案例:怎样使用java实现分页处理?

Posted 2020-09-25 波光闪烁

数据库表格:

　　customer

 

分页的实现:

从数据库查询--总记录：totalRecords

自定义--每页显示多少条记录： pageSize

通过总记录数和页容量计算出来--总页数： totalPages ----(totalRecords%pageSize==0? totalRecords/pageSize : totalRecords/pageSize+1)

页面传递--当前页码: currentPage

从数据库查询--每页数据：List

通过当前页数和页容量计算出来--每页查询开始的索引 startIndex startIndex = (currentPage-1)*pageSize

bean

public class Page {
    private long totalRecords;//总记录数   从数据库查询
    private long pageSize=5;//每页显示多少条 
    private long totalPages;//总页数    计算出来
    private long currentPage;//当前页码  
    private List list; //每页存放的数据   从数据库查询
    private long startIndex;//每页开始查询的索引 计算出来
    
    public Page(long currentPage,long totalRecords){
        this.currentPage = currentPage;
        this.totalRecords = totalRecords;
        this.totalPages = (totalRecords%pageSize==0?  totalRecords/pageSize : totalRecords/pageSize+1);
        this.startIndex = (currentPage-1)*pageSize;
    }

    public long getTotalRecords() {
        return totalRecords;
    }

    public void setTotalRecords(long totalRecords) {
        this.totalRecords = totalRecords;
    }

    public long getPageSize() {
        return pageSize;
    }

    public void setPageSize(long pageSize) {
        this.pageSize = pageSize;
    }

    public long getTotalPages() {
        return totalPages;
    }

    public void setTotalPages(long totalPages) {
        this.totalPages = totalPages;
    }

    public long getCurrentPage() {
        return currentPage;
    }

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

    public List getList() {
        return list;
    }

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

    public long getStartIndex() {
        return startIndex;
    }

    public void setStartIndex(long startIndex) {
        this.startIndex = startIndex;
    }
    
    
}

Dao.Impl

public class CustomerDaoImpl implements CustomerDao{
    QueryRunner qr = new QueryRunner(C3p0Util.getDataSource());
    //显示列表
    public List<Customer> findCustomers() {
        String sql = "select * from customer";
        List<Customer> clist = new ArrayList<Customer>();
        try {
            clist = qr.query(sql, new BeanListHandler<Customer>(Customer.class));
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return clist;
    }
    //查询每页记录数据
    public List<Customer> findPageCustomers(long startIndex, long pageSize) {
        String sql = "select * from customer limit ?,?";
        Object[] params = {startIndex,pageSize};
        List<Customer> clist = new ArrayList<Customer>();
        try {
            clist = qr.query(sql, new BeanListHandler<Customer>(Customer.class),params);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return clist;
    }
    //查询总记录数
    public long findCustomersCount() {
        String sql  = "select count(1) from customer";
        long  i= 0;
        try {
            i = (Long)qr.query(sql, new ScalarHandler(1));
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return i;
    }
}

Service.Impl

public class CustomerServiceImpl implements CustomerService{
    private CustomerDao dao = new CustomerDaoImpl();
    //显示列表
    public List<Customer> findCustomers() {
        return dao.findCustomers();
    }
    //与页码相对应的每个列表
    public Page findPage(long currentPage) {
        long totalRecords = dao.findCustomersCount();//总记录数
        Page page = new Page(currentPage, totalRecords);
        List<Customer> clist = dao.findPageCustomers(page.getStartIndex(), page.getPageSize());
        page.setList(clist);
        return page;
    }
}

Servlte(在web.xml里设置默认页面为servlte页面)

/**
 * servlet页面
 * @author Administrator
 *下午1:56:49
 */
public class CustomerAction extends HttpServlet {
    private CustomerService service = new CustomerServiceImpl();
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String currentPageStr = request.getParameter("pagenum"); //从网页上获取跳转的页数
        int currentPage = 1;  //默认显示第一页
        if(currentPageStr!=null){
            currentPage = Integer.parseInt(currentPageStr);
        }
        Page page = service.findPage(currentPage);//显示与页码相对应的列表
        request.setAttribute("page", page);
        request.getRequestDispatcher("WEB-INF/jsp/clist.jsp").forward(request, response);
        
    }

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

}

jsp(由servlet处理后转发至jsp页面)

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>客户列表</title>
<c:set var="ctp" value="${pageContext.request.contextPath }"></c:set>
<script type="text/javascript" src="${ctp }/js/jquery-1.8.3.js"></script>
</head>
<body>
    <h2>客户列表</h2>
    <table border="1" width="80%">
        <tr>
            <th>序号</th>
            <th>姓名</th>
            <th>性别</th>
            <th>生日</th>
            <th>电话</th>
            <th>邮箱</th>
            <th>爱好</th>
            <th>类型</th>
            <th>描述</th>
        </tr>
        <c:forEach items="${page.list }" var="ct" varStatus="cs">     <!--使用迭代标签库 -->
            <tr style="background-color: ${cs.count%2==0? \'#E0FFFF\':\'#EEE685\'}">
                <td>${cs.count }</td>
                <td>${ct.name }</td>
                <td>${ct.gender==1? \'男\':\'女\' }</td>
                <td>${ct.birthday }</td>
                <td>${ct.phone }</td>
                <td>${ct.email }</td>
                <td>${ct.hobby }</td>
                <td>${ct.type }</td>
                <td>${ct.description }</td>
            </tr>
        </c:forEach>
    </table>
    <p>
        总记录数：${page.totalRecords }条
        当前第${page.currentPage }页/共${page.totalPages }页
        <a href="${ctp }/customerAction?pagenum=1">首页</a>
        <a href="${ctp }/customerAction?pagenum=${page.currentPage-1<1? 1 : page.currentPage-1}">上一页</a>
        <a href="${ctp }/customerAction?pagenum=${page.currentPage+1<page.totalPages? page.currentPage+1 : page.totalPages}">下一页</a>
        <a href="${ctp }/customerAction?pagenum=${page.totalPages}">尾页</a>
        <input id="num" placeholder="请输入整数"/><input type="button" id="btn" value="跳转"/>
        <input id="pages" value="${page.totalPages }" type="hidden">
    </p>
    <!--使用jQuery简单判定跳转的页数是否合法-->
    <script type="text/javascript">
        $(function(){
            $("#btn").click(function(){
                var pageNum = Number($("#num").val());
                var pages = Number($("#pages").val());
                if(isNaN(pageNum)){
                    alert("请输入数字！");
                    return;
                }
                if(pageNum > pages){
                    alert("输入页码错误！");
                    return;
                }
                location.href = "${ctp}/customerAction?pagenum="+pageNum;
            });
        });
    </script>
    
</body>
</html>

 

效果图:

注:省略dao层、service层、c3p0连接池工具包