Question

我有两个实体，ShoppingCart和ShoppingCartLine。 ShoppingCart有一系列ShoppingCartLines。我正在尝试使用条件创建JPA查询，以获取ShoppingCart ID的列表以及每个ShoppingCart拥有的ShoppingCartLines的数量。

以下是ShoppingCart类中的映射：

@OneToMany(mappedBy = "shoppingCart", fetch = FetchType.EAGER, cascade = CascadeType.ALL, orphanRemoval=true)
private Set<ShoppingCartLine> shoppingCartLines = new TreeSet<ShoppingCartLine>();

以下是我尝试使用以下代码创建JPA查询的代码：

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Tuple> cq = cb.createTupleQuery();
Root<ShoppingCart> carts = cq.from( ShoppingCart.class );
Join<ShoppingCart, ShoppingCartLine> lines = carts.join( "shoppingCartLines", JoinType.LEFT);
cq.multiselect( carts.<Long>get( "id" ), cb.count( lines ));
cq.groupBy( carts.<Long>get("id") );

Query tq = em.createQuery( cq );
return tq.getResultList();

当我运行这个时，我得到一个SQLGrammerException，生成的SQL对我来说看起来不正确。

select
    shoppingca0_.id as col_0_0_,
    count(.) as col_1_0_ 
from
    SHOPPINGCART shoppingca0_ 
left outer join
    SHOPPINGCARTLINE shoppingca1_ 
        on shoppingca0_.id=shoppingca1_.shoppingCart_id,
    SHOPPINGCARTLINE shoppingca2_ 
where
    shoppingca0_.id=shoppingca2_.shoppingCart_id 
group by
    shoppingca0_.id

我应该提到我正在使用带有MySQL5Dialect的Hibernate 3.5.4

这是我想要生成的查询：

select
    sc.id,
    count(scl.id)
from
    shoppingcart sc
left join
    shoppingcartline scl
on
    scl.shoppingCart_id = sc.id
group by
    sc.id

知道我做错了什么吗？感谢。

Answer 1

尝试用

替换连接和多选线

SetJoin<ShoppingCart, ShoppingCartLine> lines = 
    carts.joinSet( "shoppingCartLines", JoinType.LEFT);
cq.multiselect( carts.<Long>get( "id" ), cb.count( lines.<Long>get( "id" ) ));

JPA 2标准 - 分组和计数

1 个答案: