revised exception handling for empty fields.

backend/src/main/java/com/vaessl/app/connection/ConnectionProvider.java

@@ -5,6 +5,8 @@ import com.vaessl.app.dto.ConnectionResponse;
 
 public interface ConnectionProvider {
 
+    void checkCredentials(ConnectionRequest request);
+
     String getServiceType();
 
     ConnectionResponse authenticate(ConnectionRequest request);

backend/src/main/java/com/vaessl/app/connection/ConnectionService.java

@@ -8,7 +8,6 @@ import org.springframework.stereotype.Service;
 
 import com.vaessl.app.dto.ConnectionRequest;
 import com.vaessl.app.dto.ConnectionResponse;
-import com.vaessl.app.exception.ProviderNotFoundException;
 
 @Service
 public class ConnectionService {
@@ -27,9 +26,7 @@ public class ConnectionService {
 
         ConnectionProvider provider = providerRegistry.get(request.serviceType());
 
-        if (provider == null) {
-            throw new ProviderNotFoundException();
-        }
+        provider.checkCredentials(request);
 
         ConnectionResponse response = provider.authenticate(request);
 

backend/src/main/java/com/vaessl/app/connection/HomeBoxConnectionProvider.java

@@ -1,7 +1,9 @@
 package com.vaessl.app.connection;
 
 import java.time.Instant;
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import org.springframework.stereotype.Component;
@@ -9,6 +11,7 @@ import org.springframework.web.client.RestClient;
 
 import com.vaessl.app.dto.ConnectionRequest;
 import com.vaessl.app.dto.ConnectionResponse;
+import com.vaessl.app.exception.EmptyCredentialsException;
 
 import static com.vaessl.app.connection.Endpoint.*;
 
@@ -24,6 +27,22 @@ public class HomeBoxConnectionProvider implements ConnectionProvider {
         this.cRepository = cRepository;
     }
 
+    @Override
+    public void checkCredentials(ConnectionRequest request) {
+        if (request.username() == null || request.password() == null) {
+            List<String> missingFields = new ArrayList<>();
+
+            if (request.username() == null) {
+                missingFields.add("username");
+            }
+            if (request.password() == null) {
+                missingFields.add("password");
+
+            }
+            throw new EmptyCredentialsException(List.copyOf(missingFields));
+        }
+    }
+
     @Override
     public String getServiceType() {
         return "HOMEBOX";