SELECT COUNT(*) FROM 表名

# 第一個 ?：從哪一個索引的數(shù)據(jù)開始查詢(默認從 0 開始)
# 第二個 ?：查詢多少條數(shù)據(jù)
SELECT * FROM 表名 LIMIT ?, ?

// 優(yōu)先計算總頁數(shù)
int totalPage = rows % pageSize == 0 ? rows / pageSize : rows / pageSize + 1;
//上一頁等于當前頁-1,但不能超過1頁界限
int prevPage = currentPage - 1 >= 1 ? currentPage - 1 : 1;
//下一頁等于當前頁+1,但不能超過總頁數(shù)界限
int nextPage = currentPage + 1 <= totalPage ? currentPage + 1 : totalPage;

/**
* 封裝結果數(shù)據(jù)（某一頁的數(shù)據(jù)）
*/
@Getter
public class PageResult<T> {
?? ?// 兩個用戶的輸入
?? ?private int currentPage; // 當前頁碼
?? ?private int pageSize; // 每頁顯示的條數(shù)
?? ?// 兩條 SQL 語句執(zhí)行的結果
?? ?private int totalCount; // 總條數(shù)
?? ?private List<T> data; // 當前頁結果集數(shù)據(jù)
?? ?// 三個程序計算的數(shù)據(jù)
?? ?private int prevPage; // 上一頁頁碼
?? ?private int nextPage; // 下一頁頁碼
?? ?private int totalPage; // 總頁數(shù)/末頁頁碼
?? ?// 分頁數(shù)據(jù)通過下面構造期封裝好
?? ?public PageResult(int currentPage, int pageSize, int totalCount, List<T>
?? ?data) {
?? ??? ?this.currentPage = currentPage;
?? ??? ?this.pageSize = pageSize;
?? ??? ?this.totalCount = totalCount;
?? ??? ?this.data = data;
?? ??? ?// 計算三個數(shù)據(jù)
?? ??? ?this.totalPage = totalCount % pageSize == 0 ? totalCount / pageSize :
?? ??? ?totalCount / pageSize + 1;
?? ??? ?this.prevPage = currentPage - 1 >= 1 ? currentPage - 1 : 1;
?? ??? ?this.nextPage = currentPage + 1 <= this.totalPage ? currentPage + 1 :
?? ??? ?this.totalPage;
?? ?}
}

@Setter
@Getter
/**
* 封裝分頁查詢需要的兩個請求傳入的分頁參數(shù)
*/
public class QueryObject {
?? ?private int currentPage = 1; // 當前頁碼，要跳轉到哪一頁的頁碼（需要給默認值）
?? ?private int pageSize = 3; // 每頁顯示條數(shù)（需要給默認值）
}

//DAO接口提供兩個根據(jù)查詢對象的查詢方法
int queryForCount();
List<Product> queryForList(QueryObject qo);
//DAO實現(xiàn)類
@Override
//查詢數(shù)據(jù)庫總數(shù)據(jù)條數(shù)
public int queryForCount() {
?? ?SqlSession session = MyBatisUtil.getSession();
?? ?int totalCount =
?? ?session.selectOne("cn.xxx.mapper.ProductMapper.queryForCount");
?? ?session.close();
?? ?return totalCount;
}
@Override
//查詢某一頁的結果集
public List<Product> queryForList(QueryObject qo) {
?? ?SqlSession session = MyBatisUtil.getSession();
?? ?List<Product> products =
?? ?session.selectList("cn.xxx.mapper.ProductMapper.queryForList",qo);
?? ?session.close();
?? ?return products;
}

<select id="queryForCount" resultType="int">
SELECT COUNT(*) FROM product
</select>
<select id="queryForList" resultType="cn.xxx.domain.Product">
SELECT * FROM product LIMIT #{start}, #{pageSize}
</select>

@Setter
@Getter
/**
* 封裝分頁查詢需要的兩個請求傳入的分頁參數(shù)
*/
public class QueryObject {
?? ?private int currentPage = 1; // 當前頁碼，要跳轉到哪一頁的頁碼（需要給默認值）
?? ?private int pageSize = 3; // 每頁顯示條數(shù)（需要給默認值）
?? ?// 用于 Limit 子句第一個 ? 取值
?? ?public int getStart(){
?? ??? ?return (currentPage - 1) * pageSize;
?? ?}
}

