diff --git a/src/io/github/norbipeti/chat/server/Main.java b/src/io/github/norbipeti/chat/server/Main.java
index 4fca01c..68ad7c2 100644
--- a/src/io/github/norbipeti/chat/server/Main.java
+++ b/src/io/github/norbipeti/chat/server/Main.java
@@ -35,11 +35,10 @@ public class Main {
 				user.setName("asd");
 				user.setEmail("test@test.com");
 				User user2 = new User();
-				user2.setName("Teszt"); // TODO:
-										// http://www.journaldev.com/3524/spring-hibernate-integration-example-tutorial
+				user2.setName("Teszt");
 				user2.setEmail("test2@test.com");
-				user = provider.save(user);
-				user2 = provider.save(user2);
+				// user = provider.save(user);
+				// user2 = provider.save(user2);
 				user.getContacts().add(user2);
 				user2.getContacts().add(user);
 				LogManager.getLogger().log(Level.DEBUG, "1st's contact: " + user.getContacts().get(0));
@@ -50,7 +49,9 @@ public class Main {
 				user.getConversations().add(conversation);
 				LogManager.getLogger().debug("User: " + user);
 				conversation.getUsers().add(user2);
-				LogManager.getLogger().debug("User2: " + user2);
+				LogManager.getLogger().debug("User2: " + user2); // TODO: Switch
+																	// to JSON
+																	// files?
 				user2.getConversations().add(conversation); // TODO: Fix
 															// duplicate
 				// key constraint
diff --git a/src/io/github/norbipeti/chat/server/db/domain/ChatDatabaseEntity.java b/src/io/github/norbipeti/chat/server/db/domain/ChatDatabaseEntity.java
index 56af04a..21f0085 100644
--- a/src/io/github/norbipeti/chat/server/db/domain/ChatDatabaseEntity.java
+++ b/src/io/github/norbipeti/chat/server/db/domain/ChatDatabaseEntity.java
@@ -1,5 +1,8 @@
 package io.github.norbipeti.chat.server.db.domain;
 
-public abstract class ChatDatabaseEntity {
+import java.io.Serializable;
+
+@SuppressWarnings("serial")
+public abstract class ChatDatabaseEntity implements Serializable {
 
 }
diff --git a/src/io/github/norbipeti/chat/server/db/domain/Conversation.java b/src/io/github/norbipeti/chat/server/db/domain/Conversation.java
index 7c44ab3..1129ccc 100644
--- a/src/io/github/norbipeti/chat/server/db/domain/Conversation.java
+++ b/src/io/github/norbipeti/chat/server/db/domain/Conversation.java
@@ -9,6 +9,7 @@ import javax.persistence.*;
 
 @Entity
 public class Conversation extends ChatDatabaseEntity {
+	private static final long serialVersionUID = 5058682475353799722L;
 	@Id
 	@GeneratedValue(strategy = GenerationType.IDENTITY)
 	@Column(name = "id", unique = true, nullable = false)
diff --git a/src/io/github/norbipeti/chat/server/db/domain/Message.java b/src/io/github/norbipeti/chat/server/db/domain/Message.java
index 84a5650..9d23dde 100644
--- a/src/io/github/norbipeti/chat/server/db/domain/Message.java
+++ b/src/io/github/norbipeti/chat/server/db/domain/Message.java
@@ -6,11 +6,12 @@ import javax.persistence.*;
 
 @Entity
 public class Message extends ChatDatabaseEntity {
+	private static final long serialVersionUID = 6345941601716826570L;
 	@Id
 	@GeneratedValue(strategy = GenerationType.IDENTITY)
 	@Column(name = "id", unique = true, nullable = false)
 	private Long id;
-	@ManyToOne
+	@ManyToOne(cascade = CascadeType.PERSIST, fetch = FetchType.EAGER)
 	// @JoinTable(name="user_message")
 	private User sender;
 	private Date time;
diff --git a/src/io/github/norbipeti/chat/server/db/domain/User.java b/src/io/github/norbipeti/chat/server/db/domain/User.java
index 81be3eb..292cc69 100644
--- a/src/io/github/norbipeti/chat/server/db/domain/User.java
+++ b/src/io/github/norbipeti/chat/server/db/domain/User.java
@@ -10,6 +10,7 @@ import javax.persistence.*;
 @Entity
 @Table(name = "\"User\"")
 public class User extends ChatDatabaseEntity {
+	private static final long serialVersionUID = 2862762084164225666L;
 	@Id
 	@GeneratedValue(strategy = GenerationType.IDENTITY)
 	@Column(name = "id", unique = true, nullable = false)
@@ -26,7 +27,7 @@ public class User extends ChatDatabaseEntity {
 	private String sessionid;
 	@ElementCollection(fetch = FetchType.EAGER)
 	// @ManyToMany(fetch = FetchType.EAGER, mappedBy = "users")
-	@ManyToMany(mappedBy = "users", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
+	@ManyToMany(mappedBy = "users", fetch = FetchType.EAGER, cascade = CascadeType.MERGE)
 	// @ManyToMany(mappedBy = "users")
 	// @JoinTable(name = "User_Conversation", joinColumns =
 	// @JoinColumn(referencedColumnName = "id", unique = false),