仿Google分页的经典案例

仿Google分页的经典案例

一般分页的实现有：1、首页、上一页、下一页、最后一页

                                      2、上一页[1][2][3][4][5][6][7][8][9][10]下一页

                                      3、上一页[1][2][3][4][5][6][7]...下一页

下面以：上一页[1][2][3][4][5][6][7][8][9][10]下一页为例，实现一个仿Google得分页。

思路如下：

1、创建Page类，

package cn.csdn.domain;

import java.util.List;

public class Page {

private int nowpage;// 当前页

private int countrecord;// 总记录数

private int countpage;// 总页数

private int pageindex;// 当前页记录开始的位置 (nowpage-1)*PAGESIZE

public static final int PAGESIZE = 5;// 每页显示的记录数

private int sumindex = 6;// 索引的sum值 代表的是 google页面中最大显示页数

private int startindex;// 开始的索引值

private int endindex;// 结束的索引值

private List allentities;

public Page() {

}

public Page(int countrecord, int nowpage) { // 可变

// 计算当前页

this.nowpage = nowpage;

// 计算出当前页开始的位置

this.pageindex = (nowpage - 1) * PAGESIZE;

// 计算总页数

this.countrecord = countrecord;

if (this.countrecord % this.PAGESIZE == 0) {

this.countpage = this.countrecord / this.PAGESIZE;

} else {

this.countpage = this.countrecord / this.PAGESIZE + 1;

}

// 计算索引位置

//==============第一种方法========

/*if (this.nowpage <= 4) {

this.startindex = 1;

this.endindex = this.nowpage + 2;

if(this.endindex>this.countpage){

this.endindex=this.countpage;

}

}else if(this.nowpage>4){

this.startindex=this.nowpage-3;

this.endindex=this.nowpage+2;

if(this.endindex>this.countpage){

this.endindex=this.countpage;

this.startindex=this.countpage-5;

}

}*/

// ============第二种方法==========

if(nowpage<(lastpage-2)){

if(nowpage>=5){

//如果大于6的话，startindex要变大

startindex=nowpage-3;

}else{

startindex=1;

}

//endindex要变大

endindex=nowpage+2;

// 如果总页数小于6

if(endindex>lastpage){

endindex=lastpage;

}

}else{

endindex=lastpage;

startindex=endindex-5;

}

// ======================

}

//get、set方法

public int getNowpage() {

return nowpage;

}

public void setNowpage(int nowpage) {

this.nowpage = nowpage;

}

public int getCountrecord() {

return countrecord;

}

public void setCountrecord(int countrecord) {

this.countrecord = countrecord;

}

public int getCountpage() {

return countpage;

}

public void setCountpage(int countpage) {

this.countpage = countpage;

}

public int getPageindex() {

return pageindex;

}

public void setPageindex(int pageindex) {

this.pageindex = pageindex;

}

public int getSumindex() {

return sumindex;

}

public void setSumindex(int sumindex) {

this.sumindex = sumindex;

}

public int getStartindex() {

return startindex;

}

public void setStartindex(int startindex) {

this.startindex = startindex;

}

public int getEndindex() {

return endindex;

}

public void setEndindex(int endindex) {

this.endindex = endindex;

}

public List getAllentities() {

return allentities;

}

public void setAllentities(List allentities) {

this.allentities = allentities;

}

}

2、dao方法中的代码：

public int getCountRecord() {

// 1、定义返回结果

int countrecord = 0;

// 2、获取数据库连接对象

conn = DBConn.getConn();

// 3、创建预处理的sql语句

String sql = "select count(*) from student";

try {

// 4、根据预处理的sql语句创建预处理的操作对象

pstmt = conn.prepareStatement(sql);

// 5、查询的时候 直接执行

rs = pstmt.executeQuery();

 

// 6、判断

if (rs.next()) {

countrecord = rs.getInt(1);

}

} catch (SQLException e) {

e.printStackTrace();

} finally {

DBConn.close(rs, pstmt);

}

return countrecord;

}

// 获取当前页信息

public List<Student> getNowPageInfo(int pageindex,int pagesize) {

//1、定义返回结果变量

List<Student> allentities = new ArrayList<Student>();

//2、获取连接对象

conn = DBConn.getConn();

 try {

//3、根据预处理的sql语句创建预处理的操作对象

pstmt = conn.prepareStatement("select id,name,age,email from student limit ?,?");

//4、定义下标变量 并赋值

int index = 1;

pstmt.setInt(index++, pageindex);

pstmt.setInt(index++, pagesize);

//5、查询的时候 直接执行

rs = pstmt.executeQuery();

//判断

while(rs.next()){

//创建实体bean对象

Student entity = new Student();

entity.setId(rs.getInt("id"));

entity.setName(rs.getString("name"));

entity.setAge(rs.getInt("age"));

entity.setEmail(rs.getString("email"));

//添加到集合中

allentities.add(entity);

}

 } catch (SQLException e) {

e.printStackTrace();

}finally{

DBConn.close(rs, pstmt);

}

return allentities;

}

3、在servlet中的代码：

protected void doPost(HttpServletRequest req, HttpServletResponse resp)

 

throws ServletException, IOException {

//1.设置编码

req.setCharacterEncoding("utf8");

//2.获取当前页

int nowpage=1;

String npage = req.getParameter("nowpage");

if(npage!=null){

nowpage = Integer.valueOf(npage);

}

//3、创建sevice服务操作对象

StudentServiceImpl ssi = new StudentServiceImpl();

//计算总记录数

int countrecord = ssi.getCountRecord();

//创建page对象

Page stupage = new Page(countrecord, nowpage);

//获取当前页信息

        List<Student> allentities = ssi.getNowPageInfo(stupage.getPageindex(),stupage.PAGESIZE);

//把当前页信息赋值给page对象的list集合

stupage.setAllentities(allentities);

//存入到reqeust中

req.setAttribute("stupage", stupage);

req.getRequestDispatcher("liststudents.jsp").forward(req, resp);

}

4、在jsp中的代码：

<div id="pg">

           <c:if test="${stupage.nowpage!=1}">

           <span>

             <a href="${pageContext.request.contextPath}/liststudents.do?nowpage=${stupage.nowpage-1>0?stupage.nowpage-1:1}">上一页</a>

           </span>

           </c:if>

        <c:forEach begin="${stupage.startindex}" end="${stupage.endindex}" var="indexnum">

           <span>

             [<a href="${pageContext.request.contextPath}/liststudents.do?nowpage=${indexnum}">${indexnum}</a>]

           </span>

         </c:forEach> 

           <c:if test="${stupage.nowpage!=stupage.countpage}">

           <span>

           <a href="${pageContext.request.contextPath}/liststudents.do?nowpage=${stupage.nowpage+1>stupage.countpage?stupage.countpage:stupage.nowpage+1}">下一页</a>

           </span>

           </c:if>

</div>