如何在不加载JPA中的相关实体的情况下使用外键保存实体？ [英] How do I save an entity with foreign key without loading the related entity in JPA?

问题描述

我有两个实体：

Account {
  @Id
  Long id;
}

Preference {
  ...
  @ManyToOne
  private Account account;
}

保存首选项时，我有accountId，但我没有帐户实体。在这种情况下我应该如何保存偏好？

When saving a Preference, I have the accountId, but I don't have an Account entity. How should I save the preference in this situation?

加载帐户实体并将其设置在首选项上？对我来说，这似乎是错误的数据库之旅。

Load the Account entity and set it on the preference? To me, that seems like an erroneous trip to the database.

有一个可持久的accountId字段并使Account字段为只读吗？同时拥有accountId字段和Account字段似乎是多余的？

Have an accountId field that is persistable and make the Account field read-only? Having both an accountId field and an Account field seems redundant?

使用NamedQuery来保留首选项？我希望通常只保存一个没有特殊逻辑的实体。

Use a NamedQuery to persist the Preference? I was hoping to just generically save an entity without special logic for.

推荐答案

使用 em.getReference（ Account.class，accountId）。它返回实体上的未初始化代理，无需转到数据库。您的用例是此方法存在的主要原因。

Use em.getReference(Account.class, accountId). It returns an uninitialized proxy on the entity, without going to the database. Your use-case is the main reason for the existence of this method.

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