@PrePersist // 用于在将实体保存到数据库之前进行处理

public class MyEntity {
    @Id
    private Long id;

    @Column(name = "name")
    private String name;

    @Column(name = "created_by", updatable = false)
    private String createdBy;

    @PrePersist
    public void prePersist() {
        if (this.createdBy == null) {
            this.createdBy = "default"; // 设置默认值
        }
    }
}