One To Many Relationship Supporting Reads but not INSERTS

问题

I am using spring boot (verson 2.1.1) to create an application that needs to one-to-many & many-to-one relationship between two model classes with below requirements

The model classes are

@Entity
@Table(name="ORGANIZATIONS")
public class Organization{

    @Id
    @GeneratedValue
    Private long id;

    @Column(unique=true)
    Private String name;
}

@Entity
@Table(name="DEPARTMENTS")
Public class Department{

   @Id
   @GeneratedValue
   Private long id;

   @Column(unique=true)
   Private String name;


//…

}

Requirements

1. Both organizations and departments should be created by separate respective rest api's.
   • Through the POST /organizations api we should be able to create an organization without creating departments in the same api call. In fact the api should fail I tried to pass the json element for department as part of the POST /organizations call.
   • When calling POST /departments I should be able to pass the organization id to associate the newly created department with the organization.
2. The GET /organizations api call should return the Collection as part of the organization object

The questions are

1. How do I associate the two model objects ? Do I add @OneToMany in Organization? What attributes do I pass to @OneToMany? Do I need a similar @ManyToOne on the other side - department?

2. Do I need any special considerations on the REST controllers?

回答1:

You will need @ManyToOne for persisting in Department only but you most likely will need @OneToMany in Organization for the GET request.

Just make sure, when saving the Department, that you need to:

• Fetch from db the organization
• Set the fetched organization on the department object
• Add the department to the Organization.departments list
• Persist the department

For the error handling return a BAD_REQUEST response:

return new ResponseEntity<>(HttpStatus.BAD_REQUEST);

来源：https://stackoverflow.com/questions/54309296/one-to-many-relationship-supporting-reads-but-not-inserts