@@ -1,113 +1,93 @@
 package com.ll.nbe342team8.domain.book.book.service;
 
-import com.ll.nbe342team8.domain.book.book.dto.BookPatchRequestDto;
-import com.ll.nbe342team8.domain.book.book.dto.BookResponseDto;
-import com.ll.nbe342team8.domain.book.book.dto.ExternalBookDto;
-import com.ll.nbe342team8.domain.book.book.entity.Book;
-import com.ll.nbe342team8.domain.book.book.repository.BookRepository;
-import com.ll.nbe342team8.domain.book.book.type.SortType;
-import jakarta.persistence.EntityNotFoundException;
-import lombok.RequiredArgsConstructor;
+import java.util.ArrayList;
+import java.util.List;
+
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
+import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
-import java.time.LocalDate;
-import java.util.ArrayList;
-import java.util.List;
+import com.ll.nbe342team8.domain.book.book.entity.Book;
+import com.ll.nbe342team8.domain.book.book.repository.BookRepository;
+import com.ll.nbe342team8.domain.book.book.type.BookSortType;
+import com.ll.nbe342team8.domain.book.book.type.SearchType;
+import com.ll.nbe342team8.global.exceptions.ServiceException;
+
+import lombok.RequiredArgsConstructor;
 
 @Service
 @RequiredArgsConstructor
 public class BookService {
 
-    private final ExternalBookApiService externalBookApiService;
-    private final BookRepository bookRepository;
-
-    public Page<Book> getAllBooks(int page, int pageSize, SortType sortType) {
-        List<Sort.Order> sorts = new ArrayList<>();
-        sorts.add(sortType.getOrder());
-
-        Pageable pageable = PageRequest.of(page, pageSize, Sort.by(sorts));
-        return bookRepository.findAll(pageable);
-    }
-
-    public Book getBookById(Long id) {
-        if (id == null) {
-            throw new IllegalArgumentException("ID 값이 null입니다.");
-        }
-        return bookRepository.findById(id)
-                .orElseThrow(() -> new IllegalArgumentException("해당 ID(" + id + ")의 책을 찾을 수 없습니다."));
-    }
-
-    public long count() {
-        return bookRepository.count();
-    }
-
-    public Book create(Book book) {
-        return bookRepository.save(book);
-    }
-
-    public Book createReview(Book book, float rating) {
-        book.createReview(rating);
-        return bookRepository.save(book);
-    }
-
-    public Book deleteReview(Book book, float rating) {
-        book.deleteReview(rating);
-        return bookRepository.save(book);
-    }
-
-    public Page<Book> searchBooks(int page, int pageSize, SortType sortType, String title) {
-        List<Sort.Order> sorts = new ArrayList<>();
-        sorts.add(sortType.getOrder());
-
-        Pageable pageable = PageRequest.of(page, pageSize, Sort.by(sorts));
-        return bookRepository.findBooksByTitleContaining(title, pageable);
-    }
-
-    // 도서 추가
-    @Transactional
-    public Book addBook(String isbn13) {
-
-        if (bookRepository.existsByIsbn13(isbn13)) {
-            throw new IllegalArgumentException("이미 등록된 도서입니다.");
-        }
-
-        ExternalBookDto externalBookDto = externalBookApiService.searchBook(isbn13);
-
-        Book book = mapToEntity(externalBookDto);
-
-        return bookRepository.save(book);
-    }
-
-    private Book mapToEntity(ExternalBookDto dto) {
-        return Book.builder()
-                .title(dto.getTitle())
-                .author(dto.getAuthor())
-                .isbn(dto.getIsbn())
-                .isbn13(dto.getIsbn13())
-                .pubDate(LocalDate.parse(dto.getPubDate()))
-                .priceStandard(dto.getPriceStandard())
-                .pricesSales(dto.getPriceSales())
-                .toc(dto.getToc())
-                .coverImage(dto.getCover())
-                .description(dto.getDescription())
-                .descriptionImage(dto.getDescriptionImage())
-                .categoryId(dto.getCategoryId())
-                .build();
-    }
-
-    // 도서 정보 수정
-    @Transactional
-    public BookResponseDto updateBookPart(Long bookId, BookPatchRequestDto requestDto) {
-        Book book = bookRepository.findById(bookId)
-                .orElseThrow(() -> new EntityNotFoundException("책을 찾을 수 없습니다."));
-
-        book.update(requestDto); // DTO 에서 null 이 아닌 값만 업데이트
-
-        return BookResponseDto.from(book);
-    }
-}
\ No newline at end of file
+	private final ExternalBookApiService externalBookApiService;
+	private final BookRepository bookRepository;
+
+	public Page<Book> getAllBooks(int page, int pageSize, BookSortType bookSortType) {
+		List<Sort.Order> sorts = new ArrayList<>();
+		sorts.add(bookSortType.getOrder());
+
+		if (!(bookSortType == BookSortType.PUBLISHED_DATE)) { // 출간일을 보조 정렬 기준으로 추가
+			BookSortType baseSort = BookSortType.PUBLISHED_DATE;
+			sorts.add(baseSort.getOrder());
+		}
+
+		Pageable pageable = PageRequest.of(page, pageSize, Sort.by(sorts));
+		return bookRepository.findAll(pageable);
+	}
+
+	public Book getBookById(Long id) {
+		// Todo: GlobalExceptionHandler 를 통해 처리하도록 수정
+
+		return bookRepository.findById(id)
+				.orElseThrow(() -> new ServiceException(HttpStatus.NOT_FOUND.value(), "id에 해당하는 책이 없습니다."));
+	}
+
+	public long count() {
+		return bookRepository.count();
+	}
+
+	public Book create(Book book) {
+		return bookRepository.save(book);
+	}
+
+	public Book createReview(Book book, Double rating) {
+		book.createReview(rating);
+		return bookRepository.save(book);
+	}
+
+	public Book deleteReview(Book book, Double rating) {
+		book.deleteReview(rating);
+		return bookRepository.save(book);
+	}
+
+	@Transactional(readOnly = true)
+	public Page<Book> searchBooks(int page, int pageSize, BookSortType bookSortType, SearchType searchType, String keyword) {
+		Pageable pageable;
+		// 판매량, 평점, 리뷰 정렬 시 보조 정렬 기준으로 출간일(pubDate) 적용
+		if (bookSortType == BookSortType.SALES_POINT || bookSortType == BookSortType.RATING || bookSortType == BookSortType.REVIEW_COUNT) {
+			pageable = PageRequest.of(page, pageSize, Sort.by(
+					new Sort.Order(bookSortType.getOrder().getDirection(), bookSortType.getOrder().getProperty()),
+					new Sort.Order(Sort.Direction.DESC, "pubDate")
+			));
+		} else {
+			pageable = PageRequest.of(page, pageSize, Sort.by(bookSortType.getOrder()));
+		}
+
+		switch (searchType) {
+			case AUTHOR:
+				return bookRepository.findBooksByAuthorContaining(keyword, pageable);
+			case ISBN13:
+				return bookRepository.findBooksByIsbn13(keyword, pageable);
+			case PUBLISHER:
+				return bookRepository.findBooksByPublisherContaining(keyword, pageable);
+			case TITLE:
+			default:
+				return bookRepository.findBooksByTitleContaining(keyword, pageable);
+		}
+	}
+}
+

리뷰: JDK 17로 넘어가면서 switch 구문이 어떻게 변했는지 알아보시면 좋을 것 같습니다.