设置由数据库生成的 JPA 时间戳列?-Java问题

Setting a JPA timestamp column to be generated by the database?(设置由数据库生成的 JPA 时间戳列?)

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问题描述

在我的 SQL Server 2000 数据库中，我有一个名为 lastTouched 的类型为 DATETIME 的时间戳(在函数中，不在数据类型中)列设置为 getdate() 作为其默认值/绑定.

In my SQL Server 2000 database, I have a timestamp (in function not in data type) column of type DATETIME named lastTouched set to getdate() as its default value/binding.

我正在使用 Netbeans 6.5 生成的 JPA 实体类，并在我的代码中有这个

I am using the Netbeans 6.5 generated JPA entity classes, and have this in my code

@Basic(optional = false)
@Column(name = "LastTouched")
@Temporal(TemporalType.TIMESTAMP)
private Date lastTouched;

但是，当我尝试将对象放入我得到的数据库时，

However when I try to put the object into the database I get,

javax.persistence.PersistenceException: org.hibernate.PropertyValueException: not-null property references a null or transient value: com.generic.Stuff.lastTouched

我尝试将 @Basic 设置为 (optional = true)，但这会引发异常，提示数据库不允许 nullTIMESTAMP 列的 code> 值，并非设计使然.

I've tried setting the @Basic to (optional = true), but that throws an exception saying the database doesn't allow null values for the TIMESTAMP column, which it doesn't by design.

ERROR JDBCExceptionReporter - Cannot insert the value NULL into column 'LastTouched', table 'DatabaseName.dbo.Stuff'; column does not allow nulls. INSERT fails.

我以前让它在纯 Hibernate 中工作，但后来我切换到 JPA 并且不知道如何告诉它该列应该在数据库端生成.请注意，我仍然使用 Hibernate 作为我的 JPA 持久层.

I previously got this to work in pure Hibernate, but I have since switched over to JPA and have no idea how to tell it that this column is supposed to be generated on the database side. Note that I am still using Hibernate as my JPA persistence layer.

推荐答案

我通过将代码更改为解决了这个问题

I fixed the issue by changing the code to

@Basic(optional = false)
@Column(name = "LastTouched", insertable = false, updatable = false)
@Temporal(TemporalType.TIMESTAMP)
private Date lastTouched;

因此在生成 SQL 插入时会忽略时间戳列.不确定这是否是解决此问题的最佳方法.欢迎反馈.

So the timestamp column is ignored when generating SQL inserts. Not sure if this is the best way to go about this. Feedback is welcome.

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