如何使用JPA CriteriaQuery搜索子类属性？

Question

我试图编写一个查询来搜索不在其超类中的子类属性并返回超类的所有对象.目前,当我尝试执行person.get("specialAttribute")时,我得到一个NullPointerException.

@Inheritance(strategy = InheritanceType.JOINED)
@Entity
public abstract class Person {
    public String searchableAttribute;
}

@Entity
@Table( name = "normal_person" )
public class NormalPerson extends Person {

}

@Entity
@Table( name = "special_person" )
public class SpecialPerson extends Person {
    @Column(nullable = false, unique = true)
    public String specialAttribute;
}

// Controller method

    Root<Person> person = query.from(Person.class);
    query.where(
            builder.or(
                    builder.like(person.<String>get("specialAttribute"), "foo"),
                    builder.like(person.<String>get("searchableAttribute"), "foo")
            )
    );

Answer 1

按照此处提供的提示解决了我自己的问题.

Root<Person> person = query.from(Person.class);

Subquery<SpecialPerson> subQuery = query.subquery(SpecialPerson.class);
Root<SpecialPerson> specialPersonRoot = subQuery.from(SpecialPerson.class);

subQuery.select(specialPersonRoot);
subQuery.where(builder.like(specialPersonRoot.<String>get("specialAttribute"), "foo"));

query.where(
        builder.or(
                builder.in(person).value(subQuery)
                builder.like(person.<String>get("searchableAttribute"), "foo")
        )
);