<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!--
以前的那个是老的HTML标准，不是因为浏览器不支持，因为这个网页你告诉浏览器它是老的，
浏览器不会用新的，现在我们用新规范的网页，所以IE浏览器就把它按照新的规范去搞。
其实你可以去大的网站它的的标准老师按照新的。
-->
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<base href="<%=basePath%>">
<style type="text/css">
.odd{background-color: #f3c3f3}
.even{background-color: #c3f3c3}
tr:hover{background-color: #888}
</style>
<script type="text/javascript">
function gotoPage(pid){
var psize = document.getElementById("psize").value;
window.location.href="${pageContext.request.contextPath}/servlet/PageListServlet?pid="+pid+"&psize="+psize;
}
</script>
</head>
<body>
<table width="80%" border="1" style="border-collapse: collapse;" border-color="gray">
<colgroup align="center"></colgroup>
<colgroup align="center"></colgroup>
<c:forEach items="${pageBean.beanList}" var="page" varStatus="status">
<tr class="${status.count%2==1?'odd':'even'}">
<td>
${page.id}
</td>
<td>
${page.name}
</td>
</tr>
</c:forEach>
</table>
总共${pageBean.totalRecords}条记录|每页显示${pageBean.pageSize}
<input id="psize" type="text" value="${pageBean.pageSize}" style="width: 20px" />
|总共有${pageBean.totalPages}页|当前是第${pageBean.currentPage}页
<c:if test="${not pageBean.firstPage}">
<a href="${pageContext.request.contextPath}/servlet/PageListServlet?pid=1">首页</a>
<a href="${pageContext.request.contextPath}/servlet/PageListServlet?pid=${pageBean.previousPage}">上一页</a>
</c:if>
<c:forEach items="${pageBean.pageBar}" var="pageNumber">
<c:if test="${pageNumber==pageBean.currentPage}">${pageNumber}</c:if>
<c:if test="${pageNumber!=pageBean.currentPage}">
<a href="${pageContext.request.contextPath}/servlet/PageListServlet?pid=${pageNumber}">${pageNumber}</a>
</c:if>
</c:forEach>
<c:if test="${not page.lastPage}">
<a href="${pageContext.request.contextPath}/servlet/PageListServlet?pid=${pageBean.nextPage}">下一页</a>
<a href="${pageContext.request.contextPath}/servlet/PageListServlet?pid=${pageBean.totalPages}">尾页</a>
</c:if>
跳转到
<select onchange="gotoPage(this.value)">
<c:forEach begin="1" end="${pageBean.totalPages}" var="pageNumber">
<option value="${pageNumber}" ${pageNumber==pageBean.currentPage?"selected='selected'":""}>${pageNumber}/${pageBean.totalPages}</option>
</c:forEach>
</select>
</body>
</html>
package cn.itcast.servletday13.business.dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.sun.corba.se.spi.presentation.rmi.PresentationDefaults;
import com.sun.org.apache.regexp.internal.recompile;
import cn.itcast.servletday13.business.domain.Page;
import cn.itcast.servletday13.business.util.JdbcUtils;
public class PageDao {
/*
*从第几条开始最多取几条。
*/
public QueryResult getPageQueryResult(int firstRecord,int maxRecords){
QueryResult queryResult = new QueryResult();
queryResult.setTotalRecords(getTotalRecords());
queryResult.setBeanList(getPageData(firstRecord, maxRecords));
return queryResult;
}
/**
* 获取数据库中总记录数
* @return
*/
public int getTotalRecords() {
//获取数据库中总记录数
Connection connection = null;
PreparedStatement statement = null;
ResultSet rs = null;
try {
connection = JdbcUtils.getConnection();//得到连接
String sql = "select count(*) from page";
statement = connection.prepareStatement(sql);//让连接去预编译
rs = statement.executeQuery();//让状态执行。
while (rs.next()) {
return rs.getInt(1);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
JdbcUtils.realase(connection, statement, rs);
}
return 0;
}
/*
*得到每页要显示的数据。
*/
public List<Page> getPageData(int startindex, int pagesize){
Connection connection = null;
PreparedStatement statement = null;
ResultSet rs = null;
List<Page> list = new ArrayList<Page>();
try {
connection = JdbcUtils.getConnection();
String sql = "select * from page limit ?,?";
statement = connection.prepareStatement(sql);
statement.setInt(1, startindex);
statement.setInt(2, pagesize);
rs = statement.executeQuery();
while (rs.next()) {
Page page = new Page();
page.setId(rs.getInt("id"));
page.setName(rs.getString("name"));
list.add(page);
}
} catch (Exception e) {
// TODO: handle exception
}finally{
JdbcUtils.realase(connection, statement, rs);
}
return list;
};
}
package cn.itcast.servletday13.business.dao;
import java.util.List;
public class QueryResult {
private int totalRecords;
private List beanList;
public int getTotalRecords() {
return totalRecords;
}
public void setTotalRecords(int totalRecords) {
this.totalRecords = totalRecords;
}
public List getBeanList() {
