PageHelper在springboot中的使用方式

<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper-spring-boot-starter</artifactId>
    <version>${pagehelper.version}</version>
</dependency>

pagehelper:
  helper-dialect: mysql
  reasonable: true
  support-methods-arguments: true
  params: count=countsql

PageHelper.startPage(1,5);
//紧跟着的第一个select 方法会被分页
List list = countryMapper.findAll();

private void selectAllUsers(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {

        String num=request.getParameter("num");

        if(null==num)
        {
            num="1";
        }

        // Page PageInfo

        Page<?> page=PageHelper.startPage(Integer.parseInt(num),5);  //设置第几条记录开始，多少条记录为一页

        //通过userService获取user的信息，其sql语句为"select * from user" 但因pagehelp已经注册为插件，所以pagehelp会在原sql语句上增加limit，从而实现分页
        List<Person> persons=userService.getAllUsersBypageHelper();  //因而获得的是分好页的结果集
         
        PageInfo<?> pageHelper=page.toPageInfo(); //获取页面信息的对象，里面封装了许多页面的信息 如：总条数，当前页码，需显示的导航页等等
           request.setAttribute("persons",persons);     request.setAttribute("pagehelper",pageHelper);
       request.getRequestDispatcher("/persons.jsp").forward(request,response);

    }

 public PageResult<List<ProjectListVO>> queryByProjectName(Integer pageNo, Integer pageSize, String projectName) {
        PageResult<List<ProjectListVO>> result = new PageResult<>();
        try {
            PageHelper.startPage(pageNo, pageSize);
            List<ProjectListVO> projectVOList = projectMapper.queryByProjectName(projectName); //设置完上边的PageHelper之后查询的时候，查询语句会自动加入 limits startpage   count,查询结果就是正确的结果
            PageInfo<ProjectListVO> pageInfo = new PageInfo<>(projectVOList);
            result.setTotal(pageInfo.getTotal());
            result.setPages(pageInfo.getPages());
            result.setCurrent(pageInfo.getPageNum());
            result.setSize(pageInfo.getPageSize());
            result.setResult(projectVOList);
            result.success("查询成功！");
        } finally {
            PageHelper.clearPage();
        }

        return result;
    }

public class PageInfo implements Serializable {
private static final long serialVersionUID = 1L;
//当前页
private int pageNum;
//每页的数量
private int pageSize;
//当前页的数量
private int size;
//由于startRow 和endRow 不常用，这里说个具体的用法
//可以在页面中"显示startRow 到endRow 共size 条数据"
//当前页面第一个元素在数据库中的行号
private int startRow;
//当前页面最后一个元素在数据库中的行号
private int endRow;
//总记录数
private long total;
//总页数
private int pages;
//结果集
private List list;
//前一页
private int prePage;
//下一页
private int nextPage;
//是否为第一页
private boolean isFirstPage = false;
//是否为最后一页
private boolean isLastPage = false;
//是否有前一页
private boolean hasPreviousPage = false;
//是否有下一页
private boolean hasNextPage = false;
//导航页码数
private int navigatePages;
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//所有导航页号
private int[] navigatepageNums;
//导航条上的第一页
private int navigateFirstPage;
//导航条上的最后一页
private int navigateLastPage;
}

    @ApiOperation("根据项目名查询项目信息")
    @RequestMapping(value = "/queryByProjectName", method = RequestMethod.GET)
    public PageResult<List<ProjectListVO>> queryByProjectName(@RequestParam(defaultValue = "1", value = "pageNo") Integer pageNo,
                                                              @RequestParam(defaultValue = "10", value = "pageSize") Integer pageSize,
                                                              @RequestParam(name = "projectName") String projectName) {
        if (StringUtils.isEmpty(projectName)) {
            throw new DareException("参数错误！");
        }
        PageResult<List<ProjectListVO>> result = new PageResult<>();
        try {
            projectName = "%" + projectName + "%";
//            System.out.println(projectName);
            result = projectService.queryByProjectName(pageNo, pageSize, projectName);
        } catch (Exception e) {
            e.printStackTrace();
            log.error(e.getMessage());
            result.setSuccess(false);
            result.setMessage("操作失败！");
        }
        return result;
    }