java - 如何在hibernate中查找外键的id

Question

我有两个实体，即:

状态

@Entity
@Table(name = "State")
public class StateEntity {

   @Column(name = "id", length = 36, nullable = false, unique = true)
   private String id;

  @ManyToOne (fetch = FetchType.LAZY)
  @JoinColumn(name = "InsurerId", nullable = false)
  private InsurerEntity insurer;

  @Column(name ="StateName", length = 50, nullable = false)
  private String stateName;

//getters and setters

}

保险公司

@Entity
@Table(name = "Insurer")
public class InsurerEntity {

  @Column(name = "InsurerId", length = 36, nullable = false, unique = true)
  private String insurerId;

  @Column(name = "InsurerName", length = 100, nullable = true)
  private String insurerName;

  @OneToMany(mappedBy = "state", fetch = FetchType.LAZY)
  private List<StateEntity> stateEntityList;

//getters and setters

}

保险公司的 ID 保存在 state 数据库中，我想使用 hibernate 查询检索它，但我似乎找不到解决方案

如何使用 CriteriaBuilder、CriteriaQuery 和 Root 在 Hibernate 查询中编写此查询 SELECT InsurerId FROM State; ..

Answer 1

如果您想选择所有州的所有保险公司 ID:

String selectionQuery = "SELECT s.insurer.insurerId FROM State s";
List<String> insurersIds = session.createQuery(selectionQuery).list();

如果您想选择某个州的保险公司 ID:

String selectionQuery = "SELECT s.insurer.insurerId FROM State s WHERE s.id = :stateId";
String insurerId = (String) session.createQuery(selectionQuery).setParameter("stateId", stateId).getSingleResult(); //This should be placed in a try/catch block to handle org.hibernate.NonUniqueResultException

编辑:

您应该按照普拉萨德在回答中所写的那样更新您的保险公司实体。