return beanList;
}
public void setBeanList(List beanList) {
this.beanList = beanList;
}
@Override
public String toString() {
return "QueryResult [beanList=" + beanList + ", totalRecords="
+ totalRecords + "]";
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result
+ ((beanList == null) ? 0 : beanList.hashCode());
result = prime * result + totalRecords;
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
QueryResult other = (QueryResult) obj;
if (beanList == null) {
if (other.beanList != null)
return false;
} else if (!beanList.equals(other.beanList))
return false;
if (totalRecords != other.totalRecords)
return false;
return true;
}
}
package cn.itcast.servletday13.business.domain;
/**
*
* @author Administrator
* 它是与数据库对应的实体类。
*/
public class Page {
private int id;
private String name;
public Page() {
// TODO Auto-generated constructor stub
}
private Page(int id, String name) {
this.id = id;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
package cn.itcast.servletday13.business.domain;
import java.util.List;
public class PageBean {
/**
* 每次在下面显示几个，其实一般是显示九个，我们数据少显示5个。
*/
private final static int PAGEBARSIZE = 5;
/**
* 数据库中共有多少条记录
*/
private int totalRecords;
/**
* 每页显示几条数据，这个是也是写程序的时间设定的，如果百度搜索就是显示10个。
*/
private int pageSize;//
/**
* 根据数据库中总共的记录数和每页的大小，算出共有多少页。
*/
private int totalPages;
/**
* 显示当前是几页
*/
private int currentPage;
private int previousPage;
private int nextPage;
/**
* 判断是否是第一页
*/
private boolean firstPage;
/**
* 判断是否是最后一页
*/
private boolean lastPage;
/**
* 下面页码条的集合。
*/
private int[] pageBar;
/**
* 所有Bean的集合。
*/
private List beanList;
public int getTotalRecords() {
return totalRecords;
}
public void setTotalRecords(int totalRecords) {
this.totalRecords = totalRecords;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getTotalPages() {
return totalPages;
}
public void setTotalPages(int totalPages) {
this.totalPages = totalPages;
}
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
//?--->100页，结果可能是50页如果只有50页，而我们要到第100页，
// 所以我们要判断，如果超出了则让其到最后 一页，我们不在这里判断 ， 在manager里面调用 。
this.currentPage = currentPage;
}
public boolean isFirstPage() {
return this.currentPage==1;
}
public void setFirstPage(boolean firstPage) {
this.firstPage = firstPage;
}
public boolean isLastPage() {
return this.currentPage==getTotalPages();
}
public void setLastPage(boolean lastPage) {
this.lastPage = lastPage;
}
public int[] getPageBar() {
//除以是为取整，看看是否超出了页码的最大范围，如果没有超出则为0，仍然从
//第一页开始，如果超出了则为1，2，3，4.。。再乘以它，加1，即为开始的页码。
int startPage = (this.currentPage-1)/PAGEBARSIZE*PAGEBARSIZE+1;
int endPage = (this.currentPage-1)/PAGEBARSIZE*PAGEBARSIZE+PAGEBARSIZE;
if(endPage>getTotalPages()){
endPage = getTotalPages();
}
//确定每个页码bar的大小 ，然后赋值。
int[] pageBar = new int[endPage-startPage+1];
for (int i = 0; i < endPage-startPage+1; i++) {
pageBar[i] = startPage+i;
}
return pageBar;
}
public void setPageBar(int[] pageBar) {
this.pageBar = pageBar;
}
public List getBeanList() {
return beanList;
}
public void setBeanList(List beanList) {
this.beanList = beanList;
}
public static int getPagebarsize() {
return PAGEBARSIZE;
}
//不需要那两个属性但是需要这两个方法，它可根据其它算出来。
public int getPreviousPage(){
int previousPage = this.currentPage - 1;
if (previousPage<1) {
previousPage = 1;
}
return previousPage;
}
public int getNextPage(){
int nextPage = this.currentPage + 1;
if (nextPage>getTotalPages()) {
nextPage = totalPages;
}
return nextPage;
}
}
package cn.itcast.servletday13.business.domain;
public class PageInfo {
/**
* 当前是第几页
*/
private int currentPage;
/*
*每页显示多少
*/
private int pageSize;
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
@Override
public String toString() {
return "PageInfo [currentPage=" + currentPage + ", pageSize="
+ pageSize + "]";
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + currentPage;
result = prime * result + pageSize;
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
PageInfo other = (PageInfo) obj;
if (currentPage != other.currentPage)
return false;
if (pageSize != other.pageSize)
return false;
return true;
}
}
package cn.itcast.servletday13.business.manager;
import cn.itcast.servletday13.business.dao.PageDao;
import cn.itcast.servletday13.business.dao.QueryResult;
import cn.itcast.servletday13.business.domain.PageBean;
import cn.itcast.servletday13.business.domain.PageInfo;
public class PageManager {
private PageDao pageDao = new PageDao();
//我们有了PageBean，那么我们需要每个页面的参数。所以有了PageInfo.
