JPA级联 设置内容
你知道为什么这个：
class Owner {
@OneToMany(mappedBy = "owner",
cascade = CascadeType.ALL)
public Set<Storage> storages
...
class Storage {
@ManyToOne
public Owner owner
...
不能按预期工作：
Storage s = new Storage("S1")
Owner o = new Owner("O1")
o.storages.add(s)
...
em.persistAndFlush(o)
...
s = Storage.get...
assert(s.owner != null, "Storage does not have an Owner")
o = Order.get...
assert(!o.storages.isEmpty, "Owner does not have any Storage")
测试失败：
[info] - Storage *** FAILED ***
[info] Storage does not have an Owner
我该如何修复它？
Do you know why this:
class Owner {
@OneToMany(mappedBy = "owner",
cascade = CascadeType.ALL)
public Set<Storage> storages
...
class Storage {
@ManyToOne
public Owner owner
...
doesn't work as expected:
Storage s = new Storage("S1")
Owner o = new Owner("O1")
o.storages.add(s)
...
em.persistAndFlush(o)
...
s = Storage.get...
assert(s.owner != null, "Storage does not have an Owner")
o = Order.get...
assert(!o.storages.isEmpty, "Owner does not have any Storage")
The test fails:
[info] - Storage *** FAILED ***
[info] Storage does not have an Owner
How can I fix it?
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这个问题每 2 天被问一次。 JPA 使用双向关联的拥有方来了解关联是否存在。拥有方是没有 no
mappedBy属性的一方。因此，要告诉 JPA 所有者和存储之间存在关联，您必须设置存储的所有者：This question gets asked once every 2 days. JPA uses the owning side of a bidirectional association to know if an association exists. The owning side is the side where there is no
mappedByattribute. So, to tell JPA that an association exists between owner and storage, you must set the owner of the storage: