JPA的上次更新时间戳 [英] Last update timestamp with JPA

问题描述

我正在玩JPA（Eclipselink具体）。下面的实体有一个
时间戳，它应该反映每次该实体最后一次更新。

I'm playing around a bit with JPA(Eclipselink to be specific). The below entity have a timestamp that's supposed to reflect whenever that entity was last updated.

每次$每次自动生成时间戳的JPA更新策略是什么b $ b这个实体被改变了吗？

What are the strategies for making JPA update that timestamp automatically every time this entity is changed ?

如果我还想要一个'创建'时间戳，我将如何进行，只有在实体第一次持久化时设置，永远不允许是否会再次更改？

How would I go about if I also want a 'creation' timestamp, only set when the entity is first persisted, never allowed to be changed again ?

 @Entity
 public class Item implements Serializable {
     private static final long serialVersionUID = 1L;
     private Integer id;
     private String note;


    public Item () {
    }


    @Id
    @GeneratedValue(strategy=SEQUENCE)
    @Column(unique=true, nullable=false)
    public Integer getId() {
        return this.id;
    }

    public void setId(Integer id) {
        this.id = id;
    }


    @Column(length=255)
    @Column(nullable=false)
    public String getNote() {
        return this.note;
    }

    public void setNote(String note) {
        this.note = note;
    }

    @Column(nullable=false)
    public Timestamp getUpdated() {
        return this.updated;
    }

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


}

推荐答案

使用 @PrePersist 和 @PreUpdate 注释并撰写你自己的事件监听器。

Use @PrePersist and @PreUpdate annotations and write your own event listener.

看看这个答案了解详情。它被标记为Hibernate，但适用于任何JPA提供商。

Take a look at this answer for details. It's tagged as Hibernate but is applicable to any JPA provider.

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