如何使用JPA CriteriaQuery在子類屬性上進行搜索？

Question

我正在嘗試編寫一個查詢來搜索不在其超類中的子類屬性，並返回超類的所有對象。目前，當我嘗試並執行person.get（「specialAttribute」）時，我得到一個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

按照提供的提示解決了我自己的問題here。

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") 
     ) 
);