如何通过两个字段加入(CriteriaBuilder)
Posted
技术标签:
【中文标题】如何通过两个字段加入(CriteriaBuilder)【英文标题】:How to join by two fields (CriteriaBuilder) 【发布时间】:2014-07-24 05:59:36 【问题描述】:我有一个实体
@Entity
@Table(name = "`petition`")
@Getter
@Setter
public class Petition extends Auditable
private static final long serialVersionUID = -3234225397035713824L;
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "petition_selected_school", joinColumns =
@JoinColumn(name = "petition_id", nullable = false, updatable = false),
inverseJoinColumns = @JoinColumn(name = "school_id",
nullable = false, updatable = false))
private List<School> selectedSchools;
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "petition_basic_school", joinColumns =
@JoinColumn(name = "petition_id", nullable = false, updatable = false),
inverseJoinColumns = @JoinColumn(name = "school_id",
nullable = false, updatable = false))
private List<School> fullBasicSchoolList;
我想通过标准构建器构建这样的 SQL 选择
SELECT DISTINCT
p.id
FROM petition p JOIN petition_selected_school s ON p.id = s.petition_id
LEFT JOIN petition_basic_school b ON p.id = b.petition_id AND s.school_id = b.school_id
WHERE b IS NULL
ORDER BY p."id" ASC
我试过这个:
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<Petition> criteriaQuery = builder.createQuery(Petition.class);
Root root = criteriaQuery.from(Petition.class);
criteriaQuery.distinct(true);
Join join = root.join("selectedSchools");
Join join2 = root.join("fullBasicSchoolList", JoinType.LEFT,);
Predicate p = builder.equal(join2.get("school"),join.get("school"));
finalPredicateList.add(p);
criteriaQuery = criteriaQuery.where(builder.and(finalPredicateList.toArray(new Predicate[finalPredicateList.size()])));
但是生成的sql是这样的:
SELECT DISTINCT
petition0_.id AS col_0_0_
FROM "petition" petition0_ INNER JOIN petition_selected_school selectedsc1_ ON petition0_.id = selectedsc1_.petition_id
INNER JOIN "school" school2_ ON selectedsc1_.school_id = school2_.id
LEFT OUTER JOIN petition_basic_school fullbasics3_ ON petition0_.id = fullbasics3_.petition_id
LEFT OUTER JOIN "school" school4_ ON fullbasics3_.school_id = school4_.id
WHERE petition0_.id = 245 AND school4_.school = school2_.school
主要问题是“如何不仅通过一个参数加入”?
p.id = b.petition_id AND s.school_id = b.school_id
【问题讨论】:
【参考方案1】:您使用的是什么版本的 JPA?
在 JPA 2.1 中,您可以通过两个字段连接,只要其中一个字段通过以下方式确定关系:
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<Petition> criteriaQuery = builder.createQuery(Petition.class);
Root root = criteriaQuery.from(Petition.class);
criteriaQuery.distinct(true);
Join join = root.join("selectedSchools");
//FIRST CONDITION (BY ID)
Join join2 = root.join("fullBasicSchoolList", JoinType.LEFT,);
//NEW
join2.on([SECOND_CONDITION])
[...]
【讨论】:
以上是关于如何通过两个字段加入(CriteriaBuilder)的主要内容,如果未能解决你的问题,请参考以下文章