java 使用 JPA 进行更新时如何排除实体字段
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How to exclude an entity field when doing an update with JPA
提问by aurelius
Is there a way to make a field non-persistent at update operation but persistent at create operation with JPA - Hibernate 4?
有没有办法使字段在更新操作时非持久化，但在使用 JPA - Hibernate 4 创建操作时持久化？
I tried it in this way
我是这样试的
@Transient
@Id
@Column(name = "USER_NAME", nullable = false, length = 75)
private String userName;
but with @Transient annotation the field will be transient across all CRUD operations and I want a way to specify that only on this operation is persistent (create).
但是使用@Transient 注释，该字段在所有 CRUD 操作中都是瞬态的，我想要一种方法来指定仅在此操作上是持久的（创建）。
Is there a way to do this?
有没有办法做到这一点？
Thanks!
谢谢！
回答by Vlad Mihalcea
As explained in this article, you need to set updatableto false:
如本文所述，您需要设置updatable为false：
@Column(name = "USER_NAME", nullable = false, length = 75, updatable= false)
private String userName;
The updatableattribute instruct Hibernate to omit this column from the generated UPDATESQL statement.
该updatable属性指示 Hibernate 从生成的UPDATESQL 语句中省略此列。
I removed the @Transientand the @Idannotations.
我删除了@Transient和@Id注释。
If this column is your PK (mapped to the entity identifier), then you can only set it during INSERT, since Hibernate doesn't allow you to update an entity identifier (the updatableattribute being redundant in this case).
如果此列是您的 PK（映射到实体标识符），那么您只能在 INSERT 期间设置它，因为 Hibernate 不允许您更新实体标识符（updatable在这种情况下该属性是多余的）。