//IProductService接口
public interface IProductService {
?? ?/**
?? ?* 完成查詢某一頁的業(yè)務邏輯功能
?? ?*/
?? ?PageResult<Product> query(QueryObject qo);
}
//Service實現(xiàn)類
public class ProductServiceImpl implements IProductService {
?? ?private IProductDAO productDAO = new ProductDAOImpl();
?? ?@Override
?? ?public PageResult<Product> query(QueryObject qo) {
?? ??? ?// 調用 DAO 查詢數(shù)據(jù)數(shù)量
?? ??? ?int totalCount = productDAO.queryForCount();
?? ??? ?// 為了性能加入判斷，若查詢的數(shù)據(jù)數(shù)量為 0，說明沒有數(shù)據(jù)，返回返回空集合，即集合中沒有
?? ??? ?元素
?? ??? ?if(totalCount == 0){
?? ??? ??? ?return new PageResult(qo.getCurrentPage(), qo.getPageSize(),
?? ??? ??? ?totalCount, Collections.emptyList());
?? ??? ?}
?? ??? ?// 執(zhí)行到這里代表有數(shù)據(jù)，查詢當前頁的結果數(shù)據(jù)
?? ??? ?List<Product> products = productDAO.queryForList(qo);
?? ??? ?return new PageResult(qo.getCurrentPage(), qo.getPageSize(), totalCount,
?? ??? ?products);
?? ?}
}

//創(chuàng)建業(yè)務層對象
private IProductService productService = new ProductServiceImpl();

protected void list(HttpServletRequest req, HttpServletResponse resp) throws
ServletException, IOException {
?? ?QueryObject qo = new QueryObject();
?? ?// 獲取請求參數(shù) currentPage，并轉型封裝
?? ?String currentPage = req.getParameter("currentPage");
?? ?if(StringUtil.hasLength(currentPage)) {
?? ??? ?qo.setCurrentPage(Integer.valueOf(currentPage));
?? ?}
?? ?// 獲取請求參數(shù) pageSize，并轉型封裝
?? ?String pageSize = req.getParameter("pageSize");
?? ?if(StringUtil.hasLength(pageSize)) {
?? ??? ?qo.setPageSize(Integer.valueOf(pageSize));
?? ?}
?? ?// 調用業(yè)務層方法來處理請求查詢某一頁數(shù)據(jù)
?? ?PageResult<Product> pageResult = productService.query(qo);
?? ?// 把數(shù)據(jù)共享給 list.jsp
?? ?req.setAttribute("pageResult", pageResult);
?? ?// 控制跳轉到 list.jsp 頁面
?? ?req.getRequestDispatcher("/WEB-INF/views/product/list.jsp").forward(req,
?? ?resp);
}

