[FIX] 目標金額が現在所持金より低かった場合、エラーを表示するように修正しました。

src/main/java/com/example/demo/app/domain/service/GoalService.java

@@ -18,6 +18,8 @@ public interface GoalService {
 	
 	public void updateGoalComplete(Long userId);
 
+	public int getCurrentAmount(Long userId);
+	
 //	void deleteGoal(Long goalId);
 
 }

src/main/java/com/example/demo/app/domain/service/impl/GoalServiceImpl.java

@@ -59,13 +59,28 @@ public class GoalServiceImpl implements GoalService {
 								: (int) ((currentAmount * 100.0) / goalEntity.getTargetAmount()),
 						currentAmount)));
 
-
 		return goalModelList;
 	}
 
 	@Override
 	public GoalModel createGoal(GoalModel goalModel, Long userId) {
 
+		UserEntity userEntity = userRepository.findById(userId).orElseThrow();
+
+		int transactionTotal = userEntity.getTransactionEntityList().stream()
+				.mapToInt(t -> {
+					int sign = t.getCategoryEntity().getTransactionType() == 1 ? 1 : -1;
+					return sign * t.getAmount();
+				})
+				.sum();
+
+		// 現在の資産 = 貯蓄金 + 収支合計
+		int currentAmount = userEntity.getSaving() + transactionTotal;
+		
+		if (currentAmount >= goalModel.getTargetAmount()) {
+			return null;
+		}
+
 		GoalEntity goalEntity = GoalModel.convertTo(goalModel, userRepository.findById(userId).get());
 
 		GoalEntity savedGoalEntity = goalRepository.save(goalEntity);
@@ -108,4 +123,21 @@ public class GoalServiceImpl implements GoalService {
 		});
 	}
 
+	public int getCurrentAmount(Long userId) {
+	
+		UserEntity userEntity = userRepository.findById(userId).orElseThrow();
+
+		int transactionTotal = userEntity.getTransactionEntityList().stream()
+				.mapToInt(t -> {
+					int sign = t.getCategoryEntity().getTransactionType() == 1 ? 1 : -1;
+					return sign * t.getAmount();
+				})
+				.sum();
+
+		int currentAmount = userEntity.getSaving() + transactionTotal;
+		
+		return currentAmount;
+		
+	}
+	
 }

src/main/java/com/example/demo/app/presentation/controller/GoalController.java

@@ -267,20 +267,31 @@ public class GoalController {
 
 	@SessionCheck
 	@GetMapping(TransitionTargetPageNameKeyword.CREATE)
-	public String createGoalGet(@ModelAttribute GoalForm goalForm, HttpSession session) {
+	public String createGoalGet(@ModelAttribute GoalForm goalForm, HttpSession session, Model model) {
+
+		LoginModel loginUser = (LoginModel) session.getAttribute(SessionKeyword.LOGIN_USER);
+
+		Long userId = loginUser.getUserId();
+		
+		int currentAmount = goalService.getCurrentAmount(userId);
+		
+		model.addAttribute("currentAmount", currentAmount);
 		
 		return TransitionTargetPageNameKeyword.GOAL_CREATE_HTML;
 	}
 
 	@SessionCheck
 	@PostMapping(TransitionTargetPageNameKeyword.CREATE)
-	public String createGoalPost(@ModelAttribute GoalForm goalForm, HttpSession session) {
+	public String createGoalPost(@ModelAttribute GoalForm goalForm, HttpSession session, Model model) {
 
 		LoginModel loginUser = (LoginModel) session.getAttribute(SessionKeyword.LOGIN_USER);
 
 		Long userId = loginUser.getUserId();
 
-		goalService.createGoal(GoalModel.convertFrom(goalForm), userId);
+		if (goalService.createGoal(GoalModel.convertFrom(goalForm), userId) == null) {
+			model.addAttribute(PageReturnAttributeKeyword.MESSAGE, "現在所持金より高い金額を設定してください。");
+			return TransitionTargetPageNameKeyword.GOAL_CREATE_HTML;
+		}
 
 		return TransitionTargetPageNameKeyword.REDIRECT + TransitionTargetPageNameKeyword.GOAL;
 	}

src/main/resources/templates/goal_create.html

@@ -37,6 +37,10 @@
 					<div>
 						<label>目標金額</label>
 						<input type="number" th:field="*{targetAmount}" required min="1">
+						<span th:text="|所持金：${currentAmount}円|"></span>
+						<span th:if="${message != null}">
+							<span th:text="${message}" style="color: red;"></span>
+						</span>
 					</div>
 
 					<div>