[Refactor] JPA 연관관계 매핑

src/main/java/com/jiyunio/todolist/category/Category.java

@@ -1,12 +1,15 @@
 package com.jiyunio.todolist.category;
 
 import com.jiyunio.todolist.member.Member;
+import com.jiyunio.todolist.todo.Todo;
 import jakarta.persistence.*;
 import lombok.AccessLevel;
 import lombok.Builder;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 
+import java.util.List;
+
 @Getter
 @NoArgsConstructor(access = AccessLevel.PROTECTED)
 @Entity
@@ -24,11 +27,16 @@ public class Category {
 
     private String color;
 
+    @OneToMany(fetch = FetchType.LAZY)
+    @JoinColumn(name = "todoId")
+    List<Todo> todo;
+
     @Builder
-    protected Category(Member member, String content, String color) {
+    protected Category(Member member, String content, String color, List<Todo> todo) {
         this.member = member;
         this.content = content;
         this.color = color;
+        this.todo = todo;
     }
 
     protected void updateCategory(CategoryDTO categoryDTO) {

src/main/java/com/jiyunio/todolist/category/CategoryService.java

@@ -5,15 +5,18 @@
 import com.jiyunio.todolist.member.Member;
 import com.jiyunio.todolist.member.MemberRepository;
 import com.jiyunio.todolist.responseDTO.ResponseCategoryDTO;
+import com.jiyunio.todolist.todo.Todo;
 import lombok.RequiredArgsConstructor;
 import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
 
 import java.util.ArrayList;
 import java.util.List;
 
 @Service
 @RequiredArgsConstructor
+@Transactional
 public class CategoryService {
     private final CategoryRepository categoryRepository;
     private final MemberRepository memberRepository;
@@ -56,6 +59,8 @@ public ResponseCategoryDTO updateCategory(Long categoryId, CategoryDTO categoryD
         category.updateCategory(categoryDTO);
         categoryRepository.save(category);
 
+        List<Todo> todoList = category.getTodo();
+
         return ResponseCategoryDTO.builder()
                 .categoryId(category.getId())
                 .content(category.getContent())

src/main/java/com/jiyunio/todolist/todo/Todo.java

@@ -35,7 +35,6 @@ public class Todo {
 
     private LocalDate setDate;
 
-    private String color;
 
     @Builder
     protected Todo(Member member, String content, Boolean checked, String category,