Enhancement: Use DTOs for entity exposure in controller layer

src/main/java/com/libraryman_api/book/Book.java

@@ -78,6 +78,7 @@ public int getCopiesAvailable() {
         return copiesAvailable;
     }
 
+    public void setBookId(int bookId) {this.bookId = bookId;}
 
     public void setTitle(String title) {
         this.title = title;

src/main/java/com/libraryman_api/book/BookController.java

@@ -29,11 +29,11 @@ public class BookController {
      * @param pageable contains pagination information (page number, size, and sorting).
      * @param sortBy (optional) the field by which to sort the results.
      * @param sortDir (optional) the direction of sorting (asc or desc). Defaults to ascending.
-     * @return a {@link Page} of {@link Book} objects representing the books in the library.
+     * @return a {@link Page} of {@link BookDto} objects representing the books in the library.
      *         The results are sorted by title by default and limited to 5 books per page.
      */
     @GetMapping
-    public Page<Book> getAllBooks(@PageableDefault(page=0, size=5, sort="title") Pageable pageable,
+    public Page<BookDto> getAllBooks(@PageableDefault(page=0, size=5, sort="title") Pageable pageable,
     								@RequestParam(required = false) String sortBy,
     								@RequestParam(required = false) String sortDir) {
 
@@ -58,7 +58,7 @@ public Page<Book> getAllBooks(@PageableDefault(page=0, size=5, sort="title") Pag
      * @throws ResourceNotFoundException if the book with the specified ID is not found.
      */
     @GetMapping("/{id}")
-    public ResponseEntity<Book> getBookById(@PathVariable int id) {
+    public ResponseEntity<BookDto> getBookById(@PathVariable int id) {
         return bookService.getBookById(id)
                 .map(ResponseEntity::ok)
                 .orElseThrow(() -> new ResourceNotFoundException("Book not found"));
@@ -67,24 +67,24 @@ public ResponseEntity<Book> getBookById(@PathVariable int id) {
     /**
      * Adds a new book to the library.
      *
-     * @param book the {@link Book} object representing the new book to add.
+     * @param bookDto the {@link Book} object representing the new book to add.
      * @return the added {@link Book} object.
      */
     @PostMapping
-    public Book addBook(@RequestBody Book book) {
-        return bookService.addBook(book);
+    public BookDto addBook(@RequestBody BookDto bookDto) {
+        return bookService.addBook(bookDto);
     }
 
     /**
      * Updates an existing book in the library.
      *
      * @param id          the ID of the book to update.
-     * @param bookDetails the {@link Book} object containing the updated book details.
+     * @param bookDtoDetails the {@link Book} object containing the updated book details.
      * @return the updated {@link Book} object.
      */
     @PutMapping("/{id}")
-    public Book updateBook(@PathVariable int id, @RequestBody Book bookDetails) {
-        return bookService.updateBook(id, bookDetails);
+    public BookDto updateBook(@PathVariable int id, @RequestBody BookDto bookDtoDetails) {
+        return bookService.updateBook(id, bookDtoDetails);
     }
 
     /**

src/main/java/com/libraryman_api/book/BookService.java

@@ -46,9 +46,10 @@ public BookService(BookRepository bookRepository) {
      * @return a {@link Page} of {@link Book} representing all books
      * @throws InvalidSortFieldException if an invalid sortBy field is specified
      */
-    public Page<Book> getAllBooks(Pageable pageable) {
+    public Page<BookDto> getAllBooks(Pageable pageable) {
     	try {
-            return bookRepository.findAll(pageable);
+            Page<Book> pagedBooks = bookRepository.findAll(pageable);
+            return pagedBooks.map(this::EntityToDto);
         } catch (PropertyReferenceException ex) {
             throw new InvalidSortFieldException("The specified 'sortBy' value is invalid.");
         }
@@ -60,39 +61,44 @@ public Page<Book> getAllBooks(Pageable pageable) {
      * @param bookId the ID of the book to retrieve
      * @return an {@code Optional} containing the found book, or {@code Optional.empty()} if no book was found
      */
-    public Optional<Book> getBookById(int bookId) {
-        return bookRepository.findById(bookId);
+    public Optional<BookDto> getBookById(int bookId) {
+
+        Optional<Book> bookById = bookRepository.findById(bookId);
+        return bookById.map(this::EntityToDto);
     }
 
     /**
      * Adds a new book to the database.
      *
-     * @param book the book to be added
+     * @param bookDto the book to be added
      * @return the saved book
      */
-    public Book addBook(Book book) {
-        return bookRepository.save(book);
+    public BookDto addBook(BookDto bookDto) {
+        Book book = DtoToEntity(bookDto);
+        Book savedBook = bookRepository.save(book);
+        return EntityToDto(savedBook);
     }
 
