MyBatisPlus 不能更新null

MybatisPlus的update默认机制是更新字段时判断是否为null,做值为null,则不更新该字段
当我们需要将部分字段更新为null时,可利用UpdateWrapper解决该问题
UpdateWrapper用法

 WarehouseItem warehouseItem = warehouseItemService.getById(2117733125);
 UpdateWrapper<WarehouseItem> updateWrapper = new UpdateWrapper<>();
 //可将指定字段更新为null
 updateWrapper.set("ownerId", null); 
 updateWrapper.set("product_id",123456);
 warehouseItemService.update(warehouseItem, updateWrapper);

        //修改值
        User user = new User();
        user.setStatus(true);
        user.setName("zhangsan");
 
        //修改条件
        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper.eq("name", "lqf");
        //这个必须填写修改主键，代表修改哪条记录
        updateWrapper.eq("id",user.getId());
 
        int update = baseMapper.update(user, userUpdateWrapper);

https://blog.csdn.net/fly_or/article/details/121093337
https://blog.csdn.net/ncnhhm/article/details/129406785

	/**
	 * 附件相关
	 */
	@Schema(description="附件相关")
	@TableField(updateStrategy = FieldStrategy.IGNORED)
	private String relevantFiles;

		//1.主表
		ProProject po = new ProProject();

		//this.saveOrUpdate(po );

		//2.转map 赋值null
		
		Map<String, Object> mp = new HashMap<>();
		mp = BeanUtil.beanToMap(po);
		mp.put("taskId",null);

		//3.在转回po ，保存
		ProProject po = new ProProject();
	po = BeanUtil.toBeanIgnoreCase(mp, ProProjectTaskCompanyLaunchEntity.class, false);
		po.setApplyType(1);
		po.setStatusValue(0);
		po.setStatusName("草稿");

		this.save(po);

https://www.jb51.net/program/2963197fl.htm