JSP新闻系统之七 分页实现简化版

package com.news.util;

/**
 * 有了记录总条数后，页面控制类；
 * 根据总记录数，每页显示条数，来得到总页数;
 * @author Administrator
 *
 */
public class PageControler {
	public int getTotalPages(int count,int pageSize){
		int totalPages=0;
		//如果总记录数除以每页显示条数，能够整除;
		//总页数就是它们的商，否则为商+1
		if(count%pageSize==0){
			totalPages=count/pageSize;
		}else{
			totalPages=count/pageSize+1;
		}
		return totalPages;
	}
}

UserDao中的抽象方法
//通过查询获取数据表中数据总条数;
	public int getCount();
	//根据当前页码和页数，来分页的方法;返回User集合;
	public ListqueryUserByPage(int currentPage,int pageSize);

//UserDaoImpl实现类中的方法
/* 获得user的总个数,即要分页的总记录数
	 * @see com.news.dao.UserDao#getCount()
	 */
	@Override
	public int getCount() {
		Connection con=null;
		Statement st=null;
		ResultSet rs=null;
		int count=0;
		
		try {
			con=DaoFactory.getConnection();
			st=con.createStatement();
			String sql="select count(*) from t_user";
			rs=st.executeQuery(sql);
			if(rs.next()){
				count=rs.getInt(1);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			DaoFactory.closeAll(rs, st, con);
		}
		return count;
	}


	@Override
	public ListqueryUserByPage(int currentPage, int pageSize) {
		Connection con=null;
		Statement st=null;
		ResultSet rs=null;
		Listusers=null;
		
		try {
			con=DaoFactory.getConnection();
			st=con.createStatement();
			users=new ArrayList();
			String sql="select top "+pageSize+" * from t_user where id not in (select top "+(currentPage-1)*pageSize+" id from t_user order by id)order by id";
			rs=st.executeQuery(sql);
			//遍历结果集
			while(rs.next()){
				//从数据库中取出一条记录后，放到实体对象中;
				User user=new User();
				user.setId(rs.getInt("id"));
				user.setUsername(rs.getString("username"));
				user.setEmail(rs.getString("email"));
				user.setAddress(rs.getString("address"));
				user.setHobby(rs.getString("hobby"));
				//将实体对象放入集合中;
				users.add(user);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			DaoFactory.closeAll(rs, st, con);
		}
		return users;
	}

show_user.jsp页面代码如下

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ page import="com.news.dao.*,com.news.dao.impl.*,com.news.entity.*,com.news.util.*" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

My JSP 'index.jsp' starting page=用户列表<%
   		//获取当前页码，如果获取不到，默认是第一页;
   		String pageIndex=request.getParameter("pageIndex");
   		if(pageIndex==null){
   			pageIndex="1";
   		}
   		int currentPage=Integer.parseInt(pageIndex);
   		int pageSize=4;
   		UserDao ud=new UserDaoImpl();
   		PageControler pc=new PageControler();
   		int count=ud.getCount();
   		//获得总页数;
   		int totalPages=pc.getTotalPages(count,pageSize);
   		//分页查询，得到当前页数数据;
   		Listusers=ud.queryUserByPage(currentPage,pageSize);
   		for(int i=0;i<%
  		}
  	 %>
		
			
			
				
				
					
					
						编号
					

					
						账号
					

					
						密码
					

					
						邮箱
					

					
						住址
					

					
						爱好
					

				

				
					
					
						<%=user.getId() %>
					

					
						<%=user.getUsername() %>
					

					
						<%=user.getPwd() %>
					

					
						<%=user.getEmail() %>
					

					
						<%=user.getAddress() %>
					

					
						<%=user.getHobby() %>
					

				

				
					
					
						第<%=currentPage %>页/共<%=totalPages %>页 首页 <% 
  	 			if(currentPage>1){
  	 		 %> 上一页|| <%
  	 		 	}
  	 		 	if(currentPage 下一页||
  	 		  <%} %> 末页