如何在一次查询中获取具有所有子关联的实体？

Question

我有一个名为 Ave 的 JPA 实体，它有两个子关联，如下所示：

@Entity
@Table(name = "ave")
@Access(AccessType.FIELD)
public class Ave implements Serializable {

  @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.MERGE, targetEntity = Contact.class)
  @JoinTable(name = "ave_contact", joinColumns = @JoinColumn(name = "ave_id"), inverseJoinColumns = @JoinColumn(name = "potentialbuyer_id"))
  @Fetch(value = FetchMode.SUBSELECT)
  private List<Contact> allPotentialBuyers = new ArrayList<>();


  @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, targetEntity = Bid.class, mappedBy = "ave")
  @Fetch(value = FetchMode.JOIN)
  private Set<Bid> bids = new HashSet<>();

我想在一个 JPQL 查询中加载所有 Ave 实体，所有 bids 和所有 allPotentialBuyers（可能有多个 SQL 选择）。（怎么）可能？

Answer 1

使用left join fetch:

entityManager.createQuery(
"select a " +
"from Ave a " +
"left join fetch a.allPotentialBuyers " +
"left join fetch a.bids", Ave.class
).getResultSet();

如何在一次查询中获取具有所有子关联的实体？

How to fetch an entity with all children associations in one query?

java

sql

database

set

jpql