java如何实现分页查询_java分页计算页数

package cn.com.servlet;
import java.io.IOException;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import cn.com.gj.Person_info;
import cn.com.lf.JdbcUtils;
public class Personnel_definition extends HttpServlet {
/**
* 
*/
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);	
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//查询数据库里面数据的总条数
//1.数据库里面数据的总条数；
int countpage=0;
String sql0="select * from person_info";	
ResultSet rs0=JdbcUtils.select(sql0, null);
try {
while(rs0.next()){
countpage++; 
}
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
//每页显示多少行
int limt=10;
//2.如果一页是10条数据的话，那么就是all页
int all=(countpage/limt)+1;
//这个是从前台获取的数据，是上一页还是下一页
int cpage=0;
//这个是上一页还是下一页的数据
String currentpage=request.getParameter("currentpage");
if(currentpage==null||currentpage==""){
cpage=1; 
}
else{
cpage=Integer.parseInt(currentpage);
//如果到了最后一页，用户再点击下一页的时候跳转到第一页
if(cpage==(all+1)){
cpage=1; 
//如果到了第一页，用户再点击下一页的时候跳转到最后一页
}else if(cpage==0){cpage=18;}
}
//3.开始查询的数据
int start=limt*(cpage)-9;
//4.结束查询的数据
int end=limt*cpage;
//这个代码是查询数据库里面的person_info，然后循环遍历显示在页面上
//sql语句的意思就是limit 索引,显示索引以后多少行
String sql="select * from person_info limit ?,?";	
//如果到了最后一页的时候，
if(end>countpage){
limt=countpage-start+1;
}
int sz[]={start,limt};
ResultSet rs=JdbcUtils.selectint(sql, sz);
ArrayList<Person_info> list=new ArrayList<Person_info>();
try {
while(rs.next()){
//把获取的值放在pi里面，再把pi放在集合里面
Person_info pi=new Person_info(rs.getString(1), rs.getString(2), rs.getString(3), rs.getString(4), rs.getString(5), rs.getString(6));
list.add(pi);
}
request.setAttribute("list", list);
request.setAttribute("cpage", "尾页");	
request.setAttribute("cpage", cpage);
request.setAttribute("all", all);
request.getRequestDispatcher("Personnel_definition.jsp").forward(request, response);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}