802~805 分页分析，分析具体步骤实现前后台编码

------------恢复内容开始------------

分页分析：

分析具体步骤：

package com.example.web.servlet;
 
import com.example.domain.PageBean;
import com.example.domain.User;
import com.example.service.UserService;
import com.example.service.impl.UserServiceImpl;
 
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Map;
 
@WebServlet("/findUserByPageServlet")
public class FindUserByPageServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        //1.获取参数
        String currentPage = request.getParameter("currentPage");//当前页码
        String rows = request.getParameter("rows");//每页显示条数
        if(currentPage == null || "".equals(currentPage)){
            currentPage = "1";
        }
 
        if(rows == null || "".equals(rows)){
            rows = "5";
        }
        //获取条件查询参数
        Map<String, String[]> condition = request.getParameterMap();
 
 
        //2.调用service查询
        UserService service = new UserServiceImpl();
        PageBean<User> pb = service.findUserByPage(currentPage,rows);
 
        System.out.println(pb);
 
        //3.将PageBean存入request
        request.setAttribute("pb",pb);
        request.setAttribute("condition",condition);//将查询条件存入request
        //4.转发到list.jsp
        request.getRequestDispatcher("/list.jsp").forward(request,response);
    }
 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

PageBean<User> findUserByPage(String currentPage, String rows);
=====
  @Override
    public PageBean<User> findUserByPage(String _currentPage, String _rows) {
        int currentPage = Integer.parseInt(_currentPage);
        int rows = Integer.parseInt(_rows);
 
        if(currentPage <=0){
            currentPage = 1 ;
        }
        //1.创建空的PageBean对象
        PageBean<User> pb = new PageBean<User>();
        //2.设置参数
        pb.setCurrentPage(currentPage);
        pb.setRows(rows);
 
        //3.调用dao查询总记录数
        int totalCount = dao.findTotalCount();
        pb.setTotalCount(totalCount);
        //4.调用dao查询List集合
        //记录开始的记录索引
        int start = (currentPage - 1)* rows;
        List<User> list = dao.findByPage(start,rows);
        pb.setList(list);
 
        //计算总页码
        int totalPage = (totalCount % rows)  == 0? totalCount/rows : (totalCount/rows)+1;
        pb.setTotalPage(totalPage);
 
        return pb;
    }
=====
    List<User> findByPage(int start, int rows);//分页查询每页记录
=====
 @Override
    public int findTotalCount() {
        String sql = "select count(*) from user";
        return template.queryForObject(sql,Integer.class);
    }
 
    @Override
    public List<User> findByPage(int start, int rows) {
        String sql = "select *from user limit ? , ?";
 
        return template.query(sql,new BeanPropertyRowMapper<User>(User.class),start,rows);
    }

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<%@ page contentType="text/html;charset=UTF-8" language="java" %>
 
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
 
<!DOCTYPE html>
<!-- 网页使用的语言 -->
<html lang="zh-CN">
<head>
    <!-- 指定字符集 -->
    <meta charset="utf-8">
    <!-- 使用Edge最新的浏览器的渲染方式 -->
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <!-- viewport视口：网页可以根据设置的宽度自动进行适配，在浏览器的内部虚拟一个容器，容器的宽度与设备的宽度相同。
    width: 默认宽度与设备的宽度相同
    initial-scale: 初始的缩放比，为1:1 -->
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- 上述3个meta标签*必须*放在最前面，任何其他内容都*必须*跟随其后！ -->
    <title>用户信息管理系统</title>
 
    <!-- 1. 导入CSS的全局样式 -->
    <link href="css/bootstrap.min.css" rel="stylesheet">
    <!-- 2. jQuery导入，建议使用1.9以上的版本 -->
    <script src="js/jquery-2.1.0.min.js"></script>
    <!-- 3. 导入bootstrap的js文件 -->
    <script src="js/bootstrap.min.js"></script>
    <style type="text/css">
        td, th {
            text-align: center;
        }
    </style>
    <script>
        function deleteUser(id){
            //用户安全提示
            if(confirm("确定删除嘛？")){
                location.href="${pageContext.request.contextPath}/delUserServlet?id="+id;
            }
        }
 
        window.onload = function () {
            document.getElementById("delSelected").onclick = function () {
                if (confirm("数据一但删除无法恢复")){
                    //提交表单
                    document.getElementById("form").submit();
                }
                }
 
            //1.获取第一个cb
            document.getElementById("firstCb").onclick = function(){
                //2.获取下边列表中所有的cb
                var cbs = document.getElementsByName("uid");
                //3.遍历
                for (var i = 0; i < cbs.length; i++) {
                    //4.设置这些cbs[i]的checked状态 = firstCb.checked
                    cbs[i].checked = this.checked;
                }
            }
        }
 
