JPA条件以多对多关系查询

时间：2013-11-07 08:17:51

标签： jpa eclipselink criteria jpql criteria-api

我在EclipseLink 2.3.2中使用JPA 2.0，其中我在产品和颜色之间存在多对多的关系。产品可以具有多种颜色，并且颜色可以与许多产品相关联。这种关系在数据库中由三个表表示。

  • 产品
  • prod_colour（加入表格）
  • 颜色

prod_colour表分别来自其相关父表prod_id和colour_id的两个参考列product和colour。

很明显，实体类Product有一组颜色 - java.util.Set<Colour>，名为colourSet。

实体类Colour有一组产品 - java.util.Set<Product>，名为productSet。

我需要根据提供的colour 从prodId表中获取颜色列表，不匹配{中的颜色 {1}}表。

相应的JPQL类似于以下内容。

prod_colour

它生成以下SQL语句。

FROM Colour colour 
WHERE colour.colourId 
NOT IN(
SELECT colours.colourId 
     FROM Product product 
     INNER JOIN product.colourSet colours 
     WHERE product.prodId=:id) 
ORDER BY colour.colourId DESC

由于这又是一个运行时查询，因此最好有一个条件查询。我没有深入了解在这种复杂关系中制作标准查询。

到目前为止，我有以下查询，这与前面的JPQL完全无关。

SELECT t0.colour_id, t0.colour_hex, t0.colour_name 
FROM projectdb.colour t0 
WHERE t0.colour_id 
NOT IN (
       SELECT DISTINCT t1.colour_id 
       FROM prod_colour t3, projectdb.product t2, projectdb.colour t1 
       WHERE ((t2.prod_id = ?)
       AND ((t3.prod_id = t2.prod_id) 
       AND (t1.colour_id = t3.colour_id)))) 
ORDER BY t0.colour_id DESC

如何编写与给定的JPQL相对应的条件查询？

修改

此条件查询：

CriteriaBuilder criteriaBuilder=entityManager.getCriteriaBuilder();
CriteriaQuery<Colour>criteriaQuery=criteriaBuilder.createQuery(Colour.class);
Metamodel metamodel = entityManager.getMetamodel();
EntityType<Colour> entityType = metamodel.entity(Colour.class);
Root<Colour> root = criteriaQuery.from(entityType);
SetJoin<Colour, Product> join = root.join(Colour_.productSet, JoinType.INNER);
ParameterExpression<Long> parameterExpression=criteriaBuilder.parameter(Long.class);
criteriaQuery.where(criteriaBuilder.equal(join.get(Product_.prodId), parameterExpression));  

TypedQuery<Colour> typedQuery = entityManager.createQuery(criteriaQuery).setParameter(parameterExpression, prodId);
List<Colour> list=typedQuery.getResultList();

反过来产生以下SQL查询。

CriteriaBuilder criteriaBuilder=entityManager.getCriteriaBuilder();
CriteriaQuery<Tuple>criteriaQuery=criteriaBuilder.createQuery(Tuple.class);
Metamodel metamodel = entityManager.getMetamodel();
EntityType<Colour> entityType = metamodel.entity(Colour.class);
Root<Colour> root = criteriaQuery.from(entityType);
criteriaQuery.multiselect(root.get(Colour_.colourId));
SetJoin<Colour, Product> join = root.join(Colour_.productSet, JoinType.INNER);
ParameterExpression<Long> parameterExpression=criteriaBuilder.parameter(Long.class);
criteriaQuery.where(criteriaBuilder.equal(join.get(Product_.prodId), parameterExpression));

TypedQuery<Tuple> typedQuery = entityManager.createQuery(criteriaQuery).setParameter(parameterExpression, prodId);
List<Tuple> list = typedQuery.getResultList();

如何将此查询与子查询相关联，以便它可以生成以下SQL查询？

SELECT t0.colour_id 
FROM projectdb.colour t0, prod_colour t2, projectdb.product t1 
WHERE ((t1.prod_id = 1) 
AND ((t2.colour_id = t0.colour_id) 
AND (t1.prod_id = t2.prod_id))))

修改

以下条件查询以及SELECT t0.colour_id, t0.colour_hex, t0.colour_name FROM projectdb.colour t0 WHERE t0.colour_id NOT IN ( SELECT t0.colour_id FROM projectdb.colour t0, prod_colour t2, projectdb.product t1 WHERE ((t1.prod_id = 1) AND ((t2.colour_id = t0.colour_id) AND (t1.prod_id = t2.prod_id)))) ORDER BY t0.colour_id DESC 有效。

NOT EXISTS()

然而，它生成带有不必要/额外/冗余连接的SQL查询，如下所示（尽管它返回所需的结果集）。

CriteriaBuilder criteriaBuilder=entityManager.getCriteriaBuilder();
CriteriaQuery<Colour>criteriaQuery=criteriaBuilder.createQuery(Colour.class);
Metamodel metamodel = entityManager.getMetamodel();
EntityType<Colour> entityType = metamodel.entity(Colour.class);
Root<Colour> root = criteriaQuery.from(entityType);
criteriaQuery.select(root);
Subquery<Long>subquery=criteriaQuery.subquery(Long.class);
Root<Product> subRoot = subquery.from(Product.class);
subquery.select(root.get(Colour_.colourId));
Predicate paramPredicate = criteriaBuilder.equal(subRoot.get(Product_.prodId), prodId);
Predicate correlatePredicate = criteriaBuilder.equal(root.get(Colour_.productSet), subRoot);
subquery.where(criteriaBuilder.and(paramPredicate, correlatePredicate));
criteriaQuery.where(criteriaBuilder.exists(subquery).not());
criteriaQuery.orderBy(criteriaBuilder.desc(root.get(Colour_.colourId)));

