实现一个简单的分页

此分页为利用java实现的简单的分页，利用jstl和c3p0、dbutils工具、利用maven管理jar包

使用的是数据库为mysql表为students

声明此为简单的展示分页而已，且代码实现不全面，只是展示简单的实现原理，可以在此demo上进行修改扩展

下图为此demo的目录结构

maven的pom.xml部分代码如下

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>com.mchange</groupId>
      <artifactId>c3p0</artifactId>
      <version>0.9.5.2</version>
    </dependency>
    <dependency>
      <groupId>commons-dbutils</groupId>
      <artifactId>commons-dbutils</artifactId>
      <version>1.6</version>
    </dependency>
    <dependency>
      <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
      <version>2.4</version>
    </dependency>
    <dependency>
      <groupId>commons-logging</groupId>
      <artifactId>commons-logging</artifactId>
      <version>1.2</version>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.38</version>
    </dependency>
  </dependencies>

一个简单的数据库

demo的目录结构

entity目录下的javabean代码如下

package com.ccx.entity;

import java.io.Serializable;

public class Student implements Serializable {
    private Integer id;
    private String name;
    private Double sal;

    public Student() {
    }

    public Student(Integer id, String name, Double sal) {
        this.id = id;
        this.name = name;
        this.sal = sal;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Double getSal() {
        return sal;
    }

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

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", sal=" + sal +
                '}';
    }
}

utils工具类JdbcUtils类

package com.ccx.utils;


import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.apache.commons.dbutils.QueryRunner;

public class JdbcUtils {
    private static ComboPooledDataSource dataSource;
    static {
        dataSource=new ComboPooledDataSource();
    }
    public static QueryRunner getQueryRunner(){
        return new QueryRunner(dataSource);
    }
}

utils工具类的PageBean类

package com.ccx.utils;

import java.util.List;

/**
 * 封装分页的参数
 * @author ccx
 * @param <T>
 */
public class PageBean<T> {
    //当前页,默认显示第一页
    private Integer currentPage=1;
    //每页显示的页数
    private Integer pageCount=4;
    //总记录数,就是数据库的数据总量
    private Integer totalCount;
    //总页数=总记录数/每页显示的页数
    private Integer totalPage;
    //分页查询到的数据
    private List<T> pageData;

    /**
     * 返回总页数
     * @return totalPage
     */
    public Integer getTotalPage(){
        if (totalCount%pageCount==0){
            totalPage=totalCount/pageCount;
        }else{
            totalPage=totalCount/pageCount+1;
        }
        return totalPage;
    }

    public Integer getCurrentPage() {
        return currentPage;
    }

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

    public Integer getPageCount() {
        return pageCount;
    }

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

    public Integer getTotalCount() {
        return totalCount;
    }

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

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

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

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

C3P0的配置文件c3p0-config.xml

<c3p0-config>
	<default-config>
		<property name="jdbcUrl">jdbc:mysql://localhost:3306/test
		</property>
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="user">root</property>
		<property name="password">123456</property>
		<property name="initialPoolSize">3</property>
		<property name="maxPoolSize">6</property>
		<property name="maxIdleTime">1000</property>
	</default-config>
</c3p0-config>

dao层的StudentDaoImp和StudentDao代码如下

package com.ccx.dao;


import com.ccx.entity.Student;
import com.ccx.utils.PageBean;

public interface StudentDaoImp {
    /**
     * 分页查询数据
     * @param pageBean
     */
    public void getAll(PageBean<Student> pageBean);

    /**
     * 查询总记录数
     * @return totalCount
     */
    public Integer getTotalCount();
}

package com.ccx.dao.imp;

import com.ccx.dao.StudentDaoImp;
import com.ccx.entity.Student;
import com.ccx.utils.JdbcUtils;
import com.ccx.utils.PageBean;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import java.util.List;

public class StudentDao implements StudentDaoImp {

    @Override
    public void getAll(PageBean<Student> pageBean) {
        Integer totalCount = this.getTotalCount();
        pageBean.setTotalCount(totalCount);
        Integer currentPage = pageBean.getCurrentPage();
        Integer index=(currentPage-1)*pageBean.getPageCount();
        Integer count=pageBean.getPageCount();
        if(pageBean.getCurrentPage()<=0){
            pageBean.setCurrentPage(1);
        }else if(pageBean.getCurrentPage()>pageBean.getTotalPage()){
            pageBean.setCurrentPage(pageBean.getTotalPage());
        }
        String sql="SELECT * FROM student LIMIT ?,?";
        try{
            QueryRunner queryRunner = JdbcUtils.getQueryRunner();
            List<Student> studentList = queryRunner.query(sql, new BeanListHandler<Student>(Student.class), index, count);
            pageBean.setPageData(studentList);
        }catch(Exception e){
            e.printStackTrace();
        }
    }