     /**
      * Updates an existing book with the given details.
      *
      * @param bookId the ID of the book to update
-     * @param bookDetails the new details for the book
+     * @param bookDtoDetails the new details for the book
      * @return the updated book
      * @throws ResourceNotFoundException if the book with the specified ID is not found
      */
-    public Book updateBook(int bookId, Book bookDetails) {
+    public BookDto updateBook(int bookId, BookDto bookDtoDetails) {
         Book book = bookRepository.findById(bookId)
                 .orElseThrow(() -> new ResourceNotFoundException("Book not found"));
-        book.setTitle(bookDetails.getTitle());
-        book.setAuthor(bookDetails.getAuthor());
-        book.setIsbn(bookDetails.getIsbn());
-        book.setPublisher(bookDetails.getPublisher());
-        book.setPublishedYear(bookDetails.getPublishedYear());
-        book.setGenre(bookDetails.getGenre());
-        book.setCopiesAvailable(bookDetails.getCopiesAvailable());
-        return bookRepository.save(book);
+        book.setTitle(bookDtoDetails.getTitle());
+        book.setAuthor(bookDtoDetails.getAuthor());
+        book.setIsbn(bookDtoDetails.getIsbn());
+        book.setPublisher(bookDtoDetails.getPublisher());
+        book.setPublishedYear(bookDtoDetails.getPublishedYear());
+        book.setGenre(bookDtoDetails.getGenre());
+        book.setCopiesAvailable(bookDtoDetails.getCopiesAvailable());
+        Book updatedBook = bookRepository.save(book);
+        return EntityToDto(updatedBook);
     }
 
     /**
@@ -107,4 +113,29 @@ public void deleteBook(int bookId) {
         bookRepository.delete(book);
     }
 
+    public BookDto EntityToDto(Book book){
+        BookDto bookDto= new BookDto();
+        bookDto.setBookId(book.getBookId());
+        bookDto.setPublisher(book.getPublisher());
+        bookDto.setPublishedYear(book.getPublishedYear());
+        bookDto.setTitle(book.getTitle());
+        bookDto.setAuthor(book.getAuthor());
+        bookDto.setGenre(book.getGenre());
+        bookDto.setIsbn(book.getIsbn());
+        bookDto.setCopiesAvailable(book.getCopiesAvailable());
+        return bookDto;
+    }
+
+    public Book DtoToEntity(BookDto bookDto){
+         Book book= new Book();
+         book.setBookId(bookDto.getBookId());
+         book.setAuthor(bookDto.getAuthor());
+         book.setGenre(bookDto.getGenre());
+         book.setPublisher(bookDto.getPublisher());
+         book.setPublishedYear(bookDto.getPublishedYear());
+         book.setTitle(bookDto.getTitle());
+         book.setCopiesAvailable(bookDto.getCopiesAvailable());
+         book.setIsbn(bookDto.getIsbn());
+         return book;
+    }
 }

src/main/java/com/libraryman_api/borrowing/BorrowingController.java

@@ -39,7 +39,7 @@ public BorrowingController(BorrowingService borrowingService) {
      *         The results are sorted by borrow date by default and limited to 5 members per page.
      */
     @GetMapping
-    public Page<Borrowings> getAllBorrowings(@PageableDefault(page=0, size=5, sort="borrowDate") Pageable pageable,
+    public Page<BorrowingsDto> getAllBorrowings(@PageableDefault(page=0, size=5, sort="borrowDate") Pageable pageable,
 												@RequestParam(required = false) String sortBy,
 												@RequestParam(required = false) String sortDir) {
 
@@ -60,12 +60,12 @@ public Page<Borrowings> getAllBorrowings(@PageableDefault(page=0, size=5, sort="
     /**
      * Records a new book borrowing.
      *
-     * @param borrowing the {@link Borrowings} object containing borrowing details.
+     * @param borrowingsDto the {@link Borrowings} object containing borrowing details.
      * @return the saved {@link Borrowings} object representing the borrowing record.
      */
     @PostMapping
-    public Borrowings borrowBook(@RequestBody Borrowings borrowing) {
-        return borrowingService.borrowBook(borrowing);
+    public BorrowingsDto borrowBook(@RequestBody BorrowingsDto borrowingsDto) {
+        return borrowingService.borrowBook(borrowingsDto);
     }
 
     /**
@@ -74,8 +74,8 @@ public Borrowings borrowBook(@RequestBody Borrowings borrowing) {
      * @param id the ID of the borrowing record to update.
      */
     @PutMapping("/{id}/return")
-    public void returnBook(@PathVariable int id) {
-        borrowingService.returnBook(id);
+    public BorrowingsDto returnBook(@PathVariable int id) {
+        return borrowingService.returnBook(id);
     }
 
     /**
@@ -101,7 +101,7 @@ public String payFine(@PathVariable int id) {
      *         The results are sorted by borrow date by default and limited to 5 members per page.
      */
     @GetMapping("member/{memberId}")
-    public Page<Borrowings> getAllBorrowingsOfAMember(@PathVariable int memberId, 
+    public Page<BorrowingsDto> getAllBorrowingsOfAMember(@PathVariable int memberId,
     													@PageableDefault(page=0, size=5, sort="borrowDate") Pageable pageable,
     													@RequestParam(required = false) String sortBy,
     													@RequestParam(required = false) String sortDir) {
@@ -128,7 +128,7 @@ public Page<Borrowings> getAllBorrowingsOfAMember(@PathVariable int memberId,
      * @throws ResourceNotFoundException if the borrowing record with the specified ID is not found.
      */
     @GetMapping("{borrowingId}")
-    public Borrowings getBorrowingById(@PathVariable int borrowingId) {
+    public BorrowingsDto getBorrowingById(@PathVariable int borrowingId) {
         return borrowingService.getBorrowingById(borrowingId)
                 .orElseThrow(() -> new ResourceNotFoundException("Borrowing not found"));
     }