分页的分类
分页的实现分为真分页和假分页两种。
1.真分页（物理分页）：
- 实现原理：
SELECT * FROM xxx [WHERE...] LIMIT ?, 10;
第一个参数是开始数据的索引位置
10是要查询多少条数据，即每页显示的条数 - 优点： 不会造成内存溢出
- 缺点： 翻页的速度比较慢
2.假分页（逻辑分页）：
- 实现原理： 一次性将所有的数据查询出来放在内存之中，每次需要查询的时候就直接从内存之中去取出相应索引区间的数据
- 优点： 分页的速度比较快
- 缺点： 可能造成内存溢出
分页的一些术语：
-- 数据总条数： totalCount ： select count(1) from t_user;
-- 每页显示条数：pageSize
-- 总页数：totalPage
-- 当前页：currPage
-- 起始索引： startIndex
-- 通过当前页码查询第几页的数据
select * from t_user limit 0, 5; -- 页码 1
select * from t_user limit 5, 5; -- 页码 2
select * from t_user limit 10, 5; -- 页码 3
-- 公式：startIndex = (currPage - 1) * pageSize
-- 计算一共有多少页
-- 方法一：result = totalCount%pageSize，如果余数result为0，
-- totalPage = totalCount / pageSize
-- 如果余数result不为0，
-- totalPage = totalCount / pageSize + 1;
-- 方法二：totalPage = (totalCount + pageSize - 1) / pageSize
Pageing工具类
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 ("首页".equals(operation) || operation == null || currPageStr == null || currPageStr.length() == 0) {
currPage = 1;
} else if ("上一页".equals(operation)) {
currPage = Integer.parseInt(currPageStr) - 1;
if (currPage <= 0) {
currPage = 1;
}
} else if ("下一页".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>密码</th>
<th>身份证号</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 }页/共${page.totalPage }页</span>
<br>
<br>
<form action="showUserList" method="get">
<input type="submit" name="operation" value="首页">
<input type="submit" name="operation" value="上一页">
<input type="submit" name="operation" value="下一页">
<input type="submit" name="operation" value="尾页">
<input type="hidden" name="currPage" value="${page.currPage }">
</form>
</body>
</html>
原文地址：https://www.cnblogs.com/rookie97/p/12081485.html
时间： 2024-10-16 13:15:19