Java JPA：如何选择@Embeddeble类

我将从@Embeddeble Class Certification中选择所有列。但我不能选择它。如何选择可嵌入类

@Entity
public class Department implements Serializable {


  private static final long serialVersionUID = 1L;
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;
  private String name;

  @ElementCollection
  @CollectionTable(name = "Certification", joinColumns = {@JoinColumn(name="user_id")})
  private List<Certification> certifications = new ArrayList<Certification>();

  public List<Certification> getCertifications() {
      return certifications;
  }

  public void setCertifications(List<Certification> certifications) {
      this.certifications = certifications;
  }


  public String getName() {
      return name;
  }

  public void setName(String name) {
      this.name = name;
  }

  .....

如果运行ResultService，会出现以下异常：

原因：java.lang.IllegalArgumentException:在EntityManager中创建查询时发生异常： 异常说明：编译查询时出错[从证书c中选择c]。未知的实体类型[证书]

---

如何选择@Embeddeble类？

您需要通过真实实体类，即

部门

检索

认证

。一个查询示例如下：

   select cer from Department dep join dep.certifications cer

或者，您可能希望检索符合条件的部门实体，然后使用它们获取证书

   select cer from Department dep join dep.certifications cer