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基于JSP的分页技术基础

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  • Post category:其他

分页技术在web开发中必不可少，一些成熟的框架已经将分页技术封装好，直接用就可以了。这里写一下分页技术的基础，JSP+Servlet+c3p0+mysql。

数据库
这里写图片描述
建立如图所示的表t_emp,有三个字段：empId,empName,deptId。

项目构建
这里写图片描述

项目采用c3p0连接池和DButils工具，前台使用JSP，业务逻辑控制使用Servlet。

工具类
代码：

package utils;

import javax.sql.DataSource;

import org.apache.commons.dbutils.QueryRunner;

import com.mchange.v2.c3p0.ComboPooledDataSource;

/**
 * JDBCUtils工具类
 * @author 90948
 */
public class JdbcUtil {
    /**
     * 初始化c3p0连接池
     */
    private static DataSource dataSource = null;
    static {
        dataSource = new ComboPooledDataSource();
    }

    /**
     * 创建DbUtils核心类
     * 如果在创建QueryRunner对象时传入了数据源，那么在使用QueryRunner对象方法时候就不需要
     * 使用连接对象，也不用显示关闭数据库连接对象，由连接池管理。
     */
    public static QueryRunner getQueryRuuner() {
        return new QueryRunner(dataSource);
    }
}

这里使用了c3p0连接池和DBUtil组件，c3p0连接池的配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
	<default-config>
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="jdbcUrl">jdbc:mysql://localhost:3306/db_page</property>
		<property name="user">root</property>
		<property name="password">root</property>
		<property name="initialPoolSize">5</property>
		<property name="maxPoolSize">5</property>
		<property name="minPoolSize">1</property>
		<property name="acquireIncrement">2</property>
	</default-config>
</c3p0-config>

分页Bean

package pojo;

import java.util.List;

/**
 * 分页实体
 * @author 90948
 */
public class PageBean<T> {
    private int currentPage = 1; //当前页

    private int pageCount = 4; //每页显示的行数

    private int totalCount;//总记录数

    private int totalPage; //总页数=总记录数/每页显示的行数，有余数则+1

    private List<T> pageData;

    public int getCurrentPage() {
        return currentPage;
    }

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

    public int getPageCount() {
        return pageCount;
    }

    public void setPageCount(int pageCount) {
        this.pageCount = pageCount;
    }

    public int getTotalCount() {
        return totalCount;
    }

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

    public int getTotalPage() {
        if (totalCount % pageCount == 0) {
            totalPage = totalCount / pageCount;
        } else {
            totalPage = totalCount / pageCount + 1;
        }
        return totalPage;
    }

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

    public List<T> getPageData() {
        return pageData;
    }

    public void setPageData(List<T> pageData) {
        this.pageData = pageData;
    }

}

这里需要注意的是总页数的计算方法：总页数=总记录数/每页显示的行数，有余数则+1

Employee Bean

package pojo;

public class Employee {
    private int empId;

    private String empName;

    private int deptId;

    public int getEmpId() {
        return empId;
    }

    public void setEmpId(int empId) {
        this.empId = empId;
    }

    public String getEmpName() {
        return empName;
    }

    public void setEmpName(String empName) {
        this.empName = empName;
    }

    public int getDeptId() {
        return deptId;
    }

    public void setDeptId(int deptId) {
        this.deptId = deptId;
    }

}

普通的员工Bean，没有特殊的地方。

Dao层
接口：

package dao;

import java.sql.SQLException;

import pojo.Employee;
import pojo.PageBean;

public interface IEmployeeDao {
    /**
     * 分页查询数据
     * @param pb
     */
    void getAll(PageBean<Employee> pb) throws SQLException;

    /**
     * 获取总记录数
     */
    int getTotalCount() throws SQLException;
}

实现类：

package dao.impl;

import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import pojo.Employee;
import pojo.PageBean;
import utils.JdbcUtil;
import dao.IEmployeeDao;

public class EmployeeDaoImpl implements IEmployeeDao {

    @Override
    public void getAll(PageBean<Employee> pb) throws SQLException {
        //获取当前页，计算查询的起始行和返回的行数
        int currentPage = pb.getCurrentPage();

        int start = (currentPage - 1) * pb.getPageCount();
        int count = pb.getPageCount();

        //查询总记录数
        int totalCount = this.getTotalCount();
        pb.setTotalCount(totalCount);

