Fetch association in batches

Author: AnghelLeonard

HibernateSpringBootLoadBatchAssociation/src/main/java/com/bookstore/MainApplication.java

@@ -20,7 +20,11 @@ public static void main(String[] args) {
     @Bean
     public ApplicationRunner init() {
         return args -> {
-            bookstoreService.displayAuthorsAndBooks();
+          //  System.out.println("\n\nLoad authors with books:");
+          //  bookstoreService.displayAuthorsAndBooks();
+            
+            System.out.println("\n\nLoad books with authors:");
+            bookstoreService.displayBooksAndAuthors();
         };
     }
 }

HibernateSpringBootLoadBatchAssociation/src/main/java/com/bookstore/entity/Author.java

@@ -13,6 +13,7 @@
 import org.hibernate.annotations.BatchSize;
 
 @Entity
+@BatchSize(size = 3)
 public class Author implements Serializable {
 
     private static final long serialVersionUID = 1L;
@@ -27,7 +28,7 @@ public class Author implements Serializable {
 
     @OneToMany(cascade = CascadeType.ALL,
             mappedBy = "author", orphanRemoval = true)
-    @BatchSize(size = 3)
+    //@BatchSize(size = 3)
     private List<Book> books = new ArrayList<>();
 
     public void addBook(Book book) {

HibernateSpringBootLoadBatchAssociation/src/main/java/com/bookstore/repository/BookRepository.java

@@ -0,0 +1,9 @@
+package com.bookstore.repository;
+
+import com.bookstore.entity.Book;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+@Repository
+public interface BookRepository extends JpaRepository<Book, Long> {
+}

HibernateSpringBootLoadBatchAssociation/src/main/java/com/bookstore/service/BookstoreService.java

@@ -2,6 +2,8 @@
 
 import com.bookstore.repository.AuthorRepository;
 import com.bookstore.entity.Author;
+import com.bookstore.entity.Book;
+import com.bookstore.repository.BookRepository;
 import java.util.List;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -10,10 +12,13 @@
 public class BookstoreService {
 
     private final AuthorRepository authorRepository;
+    private final BookRepository bookRepository;
 
-    public BookstoreService(AuthorRepository authorRepository) {
+    public BookstoreService(AuthorRepository authorRepository,
+            BookRepository bookRepository) {
 
         this.authorRepository = authorRepository;
+        this.bookRepository = bookRepository;
     }
 
     @Transactional(readOnly = true)
@@ -27,4 +32,15 @@ public void displayAuthorsAndBooks() {
                     + author.getBooks().size() + ", " + author.getBooks());
         }
     }
+
+    @Transactional(readOnly = true)
+    public void displayBooksAndAuthors() {
+
+        List<Book> books = bookRepository.findAll();
+
+        for (Book book : books) {
+            System.out.println("Book: " + book.getTitle());
+            System.out.println("Author: " + book.getAuthor());
+        }
+    }
 }