Servlet + JSP 数据分页的实现

 

  本篇数据分页的实现，采用Oracle 数据库，获取SCOTT 用户 EMP 表中的数据，分页将其显示出来。

1.首先创建一个对象 UserData，用以保存从数据库中获取的数据。

package com.tool;

import java.math.BigDecimal;
import java.util.Date;

/**
 * Created by lx_sunwei on 14-1-6.
 */
public class UserData {

    /**
     * EMP表中的数据属性
     */
    private String ename;
    private String job;
    private BigDecimal empno;
    private BigDecimal mgr;
    private Date hireDate;
    private BigDecimal sal;
    private BigDecimal comm;
    private BigDecimal deptno;

    public BigDecimal getEmpno() {
        return empno;
    }

    public void setEmpno(BigDecimal empno) {
        this.empno = empno;
    }

    public BigDecimal getMgr() {
        return mgr;
    }

    public void setMgr(BigDecimal mgr) {
        this.mgr = mgr;
    }

    public Date getHireDate() {
        return hireDate;
    }

    public void setHireDate(Date hireDate) {
        this.hireDate = hireDate;
    }

    public BigDecimal getSal() {
        return sal;
    }

    public void setSal(BigDecimal sal) {
        this.sal = sal;
    }

    public BigDecimal getComm() {
        return comm;
    }

    public void setComm(BigDecimal comm) {
        this.comm = comm;
    }

    public BigDecimal getDeptno() {
        return deptno;
    }

    public void setDeptno(BigDecimal deptno) {
        this.deptno = deptno;
    }

    public String getEname() {
        return ename;
    }

    public void setEname(String ename) {
        this.ename = ename;
    }

    public String getJob() {
        return job;
    }

    public void setJob(String job) {
        this.job = job;
    }
}

2.创建一个 DBHelper 对象用以与数据库进行交互

package com.dao;

import com.tool.UserData;

import java.math.BigDecimal;
import java.sql.*;
import java.util.*;
import java.util.Date;

/**
 * Created by lx_sunwei on 14-1-6.
 */
public class DBHelper {

    Connection conn;  //数据库连接对象
    PreparedStatement pt;  //SQL语句预处理对象
    ResultSet rs;  //结果集对象

    public  DBHelper(){
        try {
            Class.forName("oracle.jdbc.driver.OracleDriver");  //装载驱动
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    /**
     * 获取当前页的数据
     * @param curPage
     * @param rowsPerPage
     * @return
     */
    public List<UserData> getData(int curPage, int rowsPerPage) {

        List<UserData> dataList = new ArrayList<>();
        String url = "jdbc:oracle:thin:@localhost:1521:orcl";
        try {
            conn = DriverManager.getConnection(url,"scott","tiger");
            String sql = "select * from emp where rownum <= ((? - 1) * "+rowsPerPage+" + "+rowsPerPage+") minus " +
                    " select * from emp where rownum <= (? - 1) * "+rowsPerPage+" ";
            pt = conn.prepareStatement(sql);
            pt.setInt(1,curPage);
            pt.setInt(2,curPage);
            rs = pt.executeQuery();
            while (rs.next()){
                /**
                 * 从结果集中取得数据
                 */
                UserData userData = new UserData();
                BigDecimal empno = rs.getBigDecimal("empno");
                String ename = rs.getString("ename");
                String job = rs.getString("job");
                BigDecimal mgr = rs.getBigDecimal("mgr");
                Date hireDate = rs.getDate("hiredate");
                BigDecimal sal = rs.getBigDecimal("sal");
                BigDecimal comm = rs.getBigDecimal("comm");
                BigDecimal deptno = rs.getBigDecimal("deptno");
                /**
                 * 设置对象属性
                 */
                userData.setEmpno(empno);
                userData.setEname(ename);
                userData.setJob(job);
                userData.setMgr(mgr);
                userData.setHireDate(hireDate);
                userData.setSal(sal);
                userData.setComm(comm);
                userData.setDeptno(deptno);
                dataList.add(userData);  //把对象添加集合中
            }
            rs.close();
            pt.close();
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return dataList;
    }

    /**
     * 返回总页数
     * @return
     */
    public int getMaxPage(int rowsPerPage) {
        int maxPage;
        int maxRowCount = 0;
        String url = "jdbc:oracle:thin:@localhost:1521:orcl";
        try {
            conn = DriverManager.getConnection(url,"scott","tiger");  //创建数据库连接
            String sql = "select count(*) from emp";
            pt = conn.prepareStatement(sql);
            rs = pt.executeQuery();
            if (rs.next()){
                maxRowCount = rs.getInt(1);  //总行数
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        maxPage = (maxRowCount + rowsPerPage - 1) / rowsPerPage;  //总页数
        return maxPage;
    }
}

