如何使用 Hibernate 更新实体而不是将其插入数据库？

Question

For example, I have a Job entity and a worker entity. when I add new job I want to assign workers to it but instead of adding it's users to the database again ( and create duplicates ) I want to just update workers ( add jobs to them when I create a new job with worker list )

example:

@Entity
@Table(name = "job")
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class Job{

  @Id
  @Column(name = "id")
  private Long id;


  @OneToMany(mappedBy = "job", fetch = FetchType.EAGER)
  private Set<Worker> workers;
}

---

@Entity
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@Table(name = "workers")
public class User extends DataAudit {

  @Id
  private Long id;


  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "job_id", referencedColumnName = "id")
  private Job job;

}

---

Worker worker1 = workerService.getWorkerById(1);
Job job = new Job(1,worker1)
jobRepo.save(job)

Answer 1

The entities should be using bidirectional OneToMany association with @JoinTable:

@Entity
@Table(name = "job")
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class Job{

  @Id
  @Column(name = "id")
  private Long id;


  @OneToMany(fetch=FetchType.LAZY)
  @JoinTable(name="job_workers", 
    joinColumns={@JoinColumn(name="job_id")},
    inverseJoinColumns={@JoinColumn(name="worker_id")}
  )
  @Cascade(org.hibernate.annotations.CascadeType.ALL)
  private Set<Worker> workers;
}

////////////////////////////////////////////////////////

@Entity
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@Table(name = "workers")
public class User extends DataAudit {

  @Id
  private Long id;


  @ManyToOne
  @JoinTable(name="job_workers", 
    joinColumns={@JoinColumn(name="worker_id", insertable=false,updatable=false)},
    inverseJoinColumns={@JoinColumn(name="job_id", insertable=false,updatable=false)})
  private Job job;

}