如果我们在方法中使用@Transactional， @CreationTimestamp和@UpdateTimestamp将值保存在DB中，但在使用save(…)后将返回null。

在这种情况下，使用saveAndFlush(…)达到了目的

如果你正在使用会话API，根据这个答案，PrePersist和PreUpdate回调将不起作用。

我在我的代码中使用Hibernate会话的persist()方法，所以我能做到这一点的唯一方法是使用下面的代码和下面的这篇博客文章(也在答案中发布)。

@MappedSuperclass
public abstract class AbstractTimestampEntity {

    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "created")
    private Date created=new Date();

    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "updated")
    @Version
    private Date updated;

    public Date getCreated() {
        return created;
    }

    public void setCreated(Date created) {
        this.created = created;
    }

    public Date getUpdated() {
        return updated;
    }

    public void setUpdated(Date updated) {
        this.updated = updated;
    }
}

谢谢所有帮助过我的人。在我自己做了一些研究之后(我是问这个问题的人)，以下是我发现最有意义的:

Database column type: the timezone-agnostic number of milliseconds since 1970 represented as decimal(20) because 2^64 has 20 digits and disk space is cheap; let's be straightforward. Also, I will use neither DEFAULT CURRENT_TIMESTAMP, nor triggers. I want no magic in the DB. Java field type: long. The Unix timestamp is well supported across various libs, long has no Y2038 problems, timestamp arithmetic is fast and easy (mainly operator < and operator +, assuming no days/months/years are involved in the calculations). And, most importantly, both primitive longs and java.lang.Longs are immutable—effectively passed by value—unlike java.util.Dates; I'd be really pissed off to find something like foo.getLastUpdate().setTime(System.currentTimeMillis()) when debugging somebody else's code. The ORM framework should be responsible for filling in the data automatically. I haven't tested this yet, but only looking at the docs I assume that @Temporal will do the job; not sure about whether I might use @Version for this purpose. @PrePersist and @PreUpdate are good alternatives to control that manually. Adding that to the layer supertype (common base class) for all entities, is a cute idea provided that you really want timestamping for all of your entities.

只是强调一下:java.util. calendar不是用于时间戳的。date是指时间上的某一刻，不受时区等区域性事物的影响。大多数数据库以这种方式存储数据(即使它们看起来不是这样;这通常是客户端软件中的时区设置;数据是好的)

现在还有@CreatedDate和@LastModifiedDate注解。

= > https://programmingmitra.blogspot.fr/2017/02/automatic-spring-data-jpa-auditing-saving-CreatedBy-createddate-lastmodifiedby-lastmodifieddate-automatically.html

(Spring框架)

我们也遇到过类似的情况。我们使用的是Mysql 5.7。

CREATE TABLE my_table (
        ...
      updated_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
    );

这对我们很管用。