超类的JPA 2 Criteria查询属性

Question

我有两个实体：

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class Person implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "GEN_Person")
    @SequenceGenerator(name = "GEN_Person", sequenceName = "seq_person" , initialValue = 1, allocationSize = 10)
    @Column(nullable = false)
    private Long id;
    private String familienname;
    private String vorname;

    ...
}

和子类：

@Entity
@DiscriminatorValue(value = "KIND")
public class Kind extends Person implements Serializable {
     ... // other properties
}

我想通过jpa 2中的条件查询找到所有种类的实体。

我的查询：

public List<Kind> find(String f_name, String v_name) {
    CriteriaBuilder       cb         = em.getCriteriaBuilder();
    CriteriaQuery<Kind> cq         = cb.createQuery(Kind.class);
    EntityType<Kind>    type       = em.getMetamodel().entity(Kind.class);
    Root<Kind>          kindRoot = cq.from(Kind.class);

// Constructing list of parameters
List<Predicate> predicates = new ArrayList<Predicate>();

if ((null != f_name) &&!f_name.isEmpty()) {
    predicates.add(cb.like(cb.lower(kindRoot.get(type.getDeclaredSingularAttribute("familienname",
            String.class))), "%" + f_name.toLowerCase() + "%"));
}

if ((null != v_name) &&!v_name.isEmpty()) {
    predicates.add(cb.like(cb.lower(kindRoot.get(type.getDeclaredSingularAttribute("vorname",
            String.class))), "%" + v_name.toLowerCase() + "%"));
}

cq.select(kindRoot).where(predicates.toArray(new Predicate[] {}));

    return (List<Kind>) em.createQuery(cq).getResultList();
}

但是我得到这样的错误：

     javax.ejb.EJBException: EJB Exception: ; nested exception is: 
        java.lang.IllegalArgumentException: The declared attribute [familienname] from the managed type [EntityTypeImpl@441955560:Kind [ javaType: class com.itech_progress.kiwi.entities.Kind descriptor: 
RelationalDescriptor(com.itech_progress.kiwi.entities.Kind --> [DatabaseTable(PERSON), DatabaseTable(KIND)]), mappings: 19]] is not present - however, it is declared on a superclass.;

在这种情况下，我如何建立类型查询标准查询？

Answer 1

我建议生成规范元模型（链接是 Hibernate 文档，但是 JPA 的概念）。那么就Kind_.familienname可以直接在查询中使用，因为Kind_继承familienname自Person_.

如果这不是一个选项，则应通过超类的元模型引用超类的属性：

EntityType<Person> metamodelPerson = em.getMetamodel().entity(Person.class);
...
metamodelPerson.getDeclaredSingularAttribute("familienname", String.class)