public PageBean getCurrentPage(PageInfo info){
int firstRecord = (info.getCurrentPage()-1)*info.getPageSize();
QueryResult queryResult = pageDao.getPageQueryResult(firstRecord, info.getPageSize());
System.out.println(queryResult+"====");
PageBean pageBean = new PageBean();
pageBean.setBeanList(queryResult.getBeanList());
//这个十分巧妙，以前可能用if else 这里用这种更加简单。
int totalPages = (queryResult.getTotalRecords()-1)/info.getPageSize()+1;
pageBean.setTotalPages(totalPages);
int currentPage = info.getCurrentPage();
if (currentPage>totalPages) {
currentPage = totalPages;
}
pageBean.setCurrentPage(currentPage);
pageBean.setPageSize(info.getPageSize());
pageBean.setTotalRecords(queryResult.getTotalRecords());
return pageBean;
}
}
package cn.itcast.servletday13.business.util;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JdbcUtils {
private static String driver = null;
private static String url = null;
private static String username = null;
private static String password = null;
static{
try {
//先从配置里面读取信息
//在类路径下即src下，就通过类加载器来读取。
InputStream inputStream = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
Properties properties = new Properties();
properties.load(inputStream);
driver = properties.getProperty("driver");
url = properties.getProperty("url");
username = properties.getProperty("username");
password = properties.getProperty("password");
System.out.println(driver+url+username+password);
Class.forName(driver);
} catch (Exception e) {
throw new ExceptionInInitializerError();
}
}
public static Connection getConnection() throws SQLException{
return DriverManager.getConnection(url, username, password);
}
public static void realase(Connection connection,Statement statement,ResultSet rs){
if (rs!=null) {
try {
rs.close();
} catch (Exception e2) {
e2.printStackTrace();
}
rs=null;
}
if (statement!=null) {
try {
statement.close();
} catch (Exception e2) {
e2.printStackTrace();
}
statement=null;
}
if (connection!=null) {
try {
connection.close();
} catch (Exception e2) {
e2.printStackTrace();
}
connection=null;
}
}
//
}
package cn.itcast.servletday13.business.web;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.omg.CosNaming.NamingContextExtPackage.StringNameHelper;
import cn.itcast.servletday13.business.domain.PageBean;
import cn.itcast.servletday13.business.domain.PageInfo;
import cn.itcast.servletday13.business.manager.PageManager;
public class PageListServlet extends HttpServlet {
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//这就是MVC，不直接访问通过servelt访问，并且在访问时间把一些东西也转发过去 。
PageManager pageManager = new PageManager();
PageInfo pageInfo = new PageInfo();
String pid = request.getParameter("pid");
int currentPage = 1;
try {
currentPage = Integer.parseInt(pid);
} catch (Exception e) {
// TODO: handle exception
}
String pSize = request.getParameter("psize");
int pageSize = 10 ;//每页显示默认为10。
try {
pageSize = Integer.parseInt(pSize);
} catch (Exception e) {
// TODO: handle exception
}
pageInfo.setCurrentPage(currentPage);
pageInfo.setPageSize(pageSize);
System.out.println(pageInfo.getCurrentPage());
System.out.println(pageInfo.getPageSize());
//写代码先写核心，把最主要的写上，其它都是慢慢添加。下面三句是MVC中最核心的。
PageBean pageBean = pageManager.getCurrentPage(pageInfo);
request.setAttribute("pageBean",pageBean);
request.getRequestDispatcher("/WEB-INF/pageList.jsp").forward(request, response);
}
}
分页步骤：
根据MVC设计模式 将页面记录放在一个javabean对象里面
javabean对象里面的属性则根据页面显示的效果进行设置
谁来创建javabean对象呢？
大的方面来说是servlet创建的javabean对象，小的方面来说
javabean对象是由servlet调用别的模块，通常是service/manger来
创建的.
