Jpa 条件查询选择联接
我需要帮助在条件查询中转换此JPQL查询:Jpa 条件查询选择联接,jpa,eclipselink,jpql,criteria-api,Jpa,Eclipselink,Jpql,Criteria Api,我需要帮助在条件查询中转换此JPQL查询: SELECT u.documentList FROM Unit u WHERE u.id = :id 这就是我尝试过的: CriteriaQuery<Document> query = builder.createQuery(Document.class); Root<Unit> root = query.from(Unit.class); Join<Unit, Document> join = root.join
SELECT u.documentList FROM Unit u WHERE u.id = :id
这就是我尝试过的:
CriteriaQuery<Document> query = builder.createQuery(Document.class);
Root<Unit> root = query.from(Unit.class);
Join<Unit, Document> join = root.join(Unit_.documentList);
query.select(join);
query.where(builder.equal(root.get(AbstractEntity_.id), entity.getId()));
以下是映射:
@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class Unit extends NamedEntity
{
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "DOCUMENT_RELATION", joinColumns = @JoinColumn(name = "PARENT_ID"), inverseJoinColumns = @JoinColumn(name = "CHILD_ID"))
protected List<Document> documentList = new ArrayList<>();
}
找到的解决方案:
CriteriaQuery<Document> query = builder.createQuery(Document.class);
Root<Unit> root = query.from(Unit.class);
root.alias("root");
Root<Document> relation = query.from(Document.class);
relation.alias("relation");
query.select(relation);
query.where
(
builder.equal(root.get(AbstractEntity_.id), item.getId()),
builder.isMember(relation, root.get(Unit_.actionList))
);
CriteriaQuery=builder.createQuery(Document.class);
Root=query.from(Unit.class);
root.别名(“root”);
根关系=query.from(Document.class);
关系。别名(“关系”);
查询、选择(关系);
请问,在哪里
(
builder.equal(root.get(AbstractEntity.id),item.getId()),
builder.isMember(关系,根.get(单元\操作列表))
);
JPA规范禁止您尝试实现的内容。单值路径表达式在select子句中有效,但集合值路径表达式无效。见规范第4.8章。我引用了专业JPA书籍:
以下查询是非法的:
选择d.employees
来自d部门
这同样适用于条件查询。为什么不直接查询单元
并调用getDocumentList()
编辑:
您还可以尝试反向查询:
SELECT d FROM Document d WHERE d.unit.id=:id
谢谢,我将检查规范。我尝试这样做是因为我需要通过JSF/PrimeFaces启用对关系集合的分页、过滤和排序。其中一些集合可能包含数千个元素,因此这也是一个性能问题。谢谢,我找到了解决方法:
SELECT d FROM Unit u,Document d WHERE d member of u.documentList
CriteriaQuery<Document> query = builder.createQuery(Document.class);
Root<Unit> root = query.from(Unit.class);
root.alias("root");
Root<Document> relation = query.from(Document.class);
relation.alias("relation");
query.select(relation);
query.where
(
builder.equal(root.get(AbstractEntity_.id), item.getId()),
builder.isMember(relation, root.get(Unit_.actionList))
);
SELECT d FROM Document d WHERE d.unit.id=:id