基于主查询 JPA Criteria 创建子查询 API
Create a subquery based on main query JPA Criteria API
我需要在 JPA 中编写与此类似的查询:
SELECT
a.id,
b.status
FROM
atable a
JOIN btable b ON a.btable_id = b.id
where
(
(
b.status = 'INITIAL'
and a.main_atable_id is null
)
or exists (
SELECT
1
FROM
atable a2
JOIN btable b2 ON a2.btable_id = b2.id
WHERE
b2.status = 'INITIAL'
and b2.main_atable_id = a.id
)
);
如您所见,atable
有一个名为 main_atable_id
的列,它创建了父子关系,其想法是有一个主版本,其子版本是重复的。
我需要构建一个与父查询几乎相同的子查询。我会手写它只是复制代码,但我想尽可能地通过重用主查询的 Specification
来保持简单。
我的主要查询现在看起来像这样:
public Page<AtableDTO> findAtables(AtableSearchDTO filter, Pageable pageable) {
Specifications<Atable> where = Specifications.where(alwaysTrue());
if(filter.getStatus() != null) {
where = where.and(statusEquals(filter.getStatus()));
}
Page<AtableDTO> resultPage = atableRepository.findAll(where, new PageRequest(pageable.getPageNumber(), pageable.getPageSize(), Sort.Direction.DESC, "id")).map(atableMapper::toDto);
}
public Specification<Atable> alwaysTrue() {
return (root, query, cb) -> cb.and();
}
public Specification<Atable> statusEquals(AtableStatus value) {
return (root, query, cb) -> cb.equal(root.get("status"), value);
}
我只需要知道:
1) 是否可以重复使用相同的 Specification
2) 如果是,你能用这个或任何其他简单的例子来演示吗
谢谢
为什么是 EXISTS
子句?您的查询相当于:
SELECT
a.id,
b.status
FROM
atable a
JOIN btable b ON a.btable_id = b.id
JOIN btable b2 ON a.btable_id = b2.id
WHERE (b.status = 'INITIAL' AND a.main_atable_id IS NULL)
OR (b2.status = 'INITIAL' AND b2.main_atable_id = a.id);
(参见 fiddle)
假设您的实体结构如下:
@Entity
public class ATable {
@Id
private Long id;
@OneToOne
@JoinColumn(name = "btable_id")
private BTable b;
@ManyToOne
@JoinColumn(name = "atable_main_id")
private ATable main;
}
@Entity
public class BTable {
@Id
private Long id;
private Status status;
@ManyToOne
@JoinColumn(name = "atable_main_id")
private ATable main;
}
您需要以下查询:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Object[]> criteria = cb.createQuery(Object[].class);
Root<ATable> a = criteria.from(ATable.class);
Join<ATable, BTable> b = a.join("b");
Join<ATable, BTable> b2 = a.join("b");
criteria.where(cb.or(
cb.and(
cb.equal(b.get("status"), cb.literal(Status.INITIAL)),
a.get("main").isNull()),
cb.and(
cb.equal(b2.get("status"), cb.literal(Status.INITIAL)),
cb.equal(b2.get("main"), a)
)));
criteria.multiselect(a.get("id"), b.get("status"));
我需要在 JPA 中编写与此类似的查询:
SELECT
a.id,
b.status
FROM
atable a
JOIN btable b ON a.btable_id = b.id
where
(
(
b.status = 'INITIAL'
and a.main_atable_id is null
)
or exists (
SELECT
1
FROM
atable a2
JOIN btable b2 ON a2.btable_id = b2.id
WHERE
b2.status = 'INITIAL'
and b2.main_atable_id = a.id
)
);
如您所见,atable
有一个名为 main_atable_id
的列,它创建了父子关系,其想法是有一个主版本,其子版本是重复的。
我需要构建一个与父查询几乎相同的子查询。我会手写它只是复制代码,但我想尽可能地通过重用主查询的 Specification
来保持简单。
我的主要查询现在看起来像这样:
public Page<AtableDTO> findAtables(AtableSearchDTO filter, Pageable pageable) {
Specifications<Atable> where = Specifications.where(alwaysTrue());
if(filter.getStatus() != null) {
where = where.and(statusEquals(filter.getStatus()));
}
Page<AtableDTO> resultPage = atableRepository.findAll(where, new PageRequest(pageable.getPageNumber(), pageable.getPageSize(), Sort.Direction.DESC, "id")).map(atableMapper::toDto);
}
public Specification<Atable> alwaysTrue() {
return (root, query, cb) -> cb.and();
}
public Specification<Atable> statusEquals(AtableStatus value) {
return (root, query, cb) -> cb.equal(root.get("status"), value);
}
我只需要知道:
1) 是否可以重复使用相同的 Specification
2) 如果是,你能用这个或任何其他简单的例子来演示吗
谢谢
为什么是 EXISTS
子句?您的查询相当于:
SELECT
a.id,
b.status
FROM
atable a
JOIN btable b ON a.btable_id = b.id
JOIN btable b2 ON a.btable_id = b2.id
WHERE (b.status = 'INITIAL' AND a.main_atable_id IS NULL)
OR (b2.status = 'INITIAL' AND b2.main_atable_id = a.id);
(参见 fiddle)
假设您的实体结构如下:
@Entity
public class ATable {
@Id
private Long id;
@OneToOne
@JoinColumn(name = "btable_id")
private BTable b;
@ManyToOne
@JoinColumn(name = "atable_main_id")
private ATable main;
}
@Entity
public class BTable {
@Id
private Long id;
private Status status;
@ManyToOne
@JoinColumn(name = "atable_main_id")
private ATable main;
}
您需要以下查询:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Object[]> criteria = cb.createQuery(Object[].class);
Root<ATable> a = criteria.from(ATable.class);
Join<ATable, BTable> b = a.join("b");
Join<ATable, BTable> b2 = a.join("b");
criteria.where(cb.or(
cb.and(
cb.equal(b.get("status"), cb.literal(Status.INITIAL)),
a.get("main").isNull()),
cb.and(
cb.equal(b2.get("status"), cb.literal(Status.INITIAL)),
cb.equal(b2.get("main"), a)
)));
criteria.multiselect(a.get("id"), b.get("status"));