Getting Hibernate to create a TIMESTAMP column

Question

I am using Hibernate 5.2.14 through Spring Boot 2.0 with MySQL 5.7.20. I am letting Hibernate generate my Schema (ddl-auto=update, I am aware to only use this during development phase) and I am unable to make Hibernate generate a TIMESTAMP column in the Schema. Things I have tried (in Kotlin):

@Column
var modifiedAt: Instant?

@Column
@Type(type = "timestamp")
var modifiedAt: Instant?

@Column
@Type(type = "Instant")
var modifiedAt: Instant?

@Column
@Temporal(TIMESTAMP)
var modifiedAt: Date?

@Column
@Type(type = "timestamp")
var modifiedAt: Date?

All these generate a DATETIME column in the database. How do I instruct Hibernate to create a TIMESTAMP column? I am aware I could use columnDefinition = "TIMESTAMP", however this is just ramming raw SQL down Hibernate's throat, which seems wrong. Is it really the only way?

diesieben07 · Accepted Answer · 2018-03-24 16:10:18Z

2

As it turns out the Hibernate people are much smarter than me and actually read the MySQL documentation- As it also turns out, TIMESTAMP in MySQL sucks, mostly for being 32-Bit and therefor susceptible to the year-2038-bug. DATETIME is therefor the lesser evil and you just need to make sure to store everything in UTC.

Link to Hibernate Forums: https://discourse.hibernate.org/t/why-does-hibernate-orm-uses-datetime-by-default-on-mysql-instead-of-timestamp/422

answered Mar 24, 2018 at 16:10

diesieben07

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Jan Vladimir Mostert · Accepted Answer · 2018-03-23 18:50:10Z

0

This is how I handle create and update timestamps.

@Column(nullable = false)
@Temporal(TemporalType.TIMESTAMP)
var created: Date = Date()

@Column(nullable = false)
@Temporal(TemporalType.TIMESTAMP)
var modified: Date = Date()

@PreUpdate
protected fun onUpdate() {
    this.modified = Date()
}

answered Mar 23, 2018 at 18:50

Jan Vladimir Mostert

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3 Comments

diesieben07 Over a year ago

You can see in my question that I already tried the java.util.Date + TemporalType.TIMESTAMP combination. Hibernate generates a DATETIME column for this as well.

Jan Vladimir Mostert Over a year ago

It does, but it doesn't update the timestamp, that's what the @PreUpdate snippet is for; that will update the timestamp of the modified field every time you persist or merge the entity.

diesieben07 Over a year ago

I know how PreUpdate and friends work. That is not my problem. I want a TIMESTAMP column, not DATETIME. DATETIME is something completely different and not at all the correct type to use for TemporalType.TIMESTAMP.

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