        //分页查询数据，将数据存储到pb当中
        String sql = "select * from t_emp limit ?,?";
        QueryRunner qr = JdbcUtil.getQueryRuuner();
        List<Employee> pageData = qr.query(sql, new BeanListHandler<Employee>(
                Employee.class), start, count);
        pb.setPageData(pageData);
    }

    @Override
    public int getTotalCount() throws SQLException {
        String sql = "select count(*) from t_emp";
        QueryRunner qr = JdbcUtil.getQueryRuuner();
        Long count = qr.query(sql, new ScalarHandler<Long>());
        return count.intValue();
    }
}

Service层
接口：

package service;

import java.sql.SQLException;

import pojo.Employee;
import pojo.PageBean;

public interface IEmployeeService {
    /**
     * 分页查询数据
     * @param pb
     */
    void getAll(PageBean<Employee> pb) throws SQLException;
}

实现类：

package service.impl;

import java.sql.SQLException;

import pojo.Employee;
import pojo.PageBean;
import service.IEmployeeService;
import dao.IEmployeeDao;
import dao.impl.EmployeeDaoImpl;

public class EmployeeServiceImpl implements IEmployeeService {
    private IEmployeeDao dao = new EmployeeDaoImpl();

    @Override
    public void getAll(PageBean<Employee> pb) throws SQLException {
        dao.getAll(pb);
    }

}

Servlet

package servlet;

import java.io.IOException;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import pojo.Employee;
import pojo.PageBean;
import service.IEmployeeService;
import service.impl.EmployeeServiceImpl;

public class IndexServlet extends HttpServlet {

    private IEmployeeService service = new EmployeeServiceImpl();

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取当前页，第一次访问当前也参数为空
        String currentPage = request.getParameter("currentPage");
        if (currentPage == null || "".equals(currentPage.trim())) {
            currentPage = "1";//第一次访问，当前页为1
        }
        int currPage = Integer.parseInt(currentPage);
        //创建PageBean对象
        PageBean<Employee> pageBean = new PageBean<Employee>();
        pageBean.setCurrentPage(currPage);
        //调用Service方法
        try {
            service.getAll(pageBean);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        //将PageBean设置到request域中
        request.setAttribute("pageBean", pageBean);
        //跳转
        request.getRequestDispatcher("/WEB-INF/list.jsp").forward(request,
            response);
    }

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

}

JSP

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>分页查询</title>
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
  </head>
  
  <body>
    <table border="1" align="center" cellpadding="5" cellspacing="0" width="80%">
    	<tr>
    		<th align="center">序号</th>
    		<th align="center">员工编号</th>
    		<th align="center">员工姓名</th>
    	</tr>
 		<c:choose>
 			<c:when test="${not empty requestScope.pageBean.pageData }">
 				<c:forEach var="emp" items="${requestScope.pageBean.pageData }" varStatus="vs">
 					<tr>
 						<td align="center">${vs.count }</td>
 						<td align="center">${emp.empId }</td>
 						<td align="center">${emp.empName }</td>
 					</tr>
 				</c:forEach>
 			</c:when>
 			<c:otherwise>
 				<tr>
 					<td colspan="3">对不起，查询的数据不存在</td>
 				</tr>
 			</c:otherwise>
 		</c:choose>
 		<tr>
 			<td colspan="3" align="center">
 			<span>当前${requestScope.pageBean.currentPage }/${requestScope.pageBean.totalPage }页</span>&nbsp;&nbsp;&nbsp;&nbsp;
 			<c:if test="${requestScope.pageBean.currentPage != 1 }">
	 			<a href="${pageContext.request.contextPath%20}/IndexServlet?currentPage=1">首页</a>　
	 			<a href="${pageContext.request.contextPath%20}/IndexServlet?currentPage=${requestScope.pageBean.currentPage-1}">上一页</a>
	 		</c:if>
	 		<c:if test="${requestScope.pageBean.currentPage != requestScope.pageBean.totalPage }">
	 			<a href="${pageContext.request.contextPath%20}/IndexServlet?currentPage=${requestScope.pageBean.currentPage+1}">下一页</a>　
	 			<a href="${pageContext.request.contextPath%20}/IndexServlet?currentPage=${requestScope.pageBean.totalPage}">末页</a>
	 		</c:if>　
 			</td>
 		</tr>
    </table>
  </body>
</html>

页面展示1：
这里写图片描述

页面展示2：
这里写图片描述

页面展示3：
这里写图片描述

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