分頁顯示對於數據在頁面中的展示是非常重要的工具，當數據條數較多時，就需要使用分頁來顯示。實現分頁顯示的思路包括：
- 確定數據庫中一共有多少條數據，即數據總數；
- 設定每頁准備顯示多少條數據，計算出一共需要分多少頁，即分頁數目=數據總數/每頁數目，當數據總數能被每頁數目整除時，就正好那么多頁；當不能整除時就要在分頁數目上再加上一頁；
- 有了數據總數，每頁數據條數、分頁數目后，開始使用數據庫查詢出每頁的數據，然后傳遞給Servlet處理，接着在視圖層顯示。
- 其中數據總數通過數據庫查詢獲得，每頁顯示數據條數，需要直接給定值，獲取每頁的數據使用sql語句的"select * from user order by ID desc limit 每頁數目*當前頁數，每頁數目", 包括兩個變量：每頁數目，這是可以直接賦值的，當前頁數，則需要從前端jsp頁面獲取才行。
下面以一個實例，說明分頁顯示實現過程：
（1）先保證數據庫里的表數據條目較多，比如本案例中學生用戶表一共8個用戶數據，每頁顯示3條，因此這里就需要3頁顯示。每頁數目=3；數據總數則需要查詢獲取。
（2）新建兩個實體：User和Page，User用於學生對象，Page用於分頁對象。
package com.student.entity; public class User { private int ID; private String Name; private String Sex; public User(int iD) { this.ID = iD; } public User(int iD, String name, String sex) { this.ID = iD; this.Name = name; this.Sex = sex; } public int getID() { return ID; } public void setID(int iD) { ID = iD; } public String getName() { return Name; } public void setName(String name) { Name = name; } public String getSex() { return Sex; } public void setSex(String sex) { Sex = sex; } }
package com.student.entity; public class Page { private int pageSize; private int totalPage; private int Index; public int getPageSize() { return pageSize; } public void setPageSize(int pageSize) { this.pageSize = pageSize; } public int getTotalPage() { return totalPage; } public void setTotalPage(int totalPage) { this.totalPage = totalPage; } public int getIndex() { return Index; } public void setIndex(int index) { this.Index = index; } public Page() { super(); } public Page(int Index, int pageSize) { this.Index = Index; this.pageSize = pageSize; } }
（3）根據需求編寫學生用戶、分頁接口及其實現類，習慣上接口命名為IName，實現類命名為NameImpl
分頁接口類：
1 package com.student.dao; 2 3 public interface IpageDao { 4 public int getTotalPage(int pageSize); 5 }
分頁實現類：
package com.student.dao; import java.sql.SQLException; public class PageDaoImpl implements IpageDao { @Override public int getTotalPage(int pageSize) { // 總共多少頁數 DButil db = new DButil(); int total = 0, totalPage = 0; String sql = "select count(ID) from user"; try { total = db.getTotalCount(sql); // 總數 totalPage = total % pageSize > 0 ? total / pageSize + 1 : total / pageSize; // 總頁數 } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } // 總數量 return totalPage; } }
用戶接口類：
package com.student.dao; import java.util.List; import org.student.entity.Page; import org.student.entity.User; public interface IUser { public List<User> queryUserByPage(Page page); }
用戶實現類，實現分頁查詢獲得每頁的數據，關鍵參數給定就是當前頁數和每頁數目：
package com.student.dao; import java.sql.*; import java.util.*; import org.student.entity.Page; import org.student.entity.User; public class UserDaoImpl implements IUser { public Connection con = null; public PreparedStatement pst = null; public Statement sm = null; public ResultSet rs = null; @Override public List<User> queryUserByPage(Page page) throws SQLException { List<User> arr = new ArrayList(); DButil db = new DButil(); // 實例化數據庫db try { con = db.initConnection(); // 連接數據庫 String sql1 = "select * from user limit ?,? "; // 分頁查詢 pst = con.prepareStatement(sql1); pst.setInt(1, page.getIndex() * page.getPageSize()); // 當前頁*每頁數目 pst.setInt(2, page.getPageSize());// 每頁數目 rs = pst.executeQuery(); while (rs.next()) { User stu = new User(rs.getInt(1), rs.getString(2), rs.getString(3));// 查詢數據存到user對象 arr.add(stu);// 存成List集合 } } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } db.close();// 關閉數據庫 return arr; } }
（4）userPageServlet代碼
@WebServlet("/userPageServlet" )
public class userPageServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
System.out.println("welcome");
//獲取當前頁數，首次進入時start為0，點擊超鏈接時獲取start頁數
int start=request.getParameter("start")==null?0:Integer.parseInt(request.getParameter("start"));
//通過page實現類獲得總頁數，這里的3為每頁數目
int pageSize=3;
PageDaoImpl pg=new PageDaoImpl();
int totalPage=pg.getTotalPage(pageSize);
//前一頁頁數、后一頁變量值
int prePage=start-1>0?start-1:start+1;
int nextPage=start+1<totalPage?start+1:totalPage-1;
//使用request.setAttribute方法便於頁面中使用el語法
request.setAttribute("totalPage", totalPage);
request.setAttribute("prePage", prePage);
request.setAttribute("nextPage", nextPage);
//獲得當前頁的數據
Page pg1=new Page(start,pageSize);
UserDaoImpl user=new UserDaoImpl();
try {
List<User> currentUser=(List<User>)user.queryUserByPage(pg1);
request.setAttribute("userList", currentUser);
request.getRequestDispatcher("userPage.jsp").forward(request, response);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
（6）前段jsp代碼
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" import="java.util.*" import="com.student.entity.User" import="com.student.entity.Page"%> <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Insert title here</title> </head> <body> <h4>所有用戶列表</h4> <table border="1" width="60%"> <tr> <td>用戶姓名</td> <td>用戶性別</td> <td>操作</td> </tr> <% request.setCharacterEncoding("UTF-8"); List<User> currentUser = (List<User>) request.getAttribute("userList"); //遍歷顯示 for (User userlist : currentUser) { %> <tr> <td><%=userlist.getName()%></td> <td><%=userlist.getSex()%></td> <td><a href="deleteStudent.jsp?ID=<%=userlist.getID()%>">刪除</a><br> <a href="updateStudent.jsp?ID=<%=userlist.getID()%>">修改</a></td> </tr> <% } %> </table> <nav> <ul class="pagination"> <li><a href="userPageServlet?start=0"> <span>首頁</span> </a></li> <li><a href="userPageServlet?start=${requestScope.prePage }"> <span>前一頁</span> </a></li> <li><a href="userPageServlet?start=${requestScope.nextPage }"> <span>后一頁</span> </a></li> <li><a href="userPageServlet?start=${requestScope.totalPage-1} "> <span>尾頁</span> </a></li> </ul> </nav> </body> </html>