springboot使用mybatis-plus表单更新null值问题通用解决方案

问题背景

使用mybatis-plus进行数据库交互，默认开启null不更新设置，在新增数据后，编辑页面将字段值清除后（date类型，int类型，为避免默认值传入，model全部使用包装类型初始化为null）无法将null值更新至数据库

单个解决方案

通过UpdateWrapper的set方法强制字段为null值

通用解决方法

定义基础类BaseModel，增加属性updateFieldList，model继承此类

public class BaseModel {
    @TableField(exist = false)
    @JSONField(serialize = false)
    private List<String> updateFieldList;

    public List<String> getUpdateFieldList() {
        return updateFieldList;
    }

    public void setUpdateFieldList(List<String> updateFieldList) {
        this.updateFieldList = updateFieldList;
    }
}

自定自定义注解UpdateRequestBody替代RequestBody

    @ResponseBody
    @PostMapping("/update")
    public Object update(@UpdateRequestBody AccountDO entity) {
        Result result = null;
        try {
            accountService.update(entity);
            result = Result.okResult();
        } catch (Exception e) {
            result = Result.errorResult();
        }
        return result;
    }

    @ResponseBody
    @PostMapping("/batchUpdate")
    public Object batchUpdate(@UpdateRequestBody List<AccountDO> entityList) {
        Result result = null;
        try {
            accountService.batchUpdate(entityList);
            result = Result.okResult();
        } catch (Exception e) {
            result = Result.errorResult();
        }
        return result;
    }

自定义HandlerMethodArgumentResolver对前台json至后台Model转换的拦截，需要对List类型的Model集合进行支持，获取前台提交json对应定义Model中有同名属性的，进行加入打待更新字段列表updateFieldList

public class BaseModelMethodArgumentResolver implements HandlerMethodArgumentResolver {
    @Override
    public boolean supportsParameter(MethodParameter methodParameter) {
        if (methodParameter.hasParameterAnnotation(UpdateRequestBody.class)) {
            //集合
            if(List.class.isAssignableFrom(methodParameter.getParameterType())){
                ParameterizedType parameterizedType = (ParameterizedType) methodParameter.getGenericParameterType();
                Class clazz = (Class)parameterizedType.getActualTypeArguments()[0];
                //取出List中的真实对象类型
                if(BaseModel.class.isAssignableFrom(clazz)){
                    return true;
                }else{
                    return  false;
                }
            }else{
                //单个对象
                if(BaseModel.class.isAssignableFrom(methodParameter.getParameterType())){
                    return true;
                }else{
                    return false;
                }
            }
        }
        return false;
    }

    @Override
    public Object resolveArgument(MethodParameter methodParameter, ModelAndViewContainer modelAndViewContainer, NativeWebRequest nativeWebRequest, WebDataBinderFactory webDataBinderFactory) throws Exception {
        String body = "";
        try {
            HttpServletRequest request = nativeWebRequest.getNativeRequest(HttpServletRequest.class);
            body = CommonUtil.getBodyString(request);
        } catch (Exception e) {
            e.printStackTrace();
        }
        if(List.class.isAssignableFrom(methodParameter.getParameterType())){
            List resultList = new ArrayList();
            ParameterizedType parameterizedType = (ParameterizedType) methodParameter.getGenericParameterType();
            Class clazz = (Class)parameterizedType.getActualTypeArguments()[0];
            List<Field> fs = Arrays.asList(clazz.getDeclaredFields());
            JSONArray array = JSONArray.parseArray(body);
            for (Object temp:array) {
                JSONObject obj = JSONObject.parseObject(temp.toString());
                List<String> updateFieldList = new ArrayList<>();
                for (String key : obj.keySet()) {
                    for (Field filed : fs) {
                        if (key.toLowerCase().equals(filed.getName().toLowerCase())) {
                            updateFieldList.add(key.toLowerCase());
                            continue;
                        }
                    }
                }
                obj.put("updateFieldList",updateFieldList);
                resultList.add(obj);
            }
            return  JSONArray.parseArray(resultList.toString(),clazz);
        }else{
            Class clazz = methodParameter.getParameterType();
            List<String> updateFieldList = new ArrayList<>();
            List<Field> fs = Arrays.asList(clazz.getDeclaredFields());
            JSONObject obj = JSON.parseObject(body);
            for (String key : obj.keySet()) {
                for (Field filed : fs) {
                    if (key.toLowerCase().equals(filed.getName().toLowerCase())) {
                        updateFieldList.add(key.toLowerCase());
                        continue;
                    }
                }
            }
            obj.put("updateFieldList",updateFieldList);
            return JSON.parseObject(obj.toString(),clazz);
        }

    }
}

将自定义BaseModelMethodArgumentResolver 加入到配置中去

public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
        resolvers.add(new BaseModelMethodArgumentResolver());
    }
}

进行自定义UpdateWrapper构造

 public <T extends BaseModel>  UpdateWrapper getUpdateWrapper(T entity){
        UpdateWrapper<T> updateWrapper = new UpdateWrapper<T>();
        try{
           Class clazz = entity.getClass();
           List<Field> fs = Arrays.asList(clazz.getDeclaredFields());
           List<String> updateFieldList = entity.getUpdateFieldList();
           if(updateFieldList!=null){
               for (String updateFiled:updateFieldList ) {
                   for (Field field:fs) {
                       field.setAccessible(true);
                       if(field.getName().toLowerCase().equals(updateFiled)){
                           Object fieldValue = field.get(entity);
                           updateWrapper.set(fieldValue==null,field.getName(),null);
                           continue;
                       }
                   }
               }
           }
           return updateWrapper;
       }catch (Exception e){
           e.printStackTrace();
       }
        return updateWrapper;
    }

注：对标记TableField忽略注解的字段可以优化，反射可以应用初始化时扫描加入缓存进行优化