hibernate - Hibernate - 允许引用未保存的瞬态实例

Question

我正在使用 Hibernate 保存与其他表有关系的表的记录，但我需要允许空引用，而不保存子对象。

情况是这样的：A类有相关的对象b和c，当我保存一个A实例时，我想保存b和c的空引用。

表结构如下：

id (PK) | id_tr_inner_costs | release_id | requirement_id | task_id | hours | total_cost

requirements_id 和/或 task_id 可以为空，在这种情况下应该这样设置。

可能吗？

谢谢

Answer 1

Hibernate will set those ID's to null if the references are null at the time of saving. So something like this:

A instanceOfA = ...;
instanceOfA.setRelease(null);
instanceOfA.setTask(null);
session.save(instanceOfA);

should result in you having a row in the A table that has NULL for both release_id and task_id.

This is detailed very lightly in the Hibernate docs:

With the exception of collections, all built-in Hibernate types support null semantics.

ie, if something is null in Java, then it will be null in the database.