使用PageHelper分页的问题

向右看齐 2022-05-22 00:47 265阅读 0赞

今天遇到这样个问题，利用PageHelper做分页，结果查出来的pagesize和total一样，这样前端总会查到一页，这与结果不符。  
源码如下：

PageHelper.startPage(pageNum, pageSize,true);
            List<StudentScoreCollectEntity> studentScoreEntities = studentScoreCollectDao.selectByExample(studentScoreCollectExample);
            if (CollectionUtils.isEmpty(studentScoreEntities)) {
    
                logger.error("调用本服务查询学生补考成绩为空");
                return new PageInfo<>();
            }
            List<String> studentIdList = new ArrayList<>();
            for (StudentScoreCollectEntity studentScoreEntity : studentScoreEntities) {
                String studentId = studentScoreEntity.getStudentId();
                studentIdList.add(studentId);
            }
    
            List<StudentModel> studentModels = studentFacade.queryStudentBasicInfoByIds(studentIdList);
            if (CollectionUtils.isEmpty(studentModels)) {
    
                logger.error("调用基础服务查询学生信息为空");
                return new PageInfo<>();
            }
    
            List<FailExamStudentModel> failExamStudentModels = publicMethod(studentScoreEntities, studentModels);
    
            PageInfo<FailExamStudentModel> pageInfo = new PageInfo<>(failExamStudentModels);

查两个接口，然后两个返回值通过publicMethod()拼接在一起，再对该返回值做分页转换。

走断点调试发现，可能和PageHelper.startPage(pageNum, pageSize,true);放的位置有关，上网查了查，都说这句要放在查询结果list之前，它只对紧接着操作数据库的代码起作用。  
      于是试着将PageHelper.startPage(pageNum, pageSize,true);移动位置，结果查的还是不对。  
      最后试了一种方法，赋值。  
      前两个接口返回值条数一样多，干脆就将total赋值。代码修改如下：

PageHelper.startPage(pageNum, pageSize,true);
            List<StudentScoreCollectEntity> studentScoreEntities = studentScoreCollectDao.selectByExample(studentScoreCollectExample);
            PageInfo<StudentScoreCollectEntity> sscPage = new PageInfo<>(studentScoreEntities);
            if (CollectionUtils.isEmpty(studentScoreEntities)) {
    
                logger.error("调用本服务查询学生补考成绩为空");
                return new PageInfo<>();
            }
            List<String> studentIdList = new ArrayList<>();
            for (StudentScoreCollectEntity studentScoreEntity : studentScoreEntities) {
                String studentId = studentScoreEntity.getStudentId();
                studentIdList.add(studentId);
            }
    
            List<StudentModel> studentModels = studentFacade.queryStudentBasicInfoByIds(studentIdList);
            if (CollectionUtils.isEmpty(studentModels)) {
    
                logger.error("调用基础服务查询学生信息为空");
                return new PageInfo<>();
            }
    
            List<FailExamStudentModel> failExamStudentModels = publicMethod(studentScoreEntities, studentModels);
    
            PageInfo<FailExamStudentModel> pageInfo = new PageInfo<>(failExamStudentModels);
            //赋值
            pageInfo.setPageNum(pageNum);
            pageInfo.setPageSize(pageSize);
            pageInfo.setTotal(sscPage.getTotal());

暂时没想出其他更好的办法，如果您有不同建议，欢迎提出！

**感谢您的阅读！**