fix: throw ResourceNotFoundException instead of returning null, replace full-table-scan list queries with JPQL

src/main/java/de/zendric/app/xpensely_server/model/Exception/ResourceNotFoundException.java

@@ -0,0 +1,11 @@
+package de.zendric.app.xpensely_server.model.Exception;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.ResponseStatus;
+
+@ResponseStatus(HttpStatus.NOT_FOUND)
+public class ResourceNotFoundException extends RuntimeException {
+    public ResourceNotFoundException(String message) {
+        super(message);
+    }
+}

src/main/java/de/zendric/app/xpensely_server/repo/ExpenseListRepository.java

@@ -3,13 +3,24 @@ package de.zendric.app.xpensely_server.repo;
 import java.util.List;
 
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
 import de.zendric.app.xpensely_server.model.ExpenseList;
 
 @Repository
 public interface ExpenseListRepository extends JpaRepository<ExpenseList, Long> {
+
     List<ExpenseList> findByOwnerId(Long ownerId);
 
     ExpenseList findByInviteCode(String inviteCode);
-}
+
+    @Query("SELECT el FROM ExpenseList el WHERE el.owner.id = :userId OR el.sharedWith.id = :sharedUserId")
+    List<ExpenseList> findByOwnerIdOrSharedWithId(@Param("userId") Long userId,
+                                                   @Param("sharedUserId") Long sharedUserId);
+
+    @Query("SELECT el FROM ExpenseList el WHERE el.owner.username = :username OR el.sharedWith.username = :sharedUsername")
+    List<ExpenseList> findByOwnerUsernameOrSharedWithUsername(@Param("username") String username,
+                                                               @Param("sharedUsername") String sharedUsername);
+}

src/main/java/de/zendric/app/xpensely_server/services/ExpenseListService.java

@@ -7,7 +7,6 @@ import java.util.List;
 import java.util.Optional;
 import java.util.UUID;
 
-import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
@@ -18,20 +17,15 @@ import de.zendric.app.xpensely_server.model.XpenselyCustomCategory;
 import de.zendric.app.xpensely_server.repo.ExpenseListRepository;
 import de.zendric.app.xpensely_server.repo.ExpenseRepository;
 import de.zendric.app.xpensely_server.repo.XpenselyCustomCategoryRepository;
-import jakarta.persistence.EntityManager;
 
 @Service
 @Transactional
 public class ExpenseListService {
 
-    private ExpenseListRepository repository;
+    private final ExpenseListRepository repository;
     private final ExpenseRepository expenseRepository;
-    private XpenselyCustomCategoryRepository customCategoryRepository;
+    private final XpenselyCustomCategoryRepository customCategoryRepository;
 
-    @Autowired
-    private EntityManager entityManager;
-
-    @Autowired
     public ExpenseListService(ExpenseListRepository repository, ExpenseRepository expenseRepository,
             XpenselyCustomCategoryRepository customCategoryRepository) {
         this.repository = repository;
@@ -68,38 +62,11 @@ public class ExpenseListService {
     }
 
     public List<ExpenseList> findByUserId(Long id) {
-        List<ExpenseList> allLists = repository.findAll();
-        List<ExpenseList> userSpecificList = new ArrayList<>();
-        for (ExpenseList expenseList : allLists) {
-            AppUser sharedWith = expenseList.getSharedWith();
-
-            if (expenseList.getOwner().getId().equals(id)) {
-                userSpecificList.add(expenseList);
-            } else {
-                if (sharedWith != null && sharedWith.getId().equals(id)) {
-                    userSpecificList.add(expenseList);
-                }
-            }
-        }
-        return userSpecificList;
+        return repository.findByOwnerIdOrSharedWithId(id, id);
     }
 
     public List<ExpenseList> findByUsername(String username) {
-        List<ExpenseList> allLists = repository.findAll();
-        List<ExpenseList> userSpecificList = new ArrayList<>();
-        for (ExpenseList expenseList : allLists) {
-            AppUser sharedWith = expenseList.getSharedWith();
-
-            if (expenseList.getOwner().getUsername().equals(username)) {
-                userSpecificList.add(expenseList);
-            } else {
-                if (sharedWith != null && sharedWith.getUsername().equals(username)) {
-                    userSpecificList.add(expenseList);
-                }
-            }
-        }
-        return userSpecificList;
-
+        return repository.findByOwnerUsernameOrSharedWithUsername(username, username);
     }
 
     public Expense addExpenseToList(Long expenseListId, Expense expense) {

src/main/java/de/zendric/app/xpensely_server/services/UserService.java

@@ -1,11 +1,11 @@
 package de.zendric.app.xpensely_server.services;
 
 import java.util.List;
-import java.util.Optional;
 
 import org.springframework.stereotype.Service;
 
 import de.zendric.app.xpensely_server.model.AppUser;
+import de.zendric.app.xpensely_server.model.Exception.ResourceNotFoundException;
 import de.zendric.app.xpensely_server.model.Exception.UsernameAlreadyExistsException;
 import de.zendric.app.xpensely_server.repo.UserRepository;
 
@@ -29,36 +29,24 @@ public class UserService {
     }
 
     public AppUser getUser(Long id) {
-        Optional<AppUser> user = userRepository.findById(id);
-        if (user.isPresent()) {
-            return user.get();
-        } else
-            return null;
+        return userRepository.findById(id)
+                .orElseThrow(() -> new ResourceNotFoundException("User not found with id: " + id));
     }
 
     public AppUser deleteUserById(Long id) {
-        Optional<AppUser> user = userRepository.findById(id);
-        if (user.isPresent()) {
-            userRepository.deleteById(id);
-            return user.get();
-        } else
-            return null;
+        AppUser user = userRepository.findById(id)
+                .orElseThrow(() -> new ResourceNotFoundException("User not found with id: " + id));
+        userRepository.deleteById(id);
+        return user;
     }
 
     public AppUser getUserByName(String username) {
-        Optional<AppUser> optUser = userRepository.findByUsername(username);
-        if (optUser.isPresent()) {
-            return optUser.get();
-        } else
-            return null;
+        return userRepository.findByUsername(username)
+                .orElseThrow(() -> new ResourceNotFoundException("User not found: " + username));
     }
 
     public AppUser getUserByGoogleId(String id) {
-        Optional<AppUser> optUser = userRepository.findByGoogleId(id);
-        if (optUser.isPresent()) {
-            return optUser.get();
-        } else
-            return null;
+        return userRepository.findByGoogleId(id)
+                .orElseThrow(() -> new ResourceNotFoundException("User not found with Google ID: " + id));
     }
-
-}
+}