java - JPA:在保存时忽略字段，但在选择时获取

Question

我使用 Hibernate 作为我的 JPA 提供者，我希望在调用 save() 时忽略实体中的字段之一。但是，我在相应的数据库表中确实有一个匹配列，并且我希望在获取实体时用数据库值填充我的实体字段。因此，我希望在保存实体时忽略该字段，但在获取实体时不忽略。

如果我使用@Transient，该字段将被完全忽略，这不是我想要的。有什么办法吗？

Answer 1

来自优秀的书 Pro JPA 2 :

JPA defines options to set individual mappings to be read-only using the insertable and updatable elements of the @Column and @JoinColumn annotations. These two settings default to true but can be set to false if we want to ensure that the provider will not insert or update information in the table in response to changes in the entity instance. If the data in the mapped table already exists and we want to ensure that it will not be modified at runtime, then the insertable and updatable elements can be set to false, effectively preventing the provider from doing anything other than reading the entity from the database.

@Column(insertable = false, updatable = false)
private String readOnlyField;