adding JPA use case

src/main/java/guru/springframework/spring5webapp/bootstrap/DevBootstrap.java

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+package guru.springframework.spring5webapp.bootstrap;
+
+import guru.springframework.spring5webapp.model.Author;
+import guru.springframework.spring5webapp.model.Book;
+import guru.springframework.spring5webapp.model.Publisher;
+import guru.springframework.spring5webapp.repositories.AuthorRepository;
+import guru.springframework.spring5webapp.repositories.BookRepository;
+import guru.springframework.spring5webapp.repositories.PublisherRepository;
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.event.ContextRefreshedEvent;
+import org.springframework.stereotype.Component;
+
+@Component
+public class DevBootstrap implements ApplicationListener<ContextRefreshedEvent>{
+
+    private AuthorRepository authorRepository;
+    private BookRepository bookRepository;
+    private PublisherRepository publisherRepository;
+
+    public DevBootstrap(AuthorRepository authorRepository, BookRepository bookRepository, PublisherRepository publisherRepository) {
+
+        this.authorRepository = authorRepository;
+        this.bookRepository = bookRepository;
+        this.publisherRepository = publisherRepository;
+    }
+
+
+    @Override
+    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
+        initData();
+    }
+
+    private void initData(){
+        Publisher ericBookPublisher=new Publisher("Pearson Education","California,USA");
+        publisherRepository.save(ericBookPublisher);
+
+        Author eric=new Author("Eric","Evans");
+        Book ericBook=new Book("Domain Driven Design","1234",ericBookPublisher);
+        eric.getBooks().add(ericBook);
+        ericBook.getAuthors().add(eric);
+
+        authorRepository.save(eric);
+        bookRepository.save(ericBook);
+
+        Publisher rodBookPublisher=new Publisher("Macgraw Hill","Seattle,USA");
+        publisherRepository.save(rodBookPublisher);
+
+        Book rodBook=new Book("J2E Development Without EJB","1234",rodBookPublisher);
+        Author rod=new Author("Rod","Johnson");
+        rod.getBooks().add(rodBook);
+        rodBook.getAuthors().add(rod);
+
+        authorRepository.save(rod);
+        bookRepository.save(rodBook);
+    }
+}

src/main/java/guru/springframework/spring5webapp/controllers/AuthorController.java

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+package guru.springframework.spring5webapp.controllers;
+
+import guru.springframework.spring5webapp.repositories.AuthorRepository;
+import guru.springframework.spring5webapp.repositories.BookRepository;
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.Model;
+import org.springframework.web.bind.annotation.RequestMapping;
+
+@Controller
+public class AuthorController {
+
+    private AuthorRepository authorRepository;
+
+    public AuthorController(AuthorRepository authorRepository) {
+        this.authorRepository = authorRepository;
+    }
+
+    @RequestMapping("/authors")
+    public String getBooks(Model model){
+        model.addAttribute("authors",authorRepository.findAll());
+        return "authors";
+    }
+}
+

src/main/java/guru/springframework/spring5webapp/controllers/BookController.java

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+package guru.springframework.spring5webapp.controllers;
+
+import guru.springframework.spring5webapp.repositories.BookRepository;
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.Model;
+import org.springframework.web.bind.annotation.RequestMapping;
+
+@Controller
+public class BookController {
+
+    private BookRepository bookRepository;
+
+    public BookController(BookRepository bookRepository) {
+        this.bookRepository = bookRepository;
+    }
+
+    @RequestMapping("/books")
+    public String getBooks(Model model){
+        model.addAttribute("books",bookRepository.findAll());
+        return "books";
+    }
+}

src/main/java/guru/springframework/spring5webapp/model/Author.java

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+package guru.springframework.spring5webapp.model;
+
+import javax.persistence.*;
+import java.util.HashSet;
+import java.util.Set;
+
+@Entity
+public class Author {
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    private Long id;
+    private String firstName;
+    private String lastName;
+
+    @ManyToMany(mappedBy="authors")
+    private Set<Book> books = new HashSet<>();
+
+    public Author(String firstName, String lastName) {
+        this.firstName = firstName;
+        this.lastName = lastName;
+    }
+
+    public Author() {
+    }
+
+    public Set<Book> getBooks() {
+        return books;
+    }
+
+    public void setBooks(Set<Book> books) {
+        this.books = books;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Author author = (Author) o;
+
+        return id != null ? id.equals(author.id) : author.id == null;
+    }
+
+    @Override
+    public int hashCode() {
+        return id != null ? id.hashCode() : 0;
+    }
+
+    @Override
+    public String toString() {
+
+        return "Author{" +
+                "firstName='" + firstName + '\'' +
+                ", lastName='" + lastName + '\'' +
+                ", books=" + books +
+                '}';
+    }
+}