    </script>
</head>
<body>
<div class="container">
    <h3 style="text-align: center">用户信息列表</h3>
 
    <div style="float: left">
        <form class="form-inline">
            <div class="form-group">
                <label for="exampleInputName2">姓名</label>
                <input type="text" class="form-control" id="exampleInputName2">
            </div>
            <div class="form-group">
                <label for="exampleInputName3">籍贯</label>
                <input type="text" class="form-control" id="exampleInputName3">
            </div>
            <div class="form-group">
                <label for="exampleInputEmail2">邮箱</label>
                <input type="email" class="form-control" id="exampleInputEmail2">
            </div>
            <button type="submit" class="btn btn-default">查询</button>
        </form>
    </div>
    <div style="float: right; margin: 5px ">
        <a class="btn btn-primary" href="${pageContext.request.contextPath}/add.jsp">添加联系人</a>
        <a class="btn btn-primary" href="javascript:void(0);" id="delSelected">删除选中</a>
    </div>
    <form id="form" action="${pageContext.request.contextPath}/delSelectedServlet" method="post">
    <table border="1" class="table table-bordered table-hover">
        <tr class="success">
            <th><input type="checkbox" id="firstCb"></th>
            <th>编号</th>
            <th>姓名</th>
            <th>性别</th>
            <th>年龄</th>
            <th>籍贯</th>
            <th>QQ</th>
            <th>邮箱</th>
            <th>操作</th>
        </tr>
 
        <c:forEach items="${pb.list}" var="user" varStatus="s">
            <tr>
                <td><input type="checkbox" name="uid" value="${user.id}"></td>
                <td>${s.count}</td>
                <td>${user.name}</td>
                <td>${user.gender}</td>
                <td>${user.age}</td>
                <td>${user.address}</td>
                <td>${user.qq}</td>
                <td>${user.email}</td>
                <td><a class="btn btn-default btn-sm" href="${pageContext.request.contextPath}/findUserServlet?id=${user.id}">修改</a> 
                    <a class="btn btn-default btn-sm" href="javascript:deleteUser(${user.id})">删除</a></td>
            </tr>
 
        </c:forEach>
    </table>
    </form>
    <div>
        <nav aria-label="Page navigation">
            <ul class="pagination">
                <c:if test="${pb.currentPage==1}">
                    <li class="disabled">
                </c:if>
 
                <c:if test="${pb.currentPage !=1}">
                    <li>
                </c:if>
 
 
                    <a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${pb.currentPage - 1}&rows=5" aria-label="Previous">
                        <span aria-hidden="true">«</span>
                    </a>
                </li>
 
               <c:forEach begin="1" end="${pb.totalPage}" var="i">
 
                   <c:if test="${pb.currentPage == i}">
                       <li class="active"><a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${i}&rows=5">${i}</a></li>
                   </c:if>
                   <c:if test="${pb.currentPage != i}">
                       <li><a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${i}&rows=5">${i}</a></li>
                   </c:if>
 
               </c:forEach>
                <li>
                    <a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${pb.currentPage + 1}&rows=5" aria-label="Next">
                        <span aria-hidden="true">»</span>
                    </a>
                </li>
                <span style="font-size: 25px;margin-left: 5px">
                    共${pb.totalCount}条记录共${pb.totalPage}页
                </span>
            </ul>
        </nav>
    </div>
</div>
</body>
</html>

package com.example.domain;
 
import java.util.List;
 
/**
 * 分页对象
 */
public class PageBean<T>{
    private int totalCount; // 总记录数
    private int totalPage ; // 总页码
    private List<T> list ; // 每页的数据
    private int currentPage ; //当前页码
    private int rows;//每页显示的记录数
 
    @Override
    public String toString() {
        return "PageBean{" +
                "totalCount=" + totalCount +
                ", totalPage=" + totalPage +
                ", list=" + list +
                ", currentPage=" + currentPage +
                ", rows=" + rows +
                '}';
    }
 
    public int getTotalCount() {
        return totalCount;
    }
 
    public void setTotalCount(int totalCount) {
        this.totalCount = totalCount;
    }
 
    public int getTotalPage() {
        return totalPage;
    }
 
    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }
 
    public List<T> getList() {
        return list;
    }
 
    public void setList(List<T> list) {
        this.list = list;
    }
 
    public int getCurrentPage() {
        return currentPage;
    }
 
    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }
 
    public int getRows() {
        return rows;
    }
 
    public void setRows(int rows) {
        this.rows = rows;
    }
}