fix: fixed non-empty String validation to be non-empty

src/main/java/uulm/teamname/marvelous/gamelibrary/messages/ErrorMessage.java

@@ -1,5 +1,6 @@
 package uulm.teamname.marvelous.gamelibrary.messages;
 
+import jakarta.validation.constraints.NotEmpty;
 import jakarta.validation.constraints.NotNull;
 
 public class ErrorMessage extends BasicMessage{

src/main/java/uulm/teamname/marvelous/gamelibrary/messages/client/HelloServerMessage.java

@@ -1,5 +1,6 @@
 package uulm.teamname.marvelous.gamelibrary.messages.client;
 
+import jakarta.validation.constraints.NotEmpty;
 import uulm.teamname.marvelous.gamelibrary.messages.BasicMessage;
 import uulm.teamname.marvelous.gamelibrary.messages.MessageType;
 
@@ -10,10 +11,10 @@ public class HelloServerMessage extends BasicMessage {
     public final MessageType messageType = MessageType.HELLO_SERVER;
 
     /** User-chosen name, basically a PlayerName */
-    @NotNull
+    @NotEmpty
     public String name;
 
     /** Device ID sent by the Client, might be anything, but used together with name to uniquely identify the client */
-    @NotNull
+    @NotEmpty
     public String deviceID;
 }

src/main/java/uulm/teamname/marvelous/gamelibrary/messages/server/GoodbyeClientMessage.java

@@ -1,5 +1,6 @@
 package uulm.teamname.marvelous.gamelibrary.messages.server;
 
+import jakarta.validation.constraints.NotEmpty;
 import uulm.teamname.marvelous.gamelibrary.messages.BasicMessage;
 import uulm.teamname.marvelous.gamelibrary.messages.MessageType;
 
@@ -10,6 +11,6 @@ public class GoodbyeClientMessage extends BasicMessage {
     public final MessageType messageType = MessageType.GOODBYE_CLIENT;
 
     /** A message sent to the client on disconnect */
-    @NotNull
+    @NotEmpty
     public String message = "You got disconnected.";
 }