    @Override
    public Integer getTotalCount() {
        String sql="SELECT COUNT(1) FROM student";
        try{
            QueryRunner queryRunner = JdbcUtils.getQueryRunner();
            Long query = queryRunner.query(sql, new ScalarHandler<Long>());
            return query.intValue();
        }catch(Exception e){
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
}

service层的StudentServiceImp和StudentService代码如下

package com.ccx.service;

import com.ccx.entity.Student;
import com.ccx.utils.PageBean;


public interface StudentServiceImp {
    /**
     * 分页数据查询
     * @param pageBean
     */
    public void getAll(PageBean<Student> pageBean);
}

package com.ccx.service.imp;

import com.ccx.dao.StudentDaoImp;
import com.ccx.dao.imp.StudentDao;
import com.ccx.entity.Student;
import com.ccx.service.StudentServiceImp;
import com.ccx.utils.PageBean;


public class StudentService implements StudentServiceImp {

    private StudentDaoImp studentDao=new StudentDao();

    @Override
    public void getAll(PageBean<Student> pageBean) {
        try{
            studentDao.getAll(pageBean);
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

controller层的PageAtcion代码如下

package com.ccx.controller;

import com.ccx.entity.Student;
import com.ccx.service.StudentServiceImp;
import com.ccx.service.imp.StudentService;
import com.ccx.utils.PageBean;

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;

@WebServlet("/paging")
public class PagingAction extends HttpServlet {
    private StudentServiceImp service = new StudentService();
    private String url;
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=UTF-8");
        try{
            String currentPage = req.getParameter("currentPage");
            if(currentPage==null||"".equals(currentPage.trim())){
                currentPage="1";
            }
            Integer index= Integer.valueOf(currentPage);
            PageBean<Student> studentPageBean = new PageBean<>();
            studentPageBean.setCurrentPage(index);
            service.getAll(studentPageBean);
            req.setAttribute("pageBean",studentPageBean);
            url="/index.jsp";
        }catch(Exception e){
            e.printStackTrace();
            url="/error.jsp";
        }
        req.getRequestDispatcher(url).forward(req,resp);
    }
}

接下来是展示页面index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
  <head>
    <title>$Title$</title>
    <style type="text/css">
      *{
        margin: 0;
        padding: 0;
      }
      .main{
        width: 800px;
        height: 500px;
        margin: 50px auto;
        background: yellow;
      }
      table{
        width: 800px;
        height: 500px;
        text-align: center;
        font-size: 20px;
      }
      a{
        text-decoration: none;
        color: #000;
        margin-right: 10px;
      }
    </style>
  </head>
  <body>
    <div class="main">
      <table border="1" align="center" cellpadding="5" cellspacing="0">
        <tr>
          <td>序号</td>
          <td>员工编号</td>
          <td>员工姓名</td>
          <td>员工工资</td>
        </tr>
        <!-- 迭代数据 -->
        <c:choose>
          <c:when test="${not empty requestScope.pageBean.pageData}">
            <c:forEach var="stu" items="${requestScope.pageBean.pageData}" varStatus="vs">
              <tr>
                <td>${vs.count }</td>
                <td>${stu.id }</td>
                <td>${stu.name}</td>
                <td>${stu.sal}</td>
              </tr>
            </c:forEach>
          </c:when>
          <c:otherwise>
            <tr>
              <td colspan="4">对不起，没有你要找的数据</td>
            </tr>
          </c:otherwise>
        </c:choose>

        <tr>
          <td colspan="4" align="center">
            当前${requestScope.pageBean.currentPage }/${requestScope.pageBean.totalPage }页     &nbsp;&nbsp;

            <a href="${pageContext.request.contextPath }/paging?currentPage=1">首页</a>
            <a href="${pageContext.request.contextPath }/paging?currentPage=${requestScope.pageBean.currentPage-1}">上一页 </a>
            <a href="${pageContext.request.contextPath }/paging?currentPage=${requestScope.pageBean.currentPage+1}">下一页 </a>
            <a href="${pageContext.request.contextPath }/paging?currentPage=${requestScope.pageBean.totalPage}">末页</a>
          </td>
        </tr>

      </table>
    </div>
  </body>
</html>

运行结果如下