TypedQuery<Colour> typedQuery = entityManager.createQuery(criteriaQuery);
List<Colour>list= typedQuery.getResultList();

这应该就像，

SELECT t0.colour_id, t0.colour_hex, t0.colour_name 
FROM projectdb.colour t0 
WHERE 
NOT (EXISTS (
       SELECT t0.colour_id 
       FROM prod_colour t3, projectdb.product t2, projectdb.product t1 
       WHERE (((t1.prod_id = 1) 
       AND (t1.prod_id = t2.prod_id)) 
       AND ((t3.colour_id = t0.colour_id) 
       AND (t2.prod_id = t3.prod_id)))))
ORDER BY t0.colour_id DESC

有没有办法让子查询包含SELECT t0.colour_id, t0.colour_hex, t0.colour_name FROM projectdb.colour t0 WHERE NOT (EXISTS ( SELECT t0.colour_id FROM prod_colour t3, projectdb.product t2 WHERE (((t2.prod_id = 1)) AND ((t3.colour_id = t0.colour_id) AND (t2.prod_id = t3.prod_id))))) ORDER BY t0.colour_id DESC 子句而不是NOT IN()并摆脱这种冗余连接？

此查询生成的冗余联接已报告为bug。

1 个答案:

答案 0 :(得分：2)

以下是有关NOT IN()的条件查询（但我更喜欢NOT EXISTS()而不是NOT IN()）。

CriteriaBuilder criteriaBuilder=entityManager.getCriteriaBuilder();
CriteriaQuery<Colour>criteriaQuery=criteriaBuilder.createQuery(Colour.class);
Metamodel metamodel = entityManager.getMetamodel();
EntityType<Colour> entityType = metamodel.entity(Colour.class);
Root<Colour> root = criteriaQuery.from(entityType);
criteriaQuery.select(root);

Subquery<Long>subquery=criteriaQuery.subquery(Long.class);
Root<Product> subRoot = subquery.from(Product.class);
subquery.select(root.get(Colour_.colourId));

Predicate paramPredicate = criteriaBuilder.equal(subRoot.get(Product_.prodId), prodId);
Predicate correlatePredicate = criteriaBuilder.equal(root.get(Colour_.productSet), subRoot);

subquery.where(criteriaBuilder.and(paramPredicate, correlatePredicate));
criteriaQuery.where(criteriaBuilder.in(root.get(Colour_.colourId)).value(subquery).not());
criteriaQuery.orderBy(criteriaBuilder.desc(root.get(Colour_.colourId)));

TypedQuery<Colour> typedQuery = entityManager.createQuery(criteriaQuery);
List<Colour> list=typedQuery.getResultList();

这会产生以下SQL查询。

SELECT t0.colour_id, t0.colour_hex, t0.colour_name 
FROM projectdb.colour t0 
WHERE NOT 
(t0.colour_id IN (
                 SELECT t0.colour_id 
                 FROM prod_colour t3, projectdb.product t2, projectdb.product t1 
                 WHERE (((t1.prod_id = ?) 
                 AND (t1.prod_id = t2.prod_id)) 
                 AND ((t3.colour_id = t0.colour_id) 
                 AND (t2.prod_id = t3.prod_id))))) 
ORDER BY t0.colour_id DESC

此查询返回所需的结果集。然而，它可以看到产生冗余连接，但这似乎是bug。

修改

在Hibernate上尝试the same query，编写此条件查询的方式看起来不正确。连接和子查询的组合导致生成正确的SQL查询。

CriteriaBuilder criteriaBuilder=entityManager.getCriteriaBuilder();
CriteriaQuery<Colour>criteriaQuery=criteriaBuilder.createQuery(Colour.class);
Metamodel metamodel = entityManager.getMetamodel();
EntityType<Colour> entityType = metamodel.entity(Colour.class);
Root<Colour> root = criteriaQuery.from(entityType);
criteriaQuery.select(root);

Subquery<Long>subquery=criteriaQuery.subquery(Long.class);
Root<Colour> subRoot = subquery.from(Colour.class);
subquery.select(subRoot.get(Colour_.colourId));
SetJoin<Colour, Product> join = subRoot.join(Colour_.productSet, JoinType.INNER);

ParameterExpression<Long> parameterExpression=criteriaBuilder.parameter(Long.class);
criteriaQuery.where(criteriaBuilder.in(root.get(Colour_.colourId)).value(subquery).not());
subquery.where(criteriaBuilder.equal(join.get(Product_.prodId), parameterExpression));
criteriaQuery.orderBy(criteriaBuilder.desc(root.get(Colour_.colourId)));

TypedQuery<Colour> typedQuery = entityManager.createQuery(criteriaQuery);
List<Colour> list = typedQuery.setParameter(parameterExpression, 1L).getResultList();

这会生成以下SQL查询，而后者又会委托给MySQL。

SELECT t0.colour_id, t0.colour_name, t0.colour_hex
FROM projectdb.colour t0
WHERE NOT (t0.colour_id IN 
          (SELECT t1.colour_id
           FROM prod_colour t3, projectdb.product t2, projectdb.colour t1
           WHERE ((t2.prod_id = ?)
           AND ((t3.colour_id = t1.colour_id)
           AND (t2.prod_id = t3.prod_id)))))
ORDER BY t0.colour_id DESC
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