[英]Criteria API (Specification JPA) Join
这是我目前的模型
@Entity
public class A {
@Id
private Long id;
String name;
...
@Entity
public class B {
@Id
private Long id;
@ManyToOne()
@JoinColumn(name = "a_id")
private A a;
@ManyToOne()
@JoinColumn(name = "c_id")
private C c;
...
@Entity
public class C {
@Id
private Long id;
private String status;
我想要一个 A 类的列表,其中 C 类的状态为“ACTIVE”,使用带有显式 JOIN 的 Criteria API作为以下示例与IN
Subquery<B> subQB = query.subquery(B.class);
Root<B> rootB = subQB.from(B.class);
subQB.select(rootB.get("c").get("id"))
.where(builder.equal(rootB.get("c").get("status"), "ACTIVE"));
predicates.add(root.get("id").in(subQB)); // root is class A
谢谢你的帮助。
如果没有实际运行的数据库,它不应该类似于
CriteriaBuilder cb = em.getCriteriaBuilder();
// Because the result is "A"
CriteriaQuery<A> q = cb.createQuery(A.class);
// Start from B
Root<B> bRoot = q.from(B.class);
// Path from B to A, as local variable to increase readability
Path<A> aPath = bRoot.get("a");
// Path from B to C and to C's status, as local variable to increase readability
Path<C> cPath = bRoot.get("c");
Path<String> cStatusPath = cPath.get("status");
// SELECT A FROM B WHERE B.C.Status = "ACTIVE"
q.select(aPath)
.where(cb.equal(cStatusPath, "ACTIVE"));
编辑:
显式连接应该与第一个解决方案非常相似,所以
CriteriaBuilder cb = em.getCriteriaBuilder();
// Because the result is "A"
CriteriaQuery<A> q = cb.createQuery(A.class);
// Start from B
Root<B> bRoot = q.from(B.class);
// Path from B to A, as local variable to increase readability
Path<A> aPath = bRoot.get("a");
// Join from B to C and to C's status, as local variable to increase readability
Join<B, C> cJoin = bRoot.join("c");
Path<String> cStatusPath = cJoin.get("status");
// SELECT A FROM B WHERE B.C.Status = "ACTIVE"
q.select(aPath)
.where(cb.equal(cStatusPath, "ACTIVE"));
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