数据库连接池

计算确定数据表一共分几页：101/pageSize=100/10=10页。rows = select count(1) from users;方法１：pageCount = rows/pageSize + (rows%pageSize==0?0:1); 方法２：pageCount = (rows+ (pageSize-1))/(pageSize);public void doGet(HttpServletRequest req,

 计算确定数据表一共分几页：
	101/pageSize=100/10=10页。
	rows = select count(1) from users;
	方法１：pageCount = rows/pageSize + (rows%pageSize==0?0:1);
　　方法２：pageCount = (rows+ (pageSize-1))/(pageSize);
public void doGet(HttpServletRequest req, HttpServletResponse response)
			throws ServletException, IOException {
		//第一步：定义每页显示多少行
		int pageSize = 10;
		try{
			//第二步：获取数据表中有多少行
			QueryRunner run = new QueryRunner(DataSourceUtils.getDatasSource());
			String sql = "select count(*) from users";
			Object o = run.query(sql,new ScalarHandler());
			int rows = Integer.parseInt(o.toString());
			//第三步：计算一共分多少页
			int pageCount= rows/pageSize+(rows%pageSize==0?0:1);
			//将页数放到req
			req.setAttribute("pageCount",pageCount);
			
		}catch(Exception e){
			e.printStackTrace();
		}
		//转发到
		req.getRequestDispatcher("/jsps/show.jsp").forward(req, response);
		
	}
  

第四步：分析limit的开始位置

用户请求的面码

start

算法：

Limit 0,pageSize

Start

= (currentPage-1)*pageSize

Limit 10,pageSize

Limit 20,pageSize

第五步：对分页以后页码再分页

每个页面，最多显示10个页码

pageNum=10;

startNo

endNo

当前页码

页码范围

算法

1

1~10

If(currentPage

1~10

2

3

4

5

6

2~11

6-4=2 =

6-(pageNum/2-1)=2 = startNo

endNo = startNo+(pageNum-1)=11

7

3~12

8

4~13

9

10

11

11-4 = 7

endNo = 7+9=16

endNo = 11;

startNo = 2 = endNo-(pageNum-1);

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