add exception classes, and DAO layer (#5)

make spotless

add exception handler

make spotless

resolve modelParameter

backend/src/main/java/com/llm_service/llm_service/controller/conversation/ConversationController.java

@@ -1,6 +1,6 @@
 package com.llm_service.llm_service.controller.conversation;
 
-import com.llm_service.llm_service.exception.conversation.ConversationNotFound;
+import com.llm_service.llm_service.exception.conversation.ConversationNotFoundException;
 import com.llm_service.llm_service.model.Conversation;
 import com.llm_service.llm_service.service.ConversationService;
 import java.util.UUID;
@@ -17,7 +17,8 @@ public class ConversationController {
     private final ConversationService conversationService;
 
     @GetMapping("/{id}")
-    public ResponseEntity<Conversation> getConversationById(@PathVariable UUID id) throws ConversationNotFound {
+    public ResponseEntity<Conversation> getConversationById(@PathVariable UUID id)
+            throws ConversationNotFoundException {
         Conversation conversation = conversationService.getByID(id);
 
         return ResponseEntity.status(HttpStatus.OK).body(conversation);
@@ -32,9 +33,16 @@ public ResponseEntity<Conversation> createConversation() {
 
     @PutMapping("/{id}/continue")
     public ResponseEntity<Conversation> continueConversation(
-            @PathVariable UUID id, @RequestBody ConversationRequest conversationRequest) throws ConversationNotFound {
+            @PathVariable UUID id, @RequestBody ConversationRequest conversationRequest)
+            throws ConversationNotFoundException {
         Conversation conversation = conversationService.update(id, conversationRequest);
 
         return ResponseEntity.status(HttpStatus.OK).body(conversation);
     }
+
+    @ExceptionHandler(ConversationNotFoundException.class)
+    public ResponseEntity<String> handleConversationNotFoundException(
+            ConversationNotFoundException conversationNotFoundException) {
+        return ResponseEntity.status(HttpStatus.NOT_FOUND).body(conversationNotFoundException.getMessage());
+    }
 }

backend/src/main/java/com/llm_service/llm_service/controller/conversation/ConversationControllerMapper.java

@@ -0,0 +1,9 @@
+package com.llm_service.llm_service.controller.conversation;
+
+import com.llm_service.llm_service.model.Conversation;
+import org.mapstruct.Mapper;
+
+@Mapper(componentModel = "spring")
+public interface ConversationControllerMapper {
+    ConversationResponse map(Conversation conversation);
+}

backend/src/main/java/com/llm_service/llm_service/controller/conversation/ConversationResponse.java

@@ -1,5 +1,6 @@
 package com.llm_service.llm_service.controller.conversation;
 
+import java.util.UUID;
 import lombok.Builder;
 import lombok.Value;
 import lombok.extern.jackson.Jacksonized;
@@ -8,5 +9,6 @@
 @Builder
 @Jacksonized
 public class ConversationResponse {
+    UUID id;
     String text;
 }

backend/src/main/java/com/llm_service/llm_service/exception/conversation/ConversationAlreadyExistsException.java

@@ -0,0 +1,9 @@
+package com.llm_service.llm_service.exception.conversation;
+
+import java.util.UUID;
+
+public class ConversationAlreadyExistsException extends Exception {
+    public ConversationAlreadyExistsException(UUID id) {
+        super("Conversation with id " + id + " already exists");
+    }
+}

backend/src/main/java/com/llm_service/llm_service/exception/conversation/ConversationNotFoundException.java

@@ -0,0 +1,9 @@
+package com.llm_service.llm_service.exception.conversation;
+
+import java.util.UUID;
+
+public class ConversationNotFoundException extends Exception {
+    public ConversationNotFoundException(UUID id) {
+        super("Conversation with id " + id + " is not found");
+    }
+}

backend/src/main/java/com/llm_service/llm_service/exception/user/UserAlreadyExistsException.java

@@ -0,0 +1,9 @@
+package com.llm_service.llm_service.exception.user;
+
+import java.util.UUID;
+
+public class UserAlreadyExistsException extends Exception {
+    public UserAlreadyExistsException(UUID id) {
+        super("User with id " + id + " already exists");
+    }
+}

backend/src/main/java/com/llm_service/llm_service/exception/user/UserNotFoundException.java

@@ -0,0 +1,9 @@
+package com.llm_service.llm_service.exception.user;
+
+import java.util.UUID;
+
+public class UserNotFoundException extends Exception {
+    public UserNotFoundException(UUID id) {
+        super("User with id " + id + " is not found");
+    }
+}

backend/src/main/java/com/llm_service/llm_service/service/ConversationService.java

@@ -1,7 +1,7 @@
 package com.llm_service.llm_service.service;
 
 import com.llm_service.llm_service.controller.conversation.ConversationRequest;
-import com.llm_service.llm_service.exception.conversation.ConversationNotFound;
+import com.llm_service.llm_service.exception.conversation.ConversationNotFoundException;
 import com.llm_service.llm_service.model.Conversation;
 import java.util.UUID;
 import lombok.RequiredArgsConstructor;
@@ -16,11 +16,11 @@ public Conversation start() {
         return null;
     }
 
-    public Conversation getByID(UUID id) throws ConversationNotFound {
+    public Conversation getByID(UUID id) throws ConversationNotFoundException {
         return null;
     }
 
-    public Conversation update(UUID id, ConversationRequest conversationRequest) throws ConversationNotFound {
+    public Conversation update(UUID id, ConversationRequest conversationRequest) throws ConversationNotFoundException {
         return Conversation.builder()
                 .id(id)
                 .text(getPrediction(id, conversationRequest.getText()))