[EDIT] userIdによる収支検索、期間設定機能がある検索、収入・支出の検索機能のサービス段を作成しました。

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

@@ -1,5 +1,19 @@
 package com.example.demo.app.domain.service;
 
+import java.time.LocalDate;
+import java.util.List;
+import java.util.Map;
+
+import com.example.demo.app.domain.model.TransactionModel;
+
 public interface TransactionService {
 
+	public Map<LocalDate, List<TransactionModel>> findAllByDate(LocalDate startDate, LocalDate endDate, Long userId);
+	
+	public TransactionModel findByUserId(TransactionModel transactionModel);
+	
+	public int findTotalIncome(LocalDate startDate, LocalDate endDate, Long userId);
+	
+	public int findTotalexpense(LocalDate startDate, LocalDate endDate, Long userId);
+	
 }

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

@@ -1,10 +1,60 @@
 package com.example.demo.app.domain.service.impl;
 
+import java.time.LocalDate;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
 import org.springframework.stereotype.Service;
 
+import com.example.demo.app.domain.model.TransactionModel;
 import com.example.demo.app.domain.service.TransactionService;
+import com.example.demo.app.infra.entity.TransactionEntity;
+import com.example.demo.app.infra.repository.TransactionRepository;
+
+import lombok.RequiredArgsConstructor;
 
 @Service
-public class TransactionServiceImpl implements TransactionService{
+@RequiredArgsConstructor
+public class TransactionServiceImpl implements TransactionService {
+
+	private final TransactionRepository transactionRepository;
+
+	public Map<LocalDate, List<TransactionModel>> findAllByDate(LocalDate startDate, LocalDate endDate, Long userId) {
+
+		List<TransactionEntity> transactionEntityList = transactionRepository.findAllByDateAndUserId(startDate, endDate,
+				userId);
+
+		List<TransactionModel> transactionModelList = TransactionModel
+				.convertFrom(transactionEntityList);
+
+		Map<LocalDate, List<TransactionModel>> transactionModelMap = transactionModelList.stream()
+				.collect(Collectors.groupingBy(TransactionModel::getTransactionDate));
+
+		return transactionModelMap;
+
+	}
+	
+	public int findTotalIncome(LocalDate startDate, LocalDate endDate, Long userId) {
+		
+		return transactionRepository.findTotalIncome(startDate, endDate, userId);
+		
+	}
+	public int findTotalexpense(LocalDate startDate, LocalDate endDate, Long userId) {
+		
+		return transactionRepository.findTotalIncome(startDate, endDate, userId);
+		
+	}
+
+	public TransactionModel findByUserId(TransactionModel transactionModel) {
+
+		TransactionEntity transactionEntity = transactionRepository.findByUserId(transactionModel.getUserId());
+
+		if (transactionEntity == null) {
+			return null;
+		}
+
+		return TransactionModel.convertFrom(transactionEntity);
+	}
 
 }