public PageInfo findByPage(PageVO page) {
    PageHelper.startPage(page.getPageNum(), page.getPageSize());
    List<Project> all = projectMapper.findByPage();//分页SQL方法
    return new PageInfo<>(all);//返回
}

public PageInfo findAll(PageVO page) {
    PageHelper.startPage(page.getPageNum(), page.getPageSize()).doCount(
        () -> projectMapper.doCount() //自定义查询总数量方法,这里的返回值要求是long
    );
    List<Project> all = projectMapper.findAll();
    return new PageInfo<>(all);
}

public PageInfo findByPage(PageVO page) {
    PageHelper.startPage(page.getPageNum(), page.getPageSize()).doCount(new ISelect() {
        @Override
        public void doSelect() {
            logn count = projectMapper.doCount();//自定义查询总数量方法,这里的返回值要求是long
        }
    });
    List<Project> all = projectMapper.findByPage();
    return new PageInfo<>(all);
}

@Select("SELECT COUNT(id) FROM `project`")
long doCount();