adding publisher interface, class, & bootstrap data

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

@@ -0,0 +1,85 @@
+package guru.springframework.spring5webapp.domain;
+
+import javax.persistence.*;
+import java.util.Objects;
+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;
+
+    public Author() {
+    }
+
+    public Author(String firstName, String lastName, Set<Book> books) {
+        this.firstName = firstName;
+        this.lastName = lastName;
+        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;
+    }
+
+    public Set<Book> getBooks() {
+        return books;
+    }
+
+    public void setBooks(Set<Book> books) {
+        this.books = books;
+    }
+
+
+    // TO STRING FOR JSON TYPE DATA
+    @Override
+    public String toString() {
+        return "Author{" +
+                "id=" + id +
+                ", firstName='" + firstName + '\'' +
+                ", lastName='" + lastName + '\'' +
+                ", books=" + books +
+                '}';
+    }
+
+    // SETTING UP THE EQUALS & HASHCODE FUNCTION
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        Author author = (Author) o;
+
+        return Objects.equals(id, author.id);
+    }
+
+    @Override
+    public int hashCode() {
+        return id != null ? id.hashCode() : 0;
+    }
+}

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

@@ -0,0 +1,91 @@
+package guru.springframework.spring5webapp.domain;
+
+import javax.persistence.*;
+import java.util.Objects;
+import java.util.Set;
+
+@Entity
+public class Book {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    private Long id;
+
+    private String title;
+    private String isbn;
+
+    /*
+    Setting up the relationships between author and books
+    */
+    @ManyToMany
+    @JoinTable(name = "author_book", joinColumns = @JoinColumn(name = "book_id"),
+    inverseJoinColumns = @JoinColumn(name = "author_id"))
+    private Set<Author> authors;
+
+    public Book() {
+    }
+
+    public Book(String title, String isbn, Set<Author> authors) {
+        this.title = title;
+        this.isbn = isbn;
+
+        this.authors = authors;
+    }
+
+    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 String getIsbn() {
+        return isbn;
+    }
+
+    public void setIsbn(String isbn) {
+        this.isbn = isbn;
+    }
+
+    public Set<Author> getAuthors() {
+        return authors;
+    }
+
+    public void setAuthors(Set<Author> authors) {
+        this.authors = authors;
+    }
+
+    @Override
+    public String toString() {
+        return "Book{" +
+                "id=" + id +
+                ", title='" + title + '\'' +
+                ", isbn='" + isbn + '\'' +
+                ", authors=" + authors +
+                '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        Book book = (Book) o;
+
+        return Objects.equals(id, book.id);
+    }
+
+    @Override
+    public int hashCode() {
+        return id != null ? id.hashCode() : 0;
+    }
+}