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Servlet分页查询

来源：步遥情感网

分页查询：

PageBean的主要属性：

totalCount 页面展示的数据的总条数，通过数据库查询

totalPage 数据分页的总页数，计算获得（ Math.ceil向上取整（总条数/（每页显示的条数*1.0））

rows 每页显示的行数，自定义

currentPage 当前页码，由前端获取

List<Student> list 显示数据的内容，数据库获取

Student的主要属性：

id 学生id

name 学生姓名

age学生年龄

代码：

Servlet:用于获取数据

package com.xmcc.servlet;

import com.xmcc.entiy.Page;
import com.xmcc.entiy.Student;
import com.xmcc.service.StudentService;
import com.xmcc.service.lmpl.StudentServicelmpl;

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.*;

@WebServlet(name = "Servlet" ,value = "/Servlet")
public class Servlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        StudentService studentService = new StudentServicelmpl();
        response.setContentType("text/html;charset=utf-8");
        String currentPage = request.getParameter("currentPage");
        String curremtPagelast = request.getParameter("curremtPagelast");
        String curremtPagenext = request.getParameter("curremtPagenext");
//控制上下页
        if(curremtPagelast != null)//控制上一页
        {
            int curremtPagelast1 = Integer.parseInt(curremtPagelast);
            System.out.println(curremtPagelast1);
            currentPage = String.valueOf(curremtPagelast1-1);
            System.out.println("这是上一页="+currentPage);
        }
        if(curremtPagenext !=null)//控制下一页
        {
            int curremtPagenext1 = Integer.parseInt(curremtPagenext);
            System.out.println(curremtPagenext1);
            currentPage = String.valueOf(curremtPagenext1+1);
            System.out.println("这是下一页="+currentPage);
        }
        if(currentPage == null){//如果当前页数是空，设置页数为1
            currentPage = "1";
        }
//将studentService里面的getStudentsByPage方法的结果返回到Page中，“3”为每页保存的数据数
        Page page = studentService.getStudentsByPage(3, Integer.parseInt(currentPage));
        request.getSession().setAttribute("pb", page);//将数据保存到Seesion中
        request.getSession().setAttribute("page", currentPage);
        response.sendRedirect("/index.jsp");
    }

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

StudentService：

package com.xmcc.service;

import com.xmcc.entiy.Admin;
import com.xmcc.entiy.Page;
import com.xmcc.entiy.Student;

import java.util.ArrayList;
import java.util.List;

public interface StudentService {
    List<Student> getStudent() ;
    Page getStudentsByPage(int rows, int currentPage);
}

StudentServicelmpl：StudentService的实现

import com.xmcc.dao.StudentDao;
import com.xmcc.dao.impl.StudentDaolmpl;
import com.xmcc.entiy.Admin;
import com.xmcc.entiy.Page;
import com.xmcc.entiy.Student;
import com.xmcc.service.StudentService;

import java.util.ArrayList;
import java.util.List;

public class StudentServicelmpl implements StudentService {
    StudentDao studentDao = new StudentDaolmpl() ;
    @Override
//查询所有的学生
    public List<Student> getStudent() {
        return studentDao.getStudent();
    }

    @Override
    public Page getStudentsByPage(int rows, int currentPage) {
//将第X页页面的数据展示出来
        List<Student> students = studentDao.getStudentsByPage(rows,currentPage );
//获取所有的数据条数
        int totalCount =  studentDao.getTotalCount();
        System.out.println(totalCount);
        Page page = new Page(totalCount,rows,currentPage,students);
        return page;
    }

  
}

StudentDao：

package com.xmcc.dao;

import com.xmcc.entiy.Admin;
import com.xmcc.entiy.Student;

import java.util.ArrayList;
import java.util.List;

public interface StudentDao {
    List<Student> getStudent();
    List<Student> getStudentsByPage(int rows, int currentPage);
    int getTotalCount();
}

