Question about entities in spring boot java

Question

package net.employee_managment.springboot.model;



import javax.persistence.*;
import javax.validation.constraints.NotNull;
import java.util.Arrays;

@Entity
@Table(name = "employee")
@Inheritance(strategy = InheritanceType.JOINED)
public class Employee {


    @Id
    @Column(name="employee_id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int employee_id;


    @NotNull
    @ManyToOne
    @JoinColumn(name="general_details_id", nullable = false)
    private GeneralDetails generalDetails;


    @NotNull
    @ManyToOne
    @JoinColumn(name="spouse_id", nullable = false)
    private Spouse spouse;

    @NotNull
    @ManyToOne
    @JoinColumn(name="address_Id")
    private Address[] addresses;

    @NotNull
    @ManyToOne
    @JoinColumn(name="child_ID")
    private Child[] children;

.... Constractors, Gettes, Setters}

Until now I could use the ID of the objects within the Employee object to link the objects and everything worked fine. But now I have an array of objects and I have a hard time figuring out how to link the Address array to the Employee object

Answer 1

The @ManyToOne constraint implies a singular relationship on the side that owns the mapping. If you want to associate multiple objects on the owner side then you really need the inverse annotation (ie @OneToMany ) and I personally always tend to associate that annotation with either a List or Set implementation (any will do). Thus your member variable declaration would look as follows:

@NotNull
@OneToMany
private Set<Address> addresses;

This way you're able to pass your Employee instance a List (or Set in this case) of Address instances and providing you have update/insert cascade enabled (as well GeneratedId's), each Address in the collection will be automatically assigned id when the parent Employee instance is persisted.