Demo之JavaEE的Web中数据分页显示

[b]JavaWeb分页技术[/b]

关于java web上实现分页技术，方式实际上有很多，也各有特点，此处我只写我的认识。Java web分页无外乎两种，一种直接取出来，放到一个集合了，通过传begin和end参数控制分页，还有一种就是把分页工作交给数据库，让数据库读取需要的begin和end直接的数据。

我使用的是后一种方式就是将分页的工作交给了数据库：我使用的是MySQL数据库

页面显示效果：



页面代码：

<form action="PageServlet" method="post" id="myform">
<table border="1">
<c:forEach items="${pageBean.arrayObjs }" var="obj">
<tr>
<td>${obj }</td>
</tr>
</c:forEach>
<tr>
<td colspan="3">

跳转到：<input id="currentPageNum" type="text" name="currentPageNum" value="${pageBean.currentPageNum }" />
每页记录数：<input type="text" name="pageCount" value="${pageBean.pageCount }" />
<br />
<input type="submit" value="跳转" />
共有${pageBean.totalPage }
<c:if test="${pageBean.previous }">
<a onclick="page(${pageBean.currentPageNum}-1);">上一页</a>
</c:if>
<c:if test="${pageBean.next }">
<a onclick="page(${pageBean.currentPageNum}+1);">下一页</a>
</c:if>
<a onclick="page(${pageBean.totalPage});">最后一页</a>
</td>
</tr>
</table>
</form>

Servlet中的Post方法的代码：

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub

EmpBiz biz=new EmpBiz();

int currentPageNum=1;
int pageCount=4;

String currentPageNumStr=request.getParameter("currentPageNum");

String pageCountStr=request.getParameter("pageCount");
if(currentPageNumStr!=null){

currentPageNum=Integer.parseInt(currentPageNumStr);
}
if(pageCountStr!=null){

pageCount=Integer.parseInt(pageCountStr);
}

PageBean pageBean = biz.lisEmps(currentPageNum, pageCount);

request.setAttribute("pageBean", pageBean);
request.getRequestDispatcher("list.jsp").forward(request, response);
}

在这里自己写了一个存储数据的类PageBean

package com.leejie.page.bean;

import java.util.List;

public class PageBean {

private List arrayObjs;    //从数据库中读出的集合
private int totalCount;            //总条数
private int currentPageNum;            //页数
private int pageCount;            //每页的条数

public PageBean(List arrayObjs,int pageCount,int currentPageNum,int totalCount){

this.arrayObjs=arrayObjs;
this.pageCount=pageCount;
this.currentPageNum=currentPageNum;
this.totalCount=totalCount;
}

public List getArrayObjs() {
return arrayObjs;
}

public void setArrayObjs(List arrayObjs) {
this.arrayObjs = arrayObjs;
}

public int getTotalCount() {
return totalCount;
}

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

public int getPageCount() {
return pageCount;
}

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

public int getCurrentPageNum() {
return currentPageNum;
}

public void setCurrentPageNum(int currentPageNum) {
this.currentPageNum = currentPageNum;
}

public int getTotalPage(){

if(this.totalCount%this.pageCount==0){

return this.totalCount/this.pageCount;
}else{

return this.totalCount/this.pageCount+1;
}
}

public boolean isNext(){

return this.currentPageNum<this.getTotalPage();
}

public boolean isPrevious(){

return this.currentPageNum>1;
}
}

写了一个数据访问层的类EmpBiz：

package com.leejie.page.biz;

import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.leejie.dbcon.util.DBCon;
import com.leejie.page.bean.PageBean;

public class EmpBiz {

public EmpBiz(){

}

public PageBean lisEmps(int currentPageNum,int pageCount){

List emps = new ArrayList();

int a = currentPageNum;
int b = pageCount;
String sql="select * from scores limit ?,?";

PreparedStatement ps=DBCon.getPreparedStatement(sql);
try {

ps.setInt(1, a);
ps.setInt(2, b);
ResultSet rs=ps.executeQuery();
int i=10;
while(rs.next()){

emps.add(i);
i+=5;
}

String sqlTotal="select count(*) from scores";
PreparedStatement psTotal = DBCon.getPreparedStatement(sqlTotal);
int totalCount=0;

ResultSet rsTotal=psTotal.executeQuery();
while(rsTotal.next()){
totalCount=rsTotal.getInt(1);
}

PageBean pageBean=new PageBean(emps, pageCount, currentPageNum, totalCount);

return pageBean;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
DBCon.close();
}
return null;
}
}

还需要用到一个访问数据库的工具类：DBCon，这里也贴出来了：

package com.leejie.dbcon.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class DBCon {

private static final String DRIVERNAME="com.mysql.jdbc.Driver";
private static final String URL="jdbc:mysql://localhost:3306/school";
private static final String USERNAME="root";
private static final String PASSWORD="li257298";

private static Connection conn;
private static PreparedStatement ps;

static{
try {
Class.forName(DRIVERNAME);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

public static Connection getConnection() {

try {
conn=DriverManager.getConnection(URL,USERNAME,PASSWORD);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}

public static PreparedStatement getPreparedStatement(String sql){

try {
ps=getConnection().prepareStatement(sql);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return ps;
}

public static void close(){

if(ps!=null){
try {
ps.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}