StudentDaoimpl:

package com.xmcc.dao.impl;

import com.xmcc.dao.StudentDao;
import com.xmcc.entiy.Admin;
import com.xmcc.entiy.Student;
import com.xmcc.utils.JDBCutils;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class StudentDaolmpl implements StudentDao {
    @Override
    public List<Student> getStudent()  {
        ArrayList<Student> students = new ArrayList<>();
//设置连接对象
        Connection conn = null;
        try {
//获取连接，连接数据库
            conn = JDBCutils.getConnction();
//数据库执行语句
            String sql = "select * from std";
//获取执行对象
            PreparedStatement ps = conn.prepareStatement(sql);
//执行数据库语句，并将执行结果保存到resultSet中
            ResultSet resultSet = ps.executeQuery();
//遍历resultSet
            while (resultSet.next())
            {
                int id = resultSet.getInt(1);//resultSet.getInt()中可以直接写字段名，例如:resultSet.getInt(“id”)
                String name = resultSet.getString(2);
                int age = resultSet.getInt(3);
                students.add(new Student(id,name,age));
            }
            JDBCutils.close(ps,conn ,resultSet );
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return students;
    }

    @Override
    public List<Student> getStudentsByPage(int rows, int currentPage) {
        ArrayList<Student> students = new ArrayList<>();
        Connection conn = null;
        try {
            conn = JDBCutils.getConnction();
            String sql = "select * from std limit ?,?";
            PreparedStatement ps = conn.prepareStatement(sql);
//设置第一个？处的值为(currentPage-1)*rows，这里主要是获取当前页是从数据库中第几条数据开始展示
            ps.setInt(1,(currentPage-1)*rows );
//设置第二个？处的值为rows,这里主要是获取需要展示多少条数据
            ps.setInt(2,rows );
            ResultSet resultSet = ps.executeQuery();
            while (resultSet.next())
            {
                int id = resultSet.getInt(1);
                String name = resultSet.getString(2);
                int age = resultSet.getInt(3);
                students.add(new Student(id,name,age));
            }
            JDBCutils.close(ps,conn ,resultSet );
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return students;
    }

    @Override
    public int getTotalCount() {
        Connection conn = null;
        int row = 0;
        try { 
            conn = JDBCutils.getConnction();
            String sql = "select * from std";
            PreparedStatement ps = conn.prepareStatement(sql);
            ResultSet resultSet = ps.executeQuery();
//获得resultSet的最后一行
            resultSet.last();
//获得当前resultSet的“下标”
            row = resultSet.getRow();
            JDBCutils.close(ps, conn, resultSet);
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return row;
    }


}

数据库工具类：

package com.xmcc.utils;

import com.alibaba.druid.pool.DruidDataSource;
import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCutils {
//初始化数据源
    private static DataSource dataSource;
    static {
//读取流获取druid.properties
//JDBCUtilsConfig.class是获得当前对象所属的class对象 
//getClassLoader()是取得该Class对象的类装载器 
//getResourceAsStream(“database.properties”) 调用类加载器的方法加载 资源，返回的是字节流
//使用Properties类是为了可以从.properties属性文件对应的文件输入流中，加载属性列表到Properties类对象，然后通过getProperty方法用指定的键在此属性列表中搜索属性 
        InputStream in = JDBCutils.class.getClassLoader().getResourceAsStream("druid.properties");

        Properties properties = new Properties();
        try {
            properties.load(in);
//创建连接池对象
            dataSource = DruidDataSourceFactory.createDataSource(properties);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
//关闭连接
    public static Connection getConnction() throws SQLException {
        return dataSource.getConnection();
    }
    public static DataSource getDataSource() {
        return dataSource;
    }
    public static void close(Statement statement, Connection conn) throws SQLException {
        statement.close();
        conn.close();
    }
    public static void close(Statement statement, Connection conn, ResultSet resultSet) throws SQLException {
        if(statement != null){
            statement.close();
        }
        if(conn != null){
            conn.close();
        }
        if(resultSet != null){
            resultSet.close();
        }
    }
}