dao层专门用来处理数据库
业务逻辑层：service/manager层是dao层的上一层，一般传递参数
给dao层
在该分页案例里：
PageManager的输入和输出：
PageManager使用PageInfo（参数对象）对象输出PageBean对象
PageDao层通过SQL语句查询出结果，把查询出的结果输出到
QueryResult对象里.
1.先创建
web,business,business.domain,business.manger,business.dao
几个包
2.在business.domain中创建PageBean.java 完成这个类
根据页面的属性设置PageBean的属性。
PageBean的属性有当前页面数currentPage，总页面数totalPages
，总记录数totalRecoreds，单位页面记录数pageSize，上一页
previousPage，下一页nextPage，是否是第一页firstPage，是否是
最后一页lastPage，页码条数组pageBar，页面记录的集合beanList
完善各个属性对应的setter和getter方法
【】发现问题：当前页面和传入的页面可能发生错误，如只有10页，
却传入了20页，这时就应该把currentPage放在manager里进行处理
.又发现上一页和下一页不需要定义这个属性，可以直接在
getPreviousPage()里设定.
getPageBar()方法：
先设置一个final类型的static的常量PAGEBARSIZE,
定义数组开始时的数字：int startPage = (currentPage-
1)/PAGEBARSIZE*PAGEBARSIZE+1;
定义数组结束时的数字：int endPage = (currentPage-
1)/PAGEBARSIZE*PAGEBARSIZE+PAGEBARSIZE;
再判断endPage
if(endPage>getTotalPages()){
endPage = getTotalPages();
}
再补充这个数组
int[] pageBar = new int[endPage-startPage+1];
3.在business.manager中创建PageManager.java类 完成这个类
pageManager类要返回一个pageBean对象，要想返回pageBean对
象，就得传入一个pageInfo对象，用getCurrentPage(pageInfo
info)方法获得pageBean对象.
所以先在business.manager里创建pageInfo类。
pageInfo类的属性就是传入的当前页面currentPage和单位页面记录
数pageSize.
完成getCurrentPage()方法，需要在方法内部调用一个dao处理数据
库，所以创建一个PageDao类.
在pageDao里设置一个getPageQueryResult()方法，得到结果集
queryResult对象。
注意：把queryResult类设计在dao包里面。里面存放记录总数
totalRecords和记录集合beanList.
我的错误：DAO层要写正确
connection =
JdbcUtils.getConnection();//得到连接
String sql = "select count(*) from
page";
statement =
connection.prepareStatement(sql);//让连接去预编译
rs = statement.executeQuery
();//让状态执行。
根据MVC思想，先访问一个serlvet，然后把该传的数据在这里给它
传进去。
应该把数据放在一个bean里面传进去，那么如何获取这个bean就是
自己要
写的，在页面上用的也这个bean里面的数据。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
这是HTML新规范，这样才能支持更多的。
<style type="text/css">
.odd{background-color: #f3c3f3}
.even{background-color: #c3f3c3}
tr:hover{background-color: #888}
</style>
<script type="text/javascript">
function gotoPage(pid){
var psize =
document.getElementById("psize").value;
window.location.href="${pageContext.request.contextPath}/
servlet/PageListServlet?pid="+pid+"&psize="+psize;
}
</script>
<c:forEach items="${pageBean.beanList}" var="page"
varStatus="status">
<tr class="${status.count%
2==1?'odd':'even'}">
<td>
${page.id}
</td>
<td>
${page.name}
</td>
</tr>
</c:forEach>
html中表格的本质就一个格一个格的，而不是我们看到的表格，
如果我们设置为border=1，那么其实它的表格宽度就是2了。