Merge pull request #10 from informatik-ag-ngl/f/message_processing

Implemented the processing of messages sent by clients

.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 +24,16 @@
 		</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 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>

.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>

.settings/org.eclipse.jdt.core.prefs

@@ -1,7 +1,14 @@
 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
 org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
 org.eclipse.jdt.core.compiler.problem.reportPreviewFeatures=ignore
 org.eclipse.jdt.core.compiler.release=disabled

.settings/org.eclipse.jpt.core.prefs

@@ -0,0 +1,3 @@
+eclipse.preferences.version=1
+org.eclipse.jpt.core.platform=hibernate2_1
+org.eclipse.jpt.jpa.core.discoverAnnotatedClasses=true

.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>

.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>

.settings/org.hibernate.eclipse.console.prefs

@@ -0,0 +1,3 @@
+default.configuration=envoy-server-standalone
+eclipse.preferences.version=1
+hibernate3.enabled=true

pom.xml

@@ -17,22 +17,34 @@
 		<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>
 			<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>

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 userId   the user ID
+	 * @param socketId the socket ID
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public void registerUser(long userId, long socketId) {
+		sockets.put(userId, socketId);
+		pendingSockets.remove(userId);
+	}
+
+	/**
+	 * @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); }
+}

src/main/java/envoy/server/LoginCredentialProcessor.java

@@ -1,29 +0,0 @@
-package envoy.server;
-
-import envoy.data.LoginCredentials;
-import envoy.data.User;
-
-/**
- * This {@link ObjectProcessor} handles {@link LoginCredentials}.<br>
- * <br>
- * Project: <strong>envoy-server-standalone</strong><br>
- * File: <strong>LoginCredentialProcessor.java</strong><br>
- * Created: <strong>30.12.2019</strong><br>
- *
- * @author Kai S. K. Engelbart
- * @since Envoy Server Standalone v0.1-alpha
- */
-public class LoginCredentialProcessor implements ObjectProcessor<LoginCredentials, User> {
-
-	// TODO: Acquire user IDs from database
-	private static long currentUserId = 1;
-
-	@Override
-	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());
-	}
-}

src/main/java/envoy/server/MessageProcessor.java

@@ -1,22 +0,0 @@
-package envoy.server;
-
-import envoy.data.Message;
-
-/**
- * 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, Void> {
-
-	@Override
-	public Class<Message> getInputClass() { return Message.class; }
-
-	@Override
-	public Void process(Message input) { return null; }
-}

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>
@@ -10,21 +14,22 @@ 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();
 
 	/**
 	 * @param input      the request object
-	 * @return the response 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
 	 */
-	U process(T input);
+	void process(T input, long socketId, ObjectWriteProxy writeProxy) throws IOException;
 }

src/main/java/envoy/server/Startup.java

@@ -6,6 +6,12 @@ import java.util.Set;
 
 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>
  * <br>
@@ -26,10 +32,13 @@ 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());
+		processors.add(new EventProcessor());
+		// new PersistenceManager();
 		Server server = new Server(8080, () -> new ObjectMessageReader(), new ObjectMessageProcessor(processors));
 		server.start();
+		server.getSocketProcessor().registerSocketIdListener(ConnectionManager.getInstance());
 	}
 }

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;
@@ -11,6 +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
@@ -28,22 +30,34 @@ 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(
+	{ @NamedQuery(
-		query = "SELECT m FROM Message m WHERE m.sender =:sender AND m.state = :state",
+		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.id = :messageId", name = "getMessageById") }
 )
 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;
@@ -62,9 +76,14 @@ public class Message {
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
 	public Message(envoy.data.Message message) {
+		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
 	}
 
 	/**

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
@@ -35,11 +36,40 @@ 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;
 
+	/**
+	 * 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}
 	 * @since Envoy Server Standalone v0.1-alpha

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.
 	 *

src/main/java/envoy/server/net/ObjectMessageProcessor.java

@@ -1,16 +1,16 @@
-package envoy.server;
+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;
 import com.jenkov.nioserver.Message;
 import com.jenkov.nioserver.WriteProxy;
 
+import envoy.server.ObjectProcessor;
+
 /**
  * Handles incoming objects.<br>
  * <br>
@@ -23,7 +23,7 @@ import com.jenkov.nioserver.WriteProxy;
  */
 public class ObjectMessageProcessor implements IMessageProcessor {
 
-	private final Set<ObjectProcessor<?, ?>> processors;
+	private final Set<ObjectProcessor<?>> processors;
 
 	/**
 	 * The constructor to set the {@link ObjectProcessor}s.
@@ -31,7 +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
@@ -42,23 +42,11 @@ 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));
+				try {
-				if (responseObj != null) {
+					p.process(p.getInputClass().cast(obj), message.socketId, new ObjectWriteProxy(writeProxy));
-					// 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);
 				} catch (IOException e) {
 					e.printStackTrace();
 				}
-					byte[] objBytes = baos.toByteArray();
-					response.writeToMessage(objBytes);
-					writeProxy.enqueue(response);
-				}
 			});
 		} catch (IOException | ClassNotFoundException e) {
 			e.printStackTrace();

src/main/java/envoy/server/net/ObjectMessageReader.java

@@ -1,14 +1,13 @@
-package envoy.server;
+package envoy.server.net;
 
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 
-import com.jenkov.nioserver.IMessageReader;
+import com.jenkov.nioserver.*;
-import com.jenkov.nioserver.Message;
+
-import com.jenkov.nioserver.MessageBuffer;
+import envoy.util.SerializationUtils;
-import com.jenkov.nioserver.Socket;
 
 /**
  * This {@link IMessageReader} decodes serialized Java objects.<br>
@@ -26,11 +25,6 @@ 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; }
 
@@ -54,7 +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();

src/main/java/envoy/server/net/ObjectWriteProxy.java

@@ -0,0 +1,53 @@
+package envoy.server.net;
+
+import java.io.IOException;
+
+import com.jenkov.nioserver.Message;
+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>
+ *
+ * @author Kai S. K. Engelbart
+ * @since Envoy Server Standalone v0.1-alpha
+ */
+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();
+		response.socketId = recipientSocketId;
+
+		// 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);
+	}
+}

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);
+
+	}
+
+}

src/main/java/envoy/server/processors/LoginCredentialProcessor.java

@@ -0,0 +1,61 @@
+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;
+
+/**
+ * This {@link ObjectProcessor} handles {@link LoginCredentials}.<br>
+ * <br>
+ * Project: <strong>envoy-server-standalone</strong><br>
+ * File: <strong>LoginCredentialProcessor.java</strong><br>
+ * Created: <strong>30.12.2019</strong><br>
+ *
+ * @author Kai S. K. Engelbart
+ * @since Envoy Server Standalone v0.1-alpha
+ */
+public class LoginCredentialProcessor implements ObjectProcessor<LoginCredentials> {
+
+	// TODO: Acquire user IDs from database
+	private static long currentUserId = 1;
+
+	@Override
+	public Class<LoginCredentials> getInputClass() { return LoginCredentials.class; }
+
+	@Override
+	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());
+
+		// 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);
+		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);
+	}
+}

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));
+	}
+}

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>