Page实体类：

package com.xmcc.entiy;

import java.util.List;

public class Page {
    private int totalCount;//总条数  ---------数据库
    private int totalPage;//总页数    ----------算出来的
    private int rows;//每页显示行数 --------------自定义
    private int currentPage;//当前页码    ---------前端
    private List<Student> list; // 内容---------数据库

    public Page() {
    }

    public int getTotalCount() {
        return totalCount;
    }

    public void setTotalCount(int totalCount) {
        this.totalCount = totalCount;
    }

    public int getTotalPage() {
//计算有多少页，采用向上取整
        int page = (int) Math.ceil(totalCount/(rows*1.0));
        System.out.println("page="+page);
        return page;
    }

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

    public int getRows() {
        return rows;
    }

    public void setRows(int rows) {
        this.rows = rows;
    }

    public int getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }

    public List<Student> getList() {
        return list;
    }

    public void setList(List<Student> list) {
        this.list = list;
    }

    public Page(int totalCount,  int rows, int currentPage, List<Student> list) {
        this.totalCount = totalCount;
        this.rows = rows;
        this.currentPage = currentPage;
        this.list = list;
    }
}

页面展示：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<html>
<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>用户信息管理系统</title>
  <link href="css/bootstrap.min.css" rel="stylesheet">
  <script src="js/jquery-2.1.0.min.js"></script>
  <script src="js/bootstrap.min.js"></script>
  <style type="text/css">
    td, th {
      text-align: center;
    }
  </style>
</head>
<body>
<div class="container">
  <h3 style="text-align: center">用户信息列表</h3>
  <table border="1" class="table table-bordered table-hover">

    <tr class="success">
      <th>编号</th>
      <th>姓名</th>
      <th>年龄</th>

      <th>操作</th>
    </tr>
//使用c:forEach遍历session中名为“pb”的session中list属性的值
    <c:forEach items="${pb.list}" var="stu">
      <tr>
        <td>${stu.id}</td>
        <td>${stu.name}</td>
        <td>${stu.age}</td>

        <td><a class="btn btn-default btn-sm" href="/selectStudentByIdServlet?id=${stu.id}">修改</a>&nbsp;<a class="btn btn-default btn-sm" href="/deleteServlet?id=${stu.id}">删除</a></td>
      </tr>
    </c:forEach>
    <tr>
      <td colspan="8" align="center"><a class="btn btn-primary" href="add.html">添加联系人</a></td>
    </tr>
  </table>
  <div>
    <nav aria-label="Page navigation">
      <ul class="pagination">
        <li id="curremtPagelast">
          <a class="curremtPagelast" href="/Servlet?curremtPagelast=${page}" aria-label="Previous">
            <span aria-hidden="true">&laquo;</span>
          </a>
        </li>
        <c:forEach begin="1" end="${pb.totalPage}" var="i" step="1">
          <li id="i${i}" class="page"><a  class="page1" href="/Servlet?currentPage=${i}">${i}</a></li>
        </c:forEach>
        <li id="curremtPagenext">
          <a class="curremtPagenext" href="/Servlet?curremtPagenext=${page}" aria-label="Next">
            <span aria-hidden="true">&raquo;</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>
<script>
    $("#i${page}").addClass('active');
    var page=${page};
    console.log(page);
    if(page===1){
        console.log("last1")
        $(".curremtPagelast").attr("disabled",true);
        $(".curremtPagelast").css("pointer-events","none");
        $("#curremtPagelast").addClass('disabled')
    }else {
        console.log("last2")
        $(".curremtPagelast").attr("disabled",false);
        $(".curremtPagelast").css("pointer-events","auto");
        $("#curremtPagelast").removeClass('disabled')
    }
    var totalPage=${pb.totalPage}
    if(page===totalPage){
        console.log("next1")
        $(".curremtPagenext").attr("disabled",true);
        $(".curremtPagenext").css("pointer-events","none");
        $("#curremtPagenext").addClass('disabled')
    }else {
        console.log("next2")
        $(".curremtPagenext").attr("disabled",false);
        $(".curremtPagenext").css("pointer-events","auto");
        $("#curremtPagenext").removeClass('disabled')
    }
</script>
</body>
</html>

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