java-jpa-specification：如何在属于嵌套对象的字段上创建标准/规范？

Question

我在我的项目中使用了JDK1.8、hibernate和jpa。并使用规范/条件构建我的搜索查询。

我有一个a类（一个hibernate实体），它有B类作为属性。所以，粗略地说，它看起来像：

@Entity
class A {
     Long id;  
     String comment;

     @OneToOne
     B b;
}

@Entity
class B {
    
     Long id;
     String type;
}


 

public interface ARepository extends PagingAndSortingRepository<A, Integer>,
                                                                    JpaSpecificationExecutor<A> {

select * from A a left join B b on a.b_id = b.id 
   where b.type='final' and a.comment='blah';

public Specification<A> getSpecification() {

return (itemRoot, query, criteriaBuilder) -> {
    .........
    List<Predicate> partialQueries = new ArrayList<>();

    partialQueries.add(criteriaBuilder.equal(itemRoot.get("b.type"), "final"));
    partialQueries.add(criteriaBuilder.equal(itemRoot.get("comment"), "blah"));

    //Other queries to be added...

    return   criteriaBuilder.and(partialQueries.toArray(new Predicate[0]));
  };
}

Unable to locate Attribute  with the the given name [b.type] on this ManagedType [com.something.domain.A]

Answer 1

如果要筛选嵌套对象。你可以写

itemRoot.get("NestedTableName").get("nestedfieldname")

In your case - itemRoot.get("B").get("type")