mybatis分页插件PageHelper的使用

<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper</artifactId>
<version>4.1.5</version>
</dependency>

int pageNum = 1;
int pageSize= 10;
int topN = 3;
//获取第1页，10条内容，默认查询总数count
PageHelper.startPage(pageNum , pageSize);
List<Blog> list =blogServiceImpl.getList();
PageInfo page = new PageInfo(list);
Map<String, Object> map = new HashMap<String, Object>();
map.put("page",page);
map.put("list",list);

PageHelper.startPage(pageNum , pageSize);
PageHelper.orderBy("blog_ID desc");

private int pageNum;
private int pageSize;
private int startRow;
private int endRow;
private long total;
private int pages;
private List<E> result;