3.创建 Servlet 对显示页面进行控制

package com.servlet;

import com.dao.DBHelper;
import com.tool.UserData;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.*;

/**
 * Created by lx_sunwei on 14-1-6.
 */
public class Servlet extends HttpServlet {

    public int rowsPerPage;  //每页显示的行数
    public int curPage;  //当前页页码
    public int maxPage;  //总共页数
    DBHelper db = new DBHelper();
    public Servlet(){
        rowsPerPage = 5;
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String curPage1 = request.getParameter("page");  //获取当前页页码
        if (curPage1 == null){
            curPage = 1;
            request.setAttribute("curPage",curPage);  //设置curPage对象
        }else {
            curPage = Integer.parseInt(curPage1);
            if (curPage < 1){
                curPage = 1;
            }
            request.setAttribute("curPage",curPage);
        }

        List<UserData> dataList;
        dataList = db.getData(curPage,rowsPerPage);  //获取当前页的数据
        maxPage = db.getMaxPage(rowsPerPage);  //获取总页数
        request.setAttribute("dataList",dataList);
        request.setAttribute("maxPage", maxPage);

        RequestDispatcher rd = request.getRequestDispatcher("pagemain.jsp");  //将请求转发到pagemain.jsp页面
        rd.forward(request,response);
    }

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

4.创建 JSP 页面，显示数据。

<%@ page import="java.util.List" %>
<%@ page import="com.tool.UserData" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>servlet数据分页</title>
    <link rel="stylesheet" type="text/css" href="css.css">
</head>
<body>
<div style="margin-top: 15%; margin-left: 25%">
    <table>
        <caption>SCOTT用户，EMP表中的数据</caption>
        <%! int curPage,maxPage; %>
        <% curPage =Integer.parseInt(request.getAttribute("curPage").toString()); %> <!--取得当前页-->
        <% maxPage =Integer.parseInt((String)request.getAttribute("maxPage").toString()); %> <!--取得总页数-->
        <%if (request.getAttribute("dataList") == null){
        %>
        <tr>
            <td colspan="8">没有数据</td>
        </tr>
        <%
        }else {
        %>
        <tr>
            <!--表头-->
            <th>EMPNO</th>
            <th>ENAME</th>
            <th>JOB</th>
            <th>MGR</th>
            <th>HIREDATE</th>
            <th>SAL</th>
            <th>COMM</th>
            <th>DEPTNO</th>
        </tr>
        <%
            List list = (List) request.getAttribute("dataList");
            for (Object aList : list) {
                UserData userData = (UserData) aList;
        %>
        <tr>
            <!--取得表中数据-->
            <td><%= userData.getEmpno() %></td>
            <td><%= userData.getEname() %></td>
            <td><%= userData.getJob() %></td>
            <td><%= userData.getMgr() %></td>
            <td><%= userData.getHireDate() %></td>
            <td><%= userData.getSal() %></td>
            <td><%= userData.getComm() %></td>
            <td><%= userData.getDeptno() %></td>
        </tr>
        <%
                }
            }
        %>
    </table>
</div>
<div style="margin-top: 8%; margin-left: 29%">
    第<%= curPage %>页，共<%= maxPage %>页&nbsp;&nbsp;
    <%if (curPage > 1){
    %>
    <a href="Servlet?page=1">首页</a>
    <a href="Servlet?page=<%=curPage - 1%>">上一页</a>
    <%
    }else {
    %>
    首页 上一页
    <%
        }%>
    <%if (curPage < maxPage){
    %>&nbsp;&nbsp;
    <a href="Servlet?page=<%=curPage + 1%>">下一页</a>
    <a href="Servlet?page=<%=maxPage %>">尾页</a>
    <%
    }else {
    %>
    下一页 尾页
    <%
        }%>
    &nbsp;&nbsp;转至第&nbsp;<form name="form1" action="Servlet" method="get">
    <label>
        <select name="page" onchange="document.form1.submit()">
            <%for ( int i = 1; i <= maxPage; i++){
                if (i == curPage){
            %>
            <!--当前页页码默认选中-->
            <option selected value="<%= i%>"><%= i %></option>
            <%
            }else {
            %>
            <option value="<%= i %>"><%= i %></option>
            <%
                    }
                }%>
        </select>
    </label>
</form>&nbsp;页
</div>
</body>
</html>

web.xml 中的配置文件为：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
          http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
           version="3.0">

    <servlet>
        <servlet-name>Servlet</servlet-name>
        <servlet-class>com.servlet.Servlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Servlet</servlet-name>
        <url-pattern>/Servlet</url-pattern>
    </servlet-mapping>

</web-app>

把项目部署到 Tomcat 服务器上，输入地址：http://localhost:8080/Servlet   显示如下页面