题外话：该分页显示是用 “表示层-控制层-DAO层-数据库”的设计思想实现的，有什么需要改进的地方大家提出来，共同学习进步。

思路：首先得在 DAO 对象中提供分页查询的方法，在控制层调用该方法查到指定页的数据，在表示层通过 EL 表达式和 JSTL 将该页数据显示出来。

重点：两个方法：（1）计算总的页数。 （2）查询指定页数据。

 

1.DAO层-数据库

JDBCUtils 类用于打开和关闭数据库，核心代码如下：

1 import java.sql.Connection; 2 import java.sql.DriverManager; 3 import java.sql.PreparedStatement; 4 import java.sql.ResultSet; 5 import java.sql.SQLException; 6  7 public class JDBCUtils { 8     private Connection conn=null; 9     private PreparedStatement pstmt=null; 10     11     12     /**13      * connect 连接数据库14      * @return15      */16     public Connection connect(){17         String user="root";18         String password="1234";19         String driverClass = "com.mysql.jdbc.Driver";20         String jdbcUrl = "jdbc:mysql://localhost:3306/book";21         22         try {23             Class.forName(driverClass);24             conn = DriverManager.getConnection(jdbcUrl, user, password);25         } catch (Exception e) {26             // TODO Auto-generated catch block27             e.printStackTrace();28         }29         return conn;30         31     }32     33     /**34      * close 关闭数据库35      * @param conn36      * @param pstmt37      * @param resu38      */39     public void close(Connection conn,PreparedStatement pstmt,ResultSet result){40         if(conn != null){41             try {42                 conn.close();43             } catch (SQLException e) {44                 // TODO Auto-generated catch block45             }46         }47         if(pstmt != null){48             try {49                 pstmt.close();50             } catch (SQLException e) {51                 // TODO Auto-generated catch block52                 e.printStackTrace();53             }54         }55         if(result != null){56             try {57                 result.close();58             } catch (SQLException e) {59                 // TODO Auto-generated catch block60                 e.printStackTrace();61             }62         }63     }64 65 }

UserDao 类中的方法 getPage() 和方法 listUser() 分别用来计算总页数和查询指定页的数据，核心代码如下：

1 import java.sql.Connection; 2 import java.sql.PreparedStatement; 3 import java.sql.ResultSet; 4 import java.sql.SQLException; 5 import java.util.ArrayList; 6 import java.util.List; 7  8 import com.db.JDBCUtils; 9 10 public class UserDao {11     /**12      * 计算总的页数13      * @return14      */15     public int getPage(){16         int recordCount=0,t1=0,t2=0;17         PreparedStatement pstmt=null;18         ResultSet result=null;19         JDBCUtils jdbc=new JDBCUtils();20         Connection conn=jdbc.connect();21         String sql="select count(*) from books";22         try {23             pstmt=conn.prepareStatement(sql);24             result=pstmt.executeQuery();25             result.next();26             recordCount=result.getInt(1);27             t1=recordCount%5;28             t2=recordCount/5;29         } catch (Exception e) {30             // TODO Auto-generated catch block31             e.printStackTrace();32         }finally{33             jdbc.close(conn, pstmt, result);34         }35         if(t1 != 0){36             t2=t2+1;37         }38         39         return t2;40     }41     42     /**43      * 查询指定页的数据44      * @param pageNo45      * @return46      */47     public List
     
       listUser(int pageNo){48         PreparedStatement pstmt=null;49         ResultSet result=null;50         List
      
        list=new ArrayList
       
        ();51         int pageSize=5;52         int page=(pageNo-1)*5;53         JDBCUtils jdbc=new JDBCUtils();54         Connection conn=jdbc.connect();55         String sql="select * from books order by id limit ?,?";56         try {57             pstmt=conn.prepareStatement(sql);58             pstmt.setInt(1, page);59             pstmt.setInt(2, pageSize);60             result=pstmt.executeQuery();61             while(result.next()){62                 User user=new User();63                 user.setId(result.getInt(1));64                 user.setName(result.getString(2));65                 user.setNumber(result.getString(3));66                 list.add(user);67                 68             }69         } catch (Exception e) {70             // TODO Auto-generated catch block71             e.printStackTrace();72         }finally{73             jdbc.close(conn, pstmt, result);74         }75         return list;76     }77 78 }
       
      
     

User 类用于存储查询到的数据，核心代码如下：

1 public class User { 2     private int id; 3     private String name; 4     private String number; 5     public int getId() { 6         return id; 7     } 8     public void setId(int id) { 9         this.id = id;10     }11     public String getName() {12         return name;13     }14     public void setName(String name) {15         this.name = name;16     }17     public String getNumber() {18         return number;19     }20     public void setNumber(String number) {21         this.number = number;22     }23 }

 

2.控制层

ListUser 类内部调用 UserDao 对象查询数据并指派页面显示数据，核心代码如下：

1 import java.io.IOException; 2 import java.io.PrintWriter; 3 import java.util.ArrayList; 4 import java.util.List; 5  6 import javax.servlet.ServletException; 7 import javax.servlet.http.HttpServlet; 8 import javax.servlet.http.HttpServletRequest; 9 import javax.servlet.http.HttpServletResponse;10 11 import com.dao.User;12 import com.dao.UserDao;13 14 public class ListUser extends HttpServlet {15     public ListUser() {16         super();17     }18 19     public void destroy() {20         super.destroy(); // Just puts "destroy" string in log21         // Put your code here22     }23 24     public void doGet(HttpServletRequest request, HttpServletResponse response)25             throws ServletException, IOException {26 27         doPost(request, response);28     }29 30     public void doPost(HttpServletRequest request, HttpServletResponse response)31             throws ServletException, IOException {32 33         34         response.setCharacterEncoding("utf-8");35         int pageNo = 1;36         UserDao userdao=new UserDao();37         List
     
       lists=new ArrayList
      
       ();38         String pageno=request.getParameter("pageNos");39         if(pageno != null){40             pageNo=Integer.parseInt(pageno);41         }42         lists=userdao.listUser(pageNo);43         int recordCount=userdao.getPage();44         request.setAttribute("recordCount", userdao.getPage());45         request.setAttribute("listss", lists);46         request.setAttribute("pageNos", pageNo);47         request.getRequestDispatcher("userlist.jsp").forward(request, response);48     }49 50     public void init() throws ServletException {51         // Put your code here52     }53 54 }
      
     

 

3.表示层

输出页面 userlist.jsp ,使用 EL 和 JSTL 输出查询结果，核心代码如下：

1 <%@ page language="java" import="java.util.*"  pageEncoding="UTF-8"%> 2 <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> 3 <%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%>   4 <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%> 5 <% 6 String path = request.getContextPath(); 7 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 8 %> 9 10 11 12   13     14     15     16     17     
     18     
     19     
         20     
     21     
     22     
     25 31   32   33   34     
图书信息
35     
     
      36         
37     
      
       
        
书号
        
书名
        
库存量
       
      
     
38      
     
      40          
     
     
      39          
        41          
42          
43          
44          
45         46     
      
       
        
${person.id}
        
${person.name }
        
${person.number }
       
      
     
47      
48 49      
     
      50          
      首页51          
      上一页52      
     53      54       
     
      55          
      下一页56          
      末页57      
     58 59     
     
      60     
      
共${recordCount}页 &nbsp61     页62     63     
64      
     
65   66 

 

4.效果图