java/envoy/server/processors/LoginCredentialProcessor.java
@@ -1,11 +1,18 @@
-package envoy.server;
+package envoy.server.processors;
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Date;
+import java.util.List;
 
 import envoy.data.Contacts;
 import envoy.data.LoginCredentials;
+import envoy.data.Message.MessageStatus;
 import envoy.data.User;
+import envoy.server.ConnectionManager;
+import envoy.server.ObjectProcessor;
+import envoy.server.data.Message;
+import envoy.server.database.PersistenceManager;
 import envoy.server.net.ObjectWriteProxy;
 
 /**
@@ -42,5 +49,13 @@ public class LoginCredentialProcessor implements ObjectProcessor<LoginCredential
 		writeProxy.write(socketId, user);
 		System.out.println("Sending contacts...");
 		writeProxy.write(socketId, contacts);
+		System.out.println("Sending unread messages and updating them in the database...");
+		List<Message> pendingMessages = PersistenceManager.getPersistenceManager().getUnreadMessages(new envoy.server.data.User(user));
+		pendingMessages.forEach((msg) -> {
+			msg.setReceivedDate(new Date());
+			msg.setStatus(MessageStatus.RECEIVED);
+			PersistenceManager.getPersistenceManager().updateMessage(msg);
+		});
+		writeProxy.write(socketId, pendingMessages);
 	}
 }
diff --git a/src/main/java/envoy/server/processors/MessageProcessor.java b/src/main/java/envoy/server/processors/MessageProcessor.java
new file mode 100644
index 0000000..ce857de
--- /dev/null
+++ b/src/main/java/envoy/server/processors/MessageProcessor.java
@@ -0,0 +1,47 @@
+package envoy.server.processors;
+
+import java.io.IOException;
+import java.util.Date;
+
+import envoy.data.Message;
+import envoy.event.MessageStatusChangeEvent;
+import envoy.server.ConnectionManager;
+import envoy.server.ObjectProcessor;
+import envoy.server.database.PersistenceManager;
+import envoy.server.net.ObjectWriteProxy;
+
+/**
+ * This {@link ObjectProcessor} handles incoming {@link Message}s.<br>
+ * <br>
+ * Project: <strong>envoy-server-standalone</strong><br>
+ * File: <strong>MessageProcessor.java</strong><br>
+ * Created: <strong>30.12.2019</strong><br>
+ *
+ * @author Kai S. K. Engelbart
+ * @since Envoy Server Standalone v0.1-alpha
+ */
+public class MessageProcessor implements ObjectProcessor<Message> {
+
+	@Override
+	public Class<Message> getInputClass() { return Message.class; }
+
+	@Override
+	public void process(Message message, long socketId, ObjectWriteProxy writeProxy) {
+
+		ConnectionManager connectionManager = ConnectionManager.getInstance();
+		message.nextStatus();
+		if (connectionManager.isOnline(message.getRecipientId())) try {// if recipient is online, he receives the message directly
+			writeProxy.write(connectionManager.getSocketId(message.getRecipientId()), message);
+		} catch (IOException e) {
+			System.err.println("Recipient online. Failed to send message" + message.getId());
+			e.printStackTrace();
+		}
+		try {// sender receives confirmation that the server received the message
+			writeProxy.write(connectionManager.getSocketId(message.getSenderId()),
+					new MessageStatusChangeEvent(message.getId(), message.getStatus(), new Date()));
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+		PersistenceManager.getPersistenceManager().addMessage(new envoy.server.data.Message(message));
+	}
+}