JPA 检索到的对象的 id 丢失

发布于 2024-12-08 18:58:59 字数 643 浏览 0 评论 0原文

我有一个带有整数 id 字段的简单对象，如下所示：

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(unique = true, nullable = false)
private int id;

对象可以正确保存到数据库中。但是，当通过以下方式从数据库检索对象时：

EntityManagerFactory emFactory = Persistence.createEntityManagerFactory("MyService");
EntityManager entityManager = emFactory.createEntityManager();
MyObject myObject = entityManager.find(MyObject.class, 1);
entityManager.close();

检索到的对象的 id 字段始终为零，但所有其他字段的值都能正确检索。

如果我从代码中删除 @Id 注释，则可以像所有其他字段一样正确检索 id 字段的值。

我将 OpenJPA 与 MS SQL Server 2008 一起使用。MS sqljdbc 驱动程序和 JTDS 驱动程序都经过测试。

原文

I have a simple object with an integer id field as followings:

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(unique = true, nullable = false)
private int id;

Objects can be persisted into database correctly. However, when retrieving object from the database by:

EntityManagerFactory emFactory = Persistence.createEntityManagerFactory("MyService");
EntityManager entityManager = emFactory.createEntityManager();
MyObject myObject = entityManager.find(MyObject.class, 1);
entityManager.close();

The id field of a retrieved object is always zero, but values of all other fields are retrieved correctly.

If I remove the @Id annotation from the code, the value of id field can be retrieved correctly just like all other fields.

I'm using OpenJPA with MS SQL Server 2008. Both MS sqljdbc driver and JTDS driver are tested.

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