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
?? ?<head>
?? ??? ?<title>產(chǎn)品列表</title>
?? ??? ?<script type="text/javascript">
?? ??? ??? ?window.onload = function () {
?? ??? ??? ??? ?var trClzs = document.getElementsByClassName("trClassName");
?? ??? ??? ??? ?for(var i = 0; i < trClzs.length; i++){
?? ??? ??? ??? ??? ?trClzs[i].onmouseover = function () {
?? ??? ??? ??? ??? ??? ?console.log(1);
?? ??? ??? ??? ??? ??? ?this.style.backgroundColor = "gray";
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?trClzs[i].onmouseout = function () {
?? ??? ??? ??? ??? ??? ?console.log(2);
?? ??? ??? ??? ??? ??? ?this.style.backgroundColor = "";
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ?}
?? ??? ??? ?}
?? ??? ??? ?// 分頁 JS
?? ??? ??? ?function changePageSize() {
?? ??? ??? ??? ?document.forms[0].submit();
?? ??? ??? ?}
?? ??? ?</script>
?? ?</head>
?? ?<body>
?? ??? ?<a href="/replaceImg.jsp" rel="external nofollow" ><img src="${USER_IN_SESSION.headImg}" title="更換頭
?? ??? ?像"/></a><br/>
?? ??? ?<a href="/product?cmd=input" rel="external nofollow" >添加</a>
?? ??? ?<form action="/product">
?? ??? ??? ?<table border="1" cellspacing="0" cellpadding="0" width="80%">
?? ??? ??? ??? ?<tr>
?? ??? ??? ??? ??? ?<th>編號</th>
?? ??? ??? ??? ??? ?<th>貨品名</th>
?? ??? ??? ??? ??? ?<th>分類編號</th>
?? ??? ??? ??? ??? ?<th>零售價</th>
?? ??? ??? ??? ??? ?<th>供應商</th>
?? ??? ??? ??? ??? ?<th>品牌</th>
?? ??? ??? ??? ??? ?<th>折扣</th>
?? ??? ??? ??? ??? ?<th>進貨價</th>
?? ??? ??? ??? ??? ?<th>操作</th>
?? ??? ??? ??? ?</tr>
?? ??? ??? ??? ?<c:forEach var="product" items="${pageResult.data}" varStatus="status">
?? ??? ??? ??? ??? ?<tr class="trClassName">
?? ??? ??? ??? ??? ??? ?<td>${status.count}</td>
?? ??? ??? ??? ??? ??? ?<td>${product.productName}</td>
?? ??? ??? ??? ??? ??? ?<td>${product.dir_id}</td>
?? ??? ??? ??? ??? ??? ?<td>${product.salePrice}</td>
?? ??? ??? ??? ??? ??? ?<td>${product.supplier}</td>
?? ??? ??? ??? ??? ??? ?<td>${product.brand}</td>
?? ??? ??? ??? ??? ??? ?<td>${product.cutoff}</td>
?? ??? ??? ??? ??? ??? ?<td>${product.costPrice}</td>
?? ??? ??? ??? ??? ??? ?<td>
?? ??? ??? ??? ??? ??? ??? ?<a href="/product?cmd=delete&id=${product.id}" rel="external nofollow" >刪除</a>
?? ??? ??? ??? ??? ??? ??? ?<a href="/product?cmd=input&id=${product.id}" rel="external nofollow" >修改</a>
?? ??? ??? ??? ??? ??? ?</td>
?? ??? ??? ??? ??? ?</tr>
?? ??? ??? ??? ?</c:forEach>
?? ??? ??? ??? ?<tr align="center">
?? ??? ??? ??? ??? ?<td colspan="9">
?? ??? ??? ??? ??? ??? ?<a href="/product?currentPage=1" rel="external nofollow" >首頁</a>
?? ??? ??? ??? ??? ??? ?<a href="/product?currentPage=${pageResult.prevPage}" rel="external nofollow" >上一頁</a>
?? ??? ??? ??? ??? ??? ?<a href="/product?currentPage=${pageResult.nextPage}" rel="external nofollow" >下一頁</a>
?? ??? ??? ??? ??? ??? ?<a href="/product?currentPage=${pageResult.totalPage}" rel="external nofollow" >尾頁</a>
?? ??? ??? ??? ??? ??? ?當前第 ${pageResult.currentPage} / ${pageResult.totalPage} 頁
?? ??? ??? ??? ??? ??? ?一共 ${pageResult.totalCount} 條數(shù)據(jù)
?? ??? ??? ??? ??? ??? ?跳轉到<input type="number" onchange="changePageSize()"
?? ??? ??? ??? ??? ??? ?name="currentPage" value="${pageResult.currentPage}" style="width: 60px;"頁
?? ??? ??? ??? ??? ??? ?每頁顯示
?? ??? ??? ??? ??? ??? ?<select name="pageSize" onchange="changePageSize()">
?? ??? ??? ??? ??? ??? ??? ?<option value="3" ${pageResult.pageSize == 3 ? 'selected' : ''}> 3 </option>
?? ??? ??? ??? ??? ??? ??? ?<option value="5" ${pageResult.pageSize == 5 ? 'selected' : ''}> 5 </option>
?? ??? ??? ??? ??? ??? ??? ?<option value="8" ${pageResult.pageSize == 8 ? 'selected' : ''}> 8 </option>
?? ??? ??? ??? ??? ??? ?</select>條數(shù)據(jù)
?? ??? ??? ??? ??? ?</td>
?? ??? ??? ??? ?</tr>
?? ??? ??? ?</table>
?? ??? ?</form>
?? ?</body>
</html>