Java对结果集List＜Object＞进行模糊查询和Page分页

浅浅的花香味﹌ 2023-10-08 17:14 40阅读 0赞

## 项目场景： ##

公司项目需要对在线用户进行管理，在线用户的ID信息存储于缓存redis，列表信息显示的时候，需要通过ID查询本地数据库获取用户信息，分页和关键字模糊查询。

--------------------

## 思路： ##

step1：获取redis中所有在线用户ID数据；  
step2：根据ID获取本地数据库的用户信息，得到List<UserDto> list结果集合；  
step3：然后通过List流的anyMatch和关键字的String的contains方法达到关键字模糊查询的效果；

step4：手动PageHelper分页显示（因为list流筛选操作了结果集List，所以PageHelper.startPage(pageIndex,pageSize)会失效，所以需要手动分页，具体原因可以看LZ另一篇PageHelper失效的帖子介绍：[点击这里][Link 1]）``

--------------------

## 开始实操： ##

> 提示：帖子标题很明确了，这里LZ只写思路step3、step4

**业务类实操显示如下：****LZ这里模糊查询了三个字段，账户、用户名和角色，模糊查询的字段越多这里代码越臃肿，这里可以****优化****封装****list.stream().anyMatch()和list.stream().filter().collect()**

@Override
        public ResponseResult getUserList(Integer pageIndex, Integer pageSize, String search) {
            //step1：
               /**
                * 省略
                */
            //step2:根据ID获取本地数据库的用户信息
            List<UserDto> list = new ArrayList<>();
            /**
              * 省略获取用户信息
              */
            //step3:关键字筛选模糊查询
            search = Optional.ofNullable(search).orElse("");//校验非空并转换空字符串
            if (list.size() > 0) {
                String finalSearch = search;
                boolean nameFlag = list.stream().anyMatch(userDto -> userDto.getUsername().contains(finalSearch));
                if (!nameFlag) {//模糊匹配字段
                    boolean serialnoFlag = list.stream().anyMatch(userDto -> userDto.getAccount().contains(finalSearch));
                    if (!serialnoFlag) {
                        boolean roleFlag = list.stream().anyMatch(userDto -> userDto.getRole().contains(finalSearch));
                        if (!roleFlag) {
                            list.clear();
                        } else {
                            list = list.stream()
                                    .filter(userDto -> userDto.getRole().contains(finalSearch))
                                    .collect(Collectors.toList());//过滤筛选信息
                        }
                    } else {
                        list = list.stream()
                                .filter(userDto -> userDto.getAccount().contains(finalSearch))
                                .collect(Collectors.toList());
                    }
                } else {
                    list = list.stream()
                            .filter(userDto -> userDto.getUsername().contains(finalSearch))
                            .collect(Collectors.toList());
                }
                //step4:手动分页
                int total = list.size(); //计算总记录数
                List<UserDto> collect = list.stream()
                        .skip((pageIndex - 1) * pageSize)
                        .limit(pageSize)
                        .collect(Collectors.toList());//pageHelper无效，流操作：skip跳记录和limit限制显示记录数
                int pageSum = total % pageSize == 0 ? total / pageSize : total / pageSize + 1;//计算总页数
                PageHelper.startPage(pageIndex, pageSize);
                PageInfo<UserDto> scorePageInfo = new PageInfo<>(collect);
                scorePageInfo.setTotal(total);//总记录数
                scorePageInfo.setPages(pageSum);//总页数
                return ResponseResult.success(scorePageInfo);
            }else {
                return ResponseResult.success(new PageInfo<>(list));
            }
        }

#### **优化代码如下：****代码层次分明，业务思路清晰（有兴趣的话可以看LZ对[七大设计原则的Java实战理解和图解][Java]）** ####

@Override
        public ResponseResult getUserList(Integer pageIndex, Integer pageSize, String search) {
            //step1：
            /**
             * 省略
             */
            //step2:根据ID获取本地数据库的用户信息
            List<UserDto> list = new ArrayList<>();
            /**
             * 省略获取用户信息
             */
            //step3:关键字筛选模糊查询
            search = Optional.ofNullable(search).orElse("");//校验非空并转换空字符串
            if (list.size() > 0) {
                String finalSearch = search;
                if (!anyMatchUser(list,finalSearch,3)) {//模糊匹配字段
                    if (!anyMatchUser(list,finalSearch,2)) {
                        if (!anyMatchUser(list,finalSearch,1)) {
                            list.clear();
                        } else {
                            list = filterUser(list,finalSearch,1);//过滤筛选信息
                        }
                    } else {
                        list =  filterUser(list,finalSearch,2);
                    }
                } else {
                    list =  filterUser(list,finalSearch,3);
                }
                //step4:手动分页
                int total = list.size(); //计算总记录数
                List<UserDto> collect = list.stream()
                        .skip((pageIndex - 1) * pageSize)
                        .limit(pageSize)
                        .collect(Collectors.toList());//pageHelper无效，流操作：skip跳记录和limit限制显示记录数
                int pageSum = total % pageSize == 0 ? total / pageSize : total / pageSize + 1;//计算总页数
                PageHelper.startPage(pageIndex, pageSize);
                PageInfo<UserDto> scorePageInfo = new PageInfo<>(collect);
                scorePageInfo.setTotal(total);//总记录数
                scorePageInfo.setPages(pageSum);//总页数
                return ResponseResult.success(scorePageInfo);
            }else {
                return ResponseResult.success(new PageInfo<>(list));
            }
        }

/**
         * list过滤用户
         * @param list
         * @param finalSearch
         * @return
         */
        private List<UserDto> filterUser(List<UserDto> list,String finalSearch,int filterType){
            if(filterType==1){
                list = list.stream()
                        .filter(userDto -> userDto.getRole().contains(finalSearch))
                        .collect(Collectors.toList());
            }else if(filterType==2){
                list = list.stream()
                        .filter(userDto -> userDto.getAccount().contains(finalSearch))
                        .collect(Collectors.toList());
            }else{
                list = list.stream()
                        .filter(userDto -> userDto.getUsername().contains(finalSearch))
                        .collect(Collectors.toList());
            }
            return list;
        }
       /**
         * list过滤匹配用户字段
         * @param list
         * @param finalSearch
         * @return
         */
        private boolean anyMatchUser(List<UserDto> list,String finalSearch,int filterType){
            boolean flag = false;
            if(filterType==1){
                flag = list.stream().anyMatch(userDto -> userDto.getRole().contains(finalSearch));
            }else if(filterType==2){
                flag = list.stream().anyMatch(userDto -> userDto.getAccount().contains(finalSearch));
            }else{
                flag = list.stream().anyMatch(userDto -> userDto.getUsername().contains(finalSearch));
            }
            return flag;
        }

> 结束语：挣钱是游戏，活着才是胜利，快乐才是真谛，健康才是目的。

[Link 1]: https://blog.csdn.net/Da_zhenzai/article/details/127864051
[Java]: https://blog.csdn.net/Da_zhenzai/article/details/126726826