Mybatis-plus在新增或修改时如何自动插入或修改某个字段值

@TableName(value = "article")
@Data
public class Article implements Serializable {
    /**
     * id
     */
    @TableId(type = IdType.ASSIGN_UUID)
    private String id;
    /**
     * 图片地址
     */
    private String pictureUrl;
    /**
     * 标题
     */
    private String title;
    /**
     * 创建时间
     */
    @TableField(fill = FieldFill.INSERT)
    private String createTime;
    /**
     * 修改时间
     */
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private String updateTime;

    /**
     * 创建人
     */
    @TableField(fill = FieldFill.INSERT)
    private String createUser;

    @TableField(exist = false)
    private static final long serialVersionUID = 1L;
}

@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
    @Override
    public void insertFill(MetaObject metaObject) {
        this.setFieldValByName("createTime", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()), metaObject);
        this.setFieldValByName("updateTime", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()), metaObject);    
        this.setFieldValByName("createUser", currrentUser.getNickname(), metaObject);
    }

    @Override
    public void updateFill(MetaObject metaObject) {
        this.setFieldValByName("updateTime", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()), metaObject);

    }
}