Spring JPA | Search in Many to Many Relationship - mysql

Question

I have 2 tables Book and Author in a Many to Many Relationship using a candidate key table author_book which has primary keys of both author and Book.
I'm trying to get all books from a given author by AUTHOR_ID, maybe after if it works I'll try to do search by name
create table author_book(
`AUTHOR_ID` INT,
`BOOK_ID` INT
);
`
create table author(
`AUTHOR_ID` int auto_increment,
`FIRST_NAME` varchar(255),
`LAST_NAME` varchar(255),
`EMAIL` varchar(30),
`CONTACT_NO` VARCHAR(10),
primary key(AUTHOR_ID)
);
create table book(
`BOOK_ID` int auto_increment,
`TITLE` varchar(255),
`SUBJECT` varchar(255),
`PUBLISHED_YEAR` int,
`ISBN` varchar(30),
`QUANTITY` int,
`SHELF_DETAILS` varchar(255),
`PUBLISHER_ID` int,
`BOOK_COST` INT,
primary key(BOOK_ID)
);
I decided I'll create AUTHOR_NAME using CONCAT
I tried this query for search by author_id
#Query("select b from Books b where b.bookId in (select a.bookId from author_book a where a.author_id = :Id)")
but I'm getting error that author_book is not mapped so do I need to create another entity for this class to perform any operations b/w these 2 class? I'm also not sure if nested queries work in JPQL, this was basically a hunch.
My Books Entity
#Entity
#Table(name = "book")
public class Books implements Serializable{
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name="BOOK_ID")
private int bookId;
#Column(name="TITLE")
private String title;
#Column(name="SUBJECT")
private String subject;
#Column(name="PUBLISHED_YEAR")
private int publishedYear;
#Column(name="ISBN")
private String isbn;
#Column(name="QUANTITY")
private int quantity;
#Column(name="SHELF_DETAILS")
private String shelfDetails;
#Column(name="BOOK_COST")
private int bookCost;
#JsonIgnore
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(name = "author_book",
joinColumns = { #JoinColumn(name = "BOOK_ID") },
inverseJoinColumns = { #JoinColumn(name = "AUTHOR_ID") })
private Set<Authors> authors = new HashSet<Authors>();
#JsonIgnore
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name="PUBLISHER_ID")
private Publishers publisher;
// getters and setters
}
My Authors Entity
#Entity
#Table(name="author")
public class Authors {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="AUTHOR_ID")
private int authorId;
#Column(name="FIRST_NAME")
private String firstName;
#Column(name="LAST_NAME")
private String lastName;
#Column(name="EMAIL")
private String email;
#Column(name="CONTACT_NO")
private String contactNo;
#JsonIgnore
#ManyToMany(fetch = FetchType.LAZY, mappedBy = "authors")
private Set<Books> books = new HashSet<Books>();
// Getters and setters
}

Answer 1

You should add mappedBy things in Authors Entity.
#ManyToMany(mappedBy="authors", fetch=FetchType.LAZY)
private Set<Books> books = new HashSet<Books>();