[EDIT] 名前で検索できる機能を追加しました。

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

@@ -9,4 +9,6 @@ public interface CategoryService {
 	public List<CategoryModel> findAll();
 	
 	public CategoryModel findOne(Long categoryId);
+	
+	public CategoryModel findOneByCategoryName(String categoryName);
 }

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

@@ -14,26 +14,38 @@ import lombok.RequiredArgsConstructor;
 
 @Service
 @RequiredArgsConstructor
-public class CategoryServiceImpl implements CategoryService{
+public class CategoryServiceImpl implements CategoryService {
 
 	private final CategoryRepository categoryRepository;
-	
+
 	public List<CategoryModel> findAll() {
-		
+
 		return CategoryModel.convertFrom(categoryRepository.findAll());
-		
+
 	}
-	
+
 	public CategoryModel findOne(Long categoryId) {
-		
+
 		Optional<CategoryEntity> optionalCategoryModel = categoryRepository.findById(categoryId);
-		
+
 		if (optionalCategoryModel.isEmpty()) {
 			return null;
 		}
-		
+
 		return CategoryModel.convertFrom(optionalCategoryModel.get());
-		
+
 	}
-	
+
+	public CategoryModel findOneByCategoryName(String categoryName) {
+
+		CategoryEntity categoryModel = categoryRepository.findByCategoryName(categoryName);
+
+		if (categoryModel == null) {
+			return null;
+		}
+
+		return CategoryModel.convertFrom(categoryModel);
+
+	}
+
 }