src/main/java/guru/springframework/spring5webapp/model/Book.java

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+package guru.springframework.spring5webapp.model;
+
+import javax.persistence.*;
+import java.util.HashSet;
+import java.util.Set;
+
+@Entity
+public class Book {
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    private Long id;
+    private String title;
+    private String isbn;
+
+   // @OneToOne(fetch = FetchType.LAZY,mappedBy="book")
+   @OneToOne
+    private Publisher publisher;
+
+    public Book(String title, String isbn, Publisher publisher, Set<Author> authors) {
+        this.title = title;
+        this.isbn = isbn;
+        this.publisher = publisher;
+        this.authors = authors;
+    }
+
+    public Book(String title, String isbn, Publisher publisher) {
+
+        this.title = title;
+        this.isbn = isbn;
+        this.publisher = publisher;
+    }
+
+    public Book() {
+    }
+
+    @ManyToMany
+    @JoinTable(name= "author_book", joinColumns = @JoinColumn(name = "book_id"),
+            inverseJoinColumns = @JoinColumn(name = "author_id"))
+    private Set<Author> authors=new HashSet<>();
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public Set<Author> getAuthors() {
+        return authors;
+    }
+
+    public void setAuthors(Set<Author> authors) {
+        this.authors = authors;
+    }
+
+    public String getIsbn() {
+        return isbn;
+    }
+
+    public void setIsbn(String isbn) {
+        this.isbn = isbn;
+    }
+
+    public Publisher getPublisher() {
+        return publisher;
+    }
+
+    public void setPublisher(Publisher publisher) {
+        this.publisher = publisher;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Book book = (Book) o;
+
+        return id != null ? id.equals(book.id) : book.id == null;
+    }
+
+    @Override
+    public int hashCode() {
+        return id != null ? id.hashCode() : 0;
+    }
+
+    @Override
+    public String toString() {
+        return "Book{" +
+                "title='" + title + '\'' +
+                ", isbn='" + isbn + '\'' +
+                ", publisher='" + publisher + '\'' +
+                ", authors=" + authors +
+                '}';
+    }
+}

src/main/java/guru/springframework/spring5webapp/model/Publisher.java

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+package guru.springframework.spring5webapp.model;
+
+        import javax.persistence.*;
+
+@Entity
+public class Publisher {
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    private Long id;
+    private String name;
+    private String address;
+
+    public Publisher(String name, String address) {
+        this.name = name;
+        this.address = address;
+    }
+
+    public Publisher() {
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getAddress() {
+        return address;
+    }
+
+    public void setAddress(String address) {
+        this.address = address;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        Publisher publisher = (Publisher) o;
+
+        return id != null ? id.equals(publisher.id) : publisher.id == null;
+    }
+
+    @Override
+    public int hashCode() {
+        return id != null ? id.hashCode() : 0;
+    }
+
+    @Override
+    public String toString() {
+        return "Publisher{" +
+                "name='" + name + '\'' +
+                ", address='" + address + '\'' +
+                '}';
+    }
+}
+

src/main/java/guru/springframework/spring5webapp/repositories/AuthorRepository.java

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+package guru.springframework.spring5webapp.repositories;
+
+import guru.springframework.spring5webapp.model.Author;
+import org.springframework.data.repository.CrudRepository;
+
+public interface AuthorRepository extends CrudRepository<Author, Long>{
+}

src/main/java/guru/springframework/spring5webapp/repositories/BookRepository.java

@@ -0,0 +1,7 @@
+package guru.springframework.spring5webapp.repositories;
+
+import guru.springframework.spring5webapp.model.Book;
+import org.springframework.data.repository.CrudRepository;
+
+public interface BookRepository extends CrudRepository<Book, Long> {
+}

src/main/java/guru/springframework/spring5webapp/repositories/PublisherRepository.java

@@ -0,0 +1,7 @@
+package guru.springframework.spring5webapp.repositories;
+
+import guru.springframework.spring5webapp.model.Publisher;
+import org.springframework.data.repository.CrudRepository;
+
+public interface PublisherRepository extends CrudRepository<Publisher,Long>{
+}

src/main/resources/application.properties

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+spring.h2.console.enabled = true