mybatis update语句成功后，返回指定的字段
	mapper---------------------------------------将 keyColumn 属性的 num 映射到 YourBean 中的num属性
	<update id="upt">
        <selectKey resultType="java.lang.Integer" keyColumn="num" keyProperty="num" order="AFTER">
            SELECT (SELECT num FROM your_table WHERE id = #{id}) goodsNum from DUAL
        </selectKey>
        UPDATE your_table SET num = num + #{num} WHERE id = #{id}
    </update>
	
	dao------------------------------------------传参要用 YourBean 不是(@Param("num") Integer num)
	Integer upt(YourBean yourBean);
		
	service--------------------------------------
	@Transactional(rollbackFor = Exception.class)
	public void uptSome(YourBean yourBean) {
		yourMapper.upt(yourBean);
		//**
		if (!ObjectUtils.isEmpty(yourBean.getNum()) && yourBean.getNum() <= 0) {
			throw new RuntimeException("xxxx数量不足");
		}
	}
	
	bean-----------------------------------------
	@Setter
	@Getter
	public class YourBean implements Serializable {
    private static final long serialVersionUID = 1L;

		@NotNull(message = "id为空", groups = UpdateGroup.class)
		private Long id;
		
		@NotNull(message = "数量为空", groups = {AddGroup.class, UpdateGroup.class})
		private Integer num;
		
	}