快捷導(dǎo)航

JavaWeb分頁的實(shí)現(xiàn)代碼實(shí)例

更新時(shí)間：2019年12月25日 09:05:40 作者：RooK13

這篇文章主要介紹了JavaWeb分頁的實(shí)現(xiàn)代碼實(shí)例,文中通過示例代碼介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值,需要的朋友可以參考下

分頁的分類

分頁的實(shí)現(xiàn)分為真分頁和假分頁兩種。

1.真分頁（物理分頁）：

實(shí)現(xiàn)原理： SELECT * FROM xxx [WHERE...] LIMIT ?, 10;

第一個(gè)參數(shù)是開始數(shù)據(jù)的索引位置

10是要查詢多少條數(shù)據(jù)，即每頁顯示的條數(shù)

優(yōu)點(diǎn)：不會(huì)造成內(nèi)存溢出

缺點(diǎn)：翻頁的速度比較慢

2.假分頁（邏輯分頁）：

實(shí)現(xiàn)原理：一次性將所有的數(shù)據(jù)查詢出來放在內(nèi)存之中，每次需要查詢的時(shí)候就直接從內(nèi)存之中去取出相應(yīng)索引區(qū)間的數(shù)據(jù)

優(yōu)點(diǎn)：分頁的速度比較快

缺點(diǎn)：可能造成內(nèi)存溢出

分頁的一些術(shù)語：

-- 數(shù)據(jù)總條數(shù)： totalCount ： select count(1) from t_user;
-- 每頁顯示條數(shù)：pageSize
-- 總頁數(shù)：totalPage
-- 當(dāng)前頁：currPage
-- 起始索引： startIndex

-- 通過當(dāng)前頁碼查詢第幾頁的數(shù)據(jù)

select * from t_user limit 0, 5; -- 頁碼 1
select * from t_user limit 5, 5; -- 頁碼 2
select * from t_user limit 10, 5; -- 頁碼 3

-- 公式：startIndex = (currPage - 1) * pageSize

-- 計(jì)算一共有多少頁

-- 方法一：result = totalCount%pageSize，如果余數(shù)result為0，

-- totalPage = totalCount / pageSize

-- 如果余數(shù)result不為0，

-- totalPage = totalCount / pageSize + 1;

-- 方法二：totalPage = (totalCount + pageSize - 1) / pageSize

Pageing工具類

public class PaginationBean<T> {
  
  private List<T> dataList;
  
  private int currPage;
  
  private int totalPage;

  public List<T> getDataList() {
    return dataList;
  }

  public void setDataList(List<T> dataList) {
    this.dataList = dataList;
  }

  public int getCurrPage() {
    return currPage;
  }

  public void setCurrPage(int currPage) {
    this.currPage = currPage;
  }

  public int getTotalPage() {
    return totalPage;
  }

  public void setTotalPage(int totalPage) {
    this.totalPage = totalPage;
  }
}

Servlet

@WebServlet("/showUserList")
public class ShowUserListServlet extends HttpServlet implements Servlet {
  
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    request.setCharacterEncoding("UTF-8");
    String operation = request.getParameter("operation");
    String currPageStr = request.getParameter("currPage");
    int currPage = 0;
    
    IUserService userSevice = new UserServiceImpl();
    int totalPage = userSevice.getTotalPage();
    
    if ("首頁".equals(operation) || operation == null || currPageStr == null || currPageStr.length() == 0) {
      
      currPage = 1;
    } else if ("上一頁".equals(operation)) {
      
      currPage = Integer.parseInt(currPageStr) - 1;
      if (currPage <= 0) {
        currPage = 1;
      }
    } else if ("下一頁".equals(operation)) {
      
      currPage = Integer.parseInt(currPageStr) + 1;
      if (currPage >= totalPage) {
        currPage = totalPage;
      }
    } else {
      
      currPage = totalPage;
    }
    
    List<TestUserBean> userList = userSevice.getUserListByCurrPage(currPage);
    
    PaginationBean<TestUserBean> pageBean = new PaginationBean<TestUserBean>();
    pageBean.setDataList(userList);
    pageBean.setCurrPage(currPage);
    pageBean.setTotalPage(totalPage);
    
    request.setAttribute("page", pageBean);
    
    request.getRequestDispatcher("/userList.jsp").forward(request, response);
  }

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doGet(request, response);
  }

}

jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
  pageEncoding="UTF-8"%>
<%-- 引入JSTL --%>  
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<style>
  table {
    border-collapse: collapse;
  }
</style>
</head>
<body>
  <table border="1">
    <tr>
      <th>ID</th>
      <th>姓名</th>
      <th>密碼</th>
      <th>身份證號(hào)</th>
    </tr>
    <c:forEach items="${page.dataList }" var="user">
      <tr>
        <td>${user.id }</td>
        <td>${user.name }</td>
        <td>${user.pwd }</td>
        <td>${user.idCard }</td>
      </tr>
    </c:forEach>
  </table>
  <span>第${page.currPage }頁/共${page.totalPage }頁</span>
  <br>
  <br>
  <form action="showUserList" method="get">
    <input type="submit" name="operation" value="首頁">
    <input type="submit" name="operation" value="上一頁">
    <input type="submit" name="operation" value="下一頁">
    <input type="submit" name="operation" value="尾頁">
    
    <input type="hidden" name="currPage" value="${page.currPage }">
  </form>
</body>
</html>

以上就是本文的全部內(nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

您可能感興趣的文章: