[英]Java JPA: Select 'ATTRIBUTE is in List<>'
I am using JPA and trying to select all childentities ( Product
) of a given List
of parents ( Category
). 我正在使用JPA并尝试选择给定父母
List
( Category
)的所有子项( Product
)。 The relationship is Category OneToMany Product
. 关系是
Category OneToMany Product
。 I would like to keep it down to one query and not create a Predicate
like product.get("category") == category.get(0) || product.get("category") == category.get(1) || ...
我想将其简化为一个查询,而不创建像
product.get("category") == category.get(0) || product.get("category") == category.get(1) || ...
这样的Predicate
product.get("category") == category.get(0) || product.get("category") == category.get(1) || ...
product.get("category") == category.get(0) || product.get("category") == category.get(1) || ...
. product.get("category") == category.get(0) || product.get("category") == category.get(1) || ...
I have tried the following bit of code, but this does not seem to work (as seen in the stack at the bottom). 我已经尝试了以下代码,但这似乎不起作用(如底部的堆栈所示)。 Does anyone have a suggestion as how to accomplish this?
有没有人建议如何做到这一点?
Code 码
public List<Product> findProductsBy(List<Category> categories) {
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Product> query = cb.createQuery(Product.class);
Root product = query.from(Product.class);
Predicate predicateCategory = product.get("category").in(categories);
query.select(product).where(predicateCategory);
return em.createQuery(query).getResultList();
}
Stack 堆
WARNING: Local Exception Stack:
Exception [EclipseLink-6075] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.QueryException
Exception Description: Object comparisons can only use the equal() or notEqual() operators. Other comparisons must be done through query keys or direct attribute level comparisons.
Expression: [
Relation operator [ IN ]
Query Key category
Base (...).Product
What you can do is using the category id instead of the category object (as the error state: object comparison is not supported ): 您可以使用类别ID代替类别对象(因为错误状态: 不支持对象比较 ):
(Assuming your category id is a Long
, you can do the following.) (假设您的类别ID是
Long
,则可以执行以下操作。)
public List<Product> findProductsBy(List<Category> categories) {
List<Long> categoryIds = new ArrayList<Long>();
for(Category category:categories){
categoryIds.add(category.getId());
}
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Product> query = cb.createQuery(Product.class);
Root product = query.from(Product.class);
Predicate predicateCategory = product.get("categoryId").in(categoryIds);
query.select(product).where(predicateCategory);
return em.createQuery(query).getResultList();
} }
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