Java 设置要由数据库生成的 JPA 时间戳列？
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Setting a JPA timestamp column to be generated by the database?
提问by James McMahon
In my SQL Server 2000 database, I have a timestamp (in function not in data type) column of type DATETIMEnamed lastTouchedset to getdate()as its default value/binding.
在我的 SQL Server 2000 数据库中，我有一个DATETIME名为lastTouched设置getdate()为默认值/绑定类型的时间戳（在函数中不是数据类型）列。
I am using the Netbeans 6.5 generated JPA entity classes, and have this in my code
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
@Basic(optional = false)
@Column(name = "LastTouched")
@Temporal(TemporalType.TIMESTAMP)
private Date lastTouched;
However when I try to put the object into the database I get,
但是，当我尝试将对象放入数据库时，我得到了，
javax.persistence.PersistenceException: org.hibernate.PropertyValueException: not-null property references a null or transient value: com.generic.Stuff.lastTouched
I've tried setting setting the @Basicto (optional = true), but that throws an exception saying the database doesn't allow nullvalues for the TIMESTAMPcolumn, which it doesn't by design.
我试过将设置设置@Basic为(optional = true)，但这会引发一个异常，指出数据库不允许列的null值TIMESTAMP，这不是设计的。
ERROR JDBCExceptionReporter - Cannot insert the value NULL into column 'LastTouched', table 'DatabaseName.dbo.Stuff'; column does not allow nulls. INSERT fails.
I previously got this to work in pure Hibernate, but I have sense switched over to JPA and have no idea how to tell it that this column is suppose to be generated on the database side. Note that I am still using Hibernate as my JPA persistence layer.
我以前让它在纯 Hibernate 中工作，但我感觉切换到 JPA 并且不知道如何告诉它这个列应该是在数据库端生成的。请注意，我仍然使用 Hibernate 作为我的 JPA 持久层。
采纳答案by James McMahon
I fixed the issue by changing the code to
我通过将代码更改为
@Basic(optional = false)
@Column(name = "LastTouched", insertable = false, updatable = false)
@Temporal(TemporalType.TIMESTAMP)
private Date lastTouched;
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.
因此在生成 SQL 插入时忽略时间戳列。不确定这是否是解决此问题的最佳方法。欢迎反馈。
回答by Matt Luongo
I realize this is a bit late, but I've had success with annotating a timestamp column with
我意识到这有点晚了，但我已经成功地用
@Column(name="timestamp", columnDefinition="TIMESTAMP DEFAULT CURRENT_TIMESTAMP")
This should also work with CURRENT_DATEand CURRENT_TIME. I'm using JPA/Hibernate with Oracle, so YMMV.
这也应该适用于CURRENT_DATE和CURRENT_TIME。我在 Oracle 中使用 JPA/Hibernate，所以 YMMV。
回答by willtardy
I have this working well using JPA2.0 and MySQL 5.5.10, for cases where I only care about the last time the row was modified. MySQL will create a timestamp on first insertion, and every time UPDATE is called on the row. (NOTE: this will be problematic if I cared whether or not the UPDATE actually made a change).
我使用 JPA2.0 和 MySQL 5.5.10 运行良好，对于我只关心最后一次修改行的情况。MySQL 将在第一次插入时创建一个时间戳，并且每次在行上调用 UPDATE。（注意：如果我关心 UPDATE 是否实际进行了更改，这将是有问题的）。
The "timestamp" column in this example is like a "last-touched" column.x`
此示例中的“时间戳”列就像“最后触摸”列.x`
The code below uses a separate column "version" for optimistic locking.
