How to fix and/or optimize this implementation of spring jpa query method?

Question

I am trying to implement a jpa query method from a key field defined as a JoinColumn for a ManyToOne relationship.

This is part of an application I'm working, built with Maven using Spring 5 and Jpa 2.1 versions.

Expected behavior of schema: "A" entity (primary key =a_id) must be owned by "B" entity (primary key= b_id), where B can own more than one entries in A. From the perspective of database, I need to store the foreign key b_id in A entity, but not the other way around.

class A  {

 @id
 Long a_id;

 @ManyToOne(optional = false)
 B b;
}

class B {

  @id
  Long b_id;

  @OneToMany(mappedBy = "b_id", cascade = CascadeType.ALL)
  @Transient
  private Set<Jobs> jobs;

}

//Are there any corrections or simplifications I can make to this model?

//Now I’m trying to extract all A entries, which have a specific b_id //using query methods

ARepository extends JpaRepository<A, Long> { 
    Optional<List<A>> findByB_id(Long B_id);
}

This is error I get with this approach:

Error: Unable to locate Attribute with the the given name [B_id] on this ManagedType [<package_path>.A]

Answer 1

mappedBy references the inverse relationship which is in your example b not b_id.

So change

@OneToMany(mappedBy = "b_id", cascade = CascadeType.ALL)

to

@OneToMany(mappedBy = "b", cascade = CascadeType.ALL)