#17 - Add derived query for ISBN

src/main/java/com/karankumar/booksapi/repository/BookRepository.java

@@ -24,5 +24,6 @@ public interface BookRepository extends CrudRepository<Book, Long> {
 
     @Query("SELECT DISTINCT b FROM Book b LEFT JOIN FETCH b.authors")
     List<Book> findAllBooks();
-
+
+    Book findBookByIsbn13(String isbn13);
 }

src/main/java/com/karankumar/booksapi/resolver/QueryResolver.java

@@ -39,4 +39,8 @@ public Iterable<Book> findAllBooks() {
     public Iterable<Author> findAllAuthors() {
         return authorRepository.findAllAuthors();
     }
+
+    public Book findBookByIsbn13(String isbn13) {
+        return bookRepository.findBookByIsbn13(isbn13);
+    }
 }

src/main/resources/graphql/query.graphqls

@@ -1,3 +1,4 @@
 type Query {
     findAllBooks: [Book]!
-}
+    findBookByIsbn13(isbn13: String!): Book!
+}

src/test/java/com/karankumar/booksapi/repository/BookRepositoryTest.java

@@ -17,12 +17,7 @@
 
 import com.karankumar.booksapi.model.Author;
 import com.karankumar.booksapi.model.Book;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.HashSet;
-import java.util.List;
-import org.junit.jupiter.api.AfterEach;
+import com.karankumar.booksapi.model.Language;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
@@ -31,6 +26,9 @@
 import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
 
+import java.util.Arrays;
+import java.util.List;
+
 import static com.karankumar.booksapi.repository.RepositoryTestUtils.createBook;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.SoftAssertions.assertSoftly;
@@ -39,7 +37,8 @@
 @ExtendWith(SpringExtension.class)
 @DisplayName("BookRepository should")
 class BookRepositoryTest {
-
+    private static final String ISBN = "978-3-16-148410-0";
+
     private final BookRepository bookRepository;
     private final AuthorRepository authorRepository;
 
@@ -74,15 +73,35 @@ void findSavedBooks() {
             softly.assertThat(result).containsExactlyInAnyOrder(book);
         });
     }
+
+    @Test
+    @DisplayName("find book with isbn")
+    void findBookByIsbn() {
+        // given
+        createAndSaveAuthors();
+        Book book = createBookwithISBN();
+        bookRepository.save(book);
+
+        // when
+        Book result = bookRepository.findBookByIsbn13(ISBN);
+
+        // then
+        assertThat(result).isEqualTo(book);
+    }
 
     private void createAndSaveAuthors() {
         author1 = new Author("Kevlin", "Henney");
         author2 = new Author("Trisha", "Gee");
         saveAllAuthors(author1, author2);
     }
 
+    private Book createBookwithISBN() {
+        Book book = new Book("Game of APIs", new Author[]{author1, author2} , Language.ENGLISH);
+        book.setIsbn13(ISBN);
+        return book;
+    }
+
     private void saveAllAuthors(Author... authors) {
         Arrays.stream(authors).forEach(authorRepository::save);
     }
-
 }