下面的代码使用单独的列“版本”进行乐观锁定。
private long version;
private Date timeStamp
@Version
public long getVersion() {
return version;
}
public void setVersion(long version) {
this.version = version;
}
// columnDefinition could simply be = "TIMESTAMP", as the other settings are the MySQL default
@Column(name="timeStamp", columnDefinition="TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP")
@Temporal(TemporalType.TIMESTAMP)
public Date getTimeStamp() {
return timeStamp;
}
public void setTimeStamp(Date timeStamp) {
this.timeStamp = timeStamp;
}
(NOTE: @Version doesn't work on a MySQL "DATETIME" column, where the attribute type is "Date" in the Entity class. This was because Date was generating a value down to the millisecond, however MySQL was not storing the millisecond, so when it did a comparison between what was in the database, and the "attached" entity, it thought they had different version numbers)
（注意：@Version 不适用于 MySQL 的“DATETIME”列，其中实体类中的属性类型为“Date”。这是因为 Date 生成了一个精确到毫秒的值，但是 MySQL 没有存储毫秒，所以当它比较数据库中的内容和“附加”实体时，它认为它们有不同的版本号）
From the MySQL manual regarding TIMESTAMP:
With neither DEFAULT nor ON UPDATE clauses, it is the same as DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP.
回答by GlenPeterson
I do not think that every database has auto-update timestamps (e.g. Postgres). So I've decided to update this field manually everywhere in my code. This will work with every database:
我不认为每个数据库都有自动更新时间戳（例如 Postgres）。所以我决定在我的代码中的任何地方手动更新这个字段。这将适用于每个数据库：
thingy.setLastTouched(new Date());
HibernateUtil.save(thingy);
There are reasons to use triggers, but for most projects, this is not one of them. Triggers dig you even deeper into a specific database implementation.
使用触发器是有原因的，但对于大多数项目来说，这不是其中之一。触发器可以让您更深入地了解特定的数据库实现。
MySQL 5.6.28 (Ubuntu 15.10, OpenJDK 64-Bit 1.8.0_66) seems to be very forgiving, not requiring anything beyond
MySQL 5.6.28 (Ubuntu 15.10, OpenJDK 64-Bit 1.8.0_66) 似乎非常宽容，不需要任何超出
@Column(name="LastTouched")
MySQL 5.7.9 (CentOS 6, OpenJDK 64-Bit 1.8.0_72) only works with
MySQL 5.7.9（CentOS 6，OpenJDK 64 位 1.8.0_72）仅适用于
@Column(name="LastTouched", insertable=false, updatable=false)
not:
不是：
FAILED: removing @Temporal
FAILED: @Column(name="LastTouched", nullable=true)
FAILED: @Column(name="LastTouched", columnDefinition="TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP")
My other system info (identical in both environments)
我的其他系统信息（在两种环境中相同）
- hibernate-entitymanager 5.0.2
- hibernate-validator 5.2.2
- mysql-connector-java 5.1.38
- 休眠实体管理器 5.0.2
- 休眠验证器 5.2.2
- mysql-connector-java 5.1.38
回答by maximus
回答by immanuelRocha
@Column(name = "LastTouched", insertable = false, updatable = false, columnDefinition = "TIMESTAMP default getdate()")
@Temporal(TemporalType.TIMESTAMP)
private Date LastTouched;`enter code here`
回答by Nithin Poosarla
This worked for me:
这对我有用：
@Column(name = "transactionCreatedDate", nullable = false, updatable = false, insertable = false, columnDefinition = "TIMESTAMP DEFAULT CURRENT_TIMESTAMP")
回答by Dhwanil Patel
@CreationTimestamp
@Column(name="timestamp", nullable = false, updatable = false, insertable = false)
private Timestamp timestamp;
回答by ponder275
If you mark your entity with @DynamicInserte.g.
如果你用@DynamicInsert例如标记你的实体
@Entity
@DynamicInsert
@Table(name = "TABLE_NAME")
public class ClassName implements Serializable {
Hibernate will generate SQL without nullvalues. Then the database will insert its own default value. This does have performance implications See [Dynamic Insert][1].
Hibernate 将生成没有null值的SQL 。然后数据库将插入它自己的默认值。这确实会影响性能 请参阅 [动态插入] [1]。
回答by Mandeep Singh Gill
This also works for me:-
这也适用于我：-
@Temporal(TemporalType.TIMESTAMP)
@Column(name = "CREATE_DATE_TIME", nullable = false, updatable = false, insertable = false, columnDefinition = "TIMESTAMP DEFAULT CURRENT_TIMESTAMP")
public Date getCreateDateTime() {
return createDateTime;
}
public void setCreateDateTime(Date createDateTime) {
this.createDateTime = createDateTime;
}
