Spring JPARepository querying many to many intersection table - spring

Question

I have 3 entity classes as follows (Example taken from https://hellokoding.com/jpa-many-to-many-extra-columns-relationship-mapping-example-with-spring-boot-maven-and-mysql/)
Book class
#Entity
public class Book{
private int id;
private String name;
private Set<BookPublisher> bookPublishers;
public Book() {
}
public Book(String name) {
this.name = name;
bookPublishers = new HashSet<>();
}
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
#OneToMany(mappedBy = "book", cascade = CascadeType.ALL, orphanRemoval = true)
public Set<BookPublisher> getBookPublishers() {
return bookPublishers;
}
public void setBookPublishers(Set<BookPublisher> bookPublishers) {
this.bookPublishers = bookPublishers;
}
}
Publisher class
#Entity
public class Publisher {
private int id;
private String name;
private Set<BookPublisher> bookPublishers;
public Publisher(){
}
public Publisher(String name){
this.name = name;
}
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
#OneToMany(mappedBy = "publisher")
public Set<BookPublisher> getBookPublishers() {
return bookPublishers;
}
public void setBookPublishers(Set<BookPublisher> bookPublishers) {
this.bookPublishers = bookPublishers;
}
}
Intersection Table
#Entity
#Table(name = "book_publisher")
public class BookPublisher implements Serializable{
private Book book;
private Publisher publisher;
private Date publishedDate;
#Id
#ManyToOne
#JoinColumn(name = "book_id")
public Book getBook() {
return book;
}
public void setBook(Book book) {
this.book = book;
}
#Id
#ManyToOne
#JoinColumn(name = "publisher_id")
public Publisher getPublisher() {
return publisher;
}
public void setPublisher(Publisher publisher) {
this.publisher = publisher;
}
#Column(name = "published_date")
public Date getPublishedDate() {
return publishedDate;
}
public void setPublishedDate(Date publishedDate) {
this.publishedDate = publishedDate;
}
}
I want to query 2 things,
Get list of books belonging to a particular publisher e.g. get all books associated with publisher 100
Get list of books not associated with a particular publisher e.g. get all books not associated with publisher 100
I want to achieve this using a simple JPARepository query if possible like findByXYZIn(...) etc.
Please let me know if querying a many to many relation is possible using JPA repository queries and if yes, whether I can do it directly or would it require any changes in the entity classes

Answer 1

In BookRepository
Get publisher's books
findBooksByBookPublishersPublisherId(Long publisherId)
Get books not published by publisher
findBooksByBookPublishersPublisherIdNot(Long publisherId)
IMHO Publication is much more apropriate name then BookPublisher in your case as Publisher by itself could be BookPublisher (a published that publishing books)

Answer 2

I'm not sure if you can make it just by method name. But you definitely can use JPA query. Something like this: "SELECT b FROM Book b JOIN b.bookPublishers bp JOIN bp.publisher p WHERE p.id = ?1". and with not equal for the second case

Answer 3

Well you can use named Queries to fulfill your requirements:
#Query("select b from Book b where b.publisher.idd = ?1")
Book findByPublisherId(int id);
#Query("select b from Book b where b.publisher.idd <> ?1")
Book findByDifferentPublisherId(int id);
Take a look at Using #Query Spring docs for further details.