用Ajax实现分页功能的图书购物车

    最近在学习Ajax的过程中，做了一个关于图书的购物车示例，图书的信息保存在服务器端的XML文档中，通过Ajax的异步交互获取XML文件内容，然后在客户端解析XML DOM，最后再在客户端用JS实现简单的分页。
    本人觉得JS文件中的分页做得不是很好，请各位能够多多提点意见，大家共同进步。

效果示例图：



---------------------------以下是基本的文件代码-----------------------------
bookList.xml-->存储书本信息

<?xml version="1.0" encoding="utf-8"?>
<CATALOG>
	<BOOK>
        <Img>001.jpg</Img>
		<BookName>Beginning ASP.NET with C #</BookName>
		<Authors>Hart, Kauffman, Sussman, Ullman</Authors>
		<ISBN>0764588508</ISBN>
		<Price>$39.99</Price>
		<Quantity>50</Quantity>
		<VerYear>1985</VerYear>
	</BOOK>

	<BOOK>
        <Img>002.jpg</Img>
		<BookName>计算机技术集成概论</BookName>
		<Authors>张三牛</Authors>
		<ISBN>0764588509</ISBN>
		<Price>$59.99</Price>
		<Quantity>45</Quantity>
		<VerYear>2001</VerYear>
	</BOOK>

	<BOOK>
        <Img>003.jpg</Img>
		<BookName>操作系统原理</BookName>
		<Authors>李四喜</Authors>
		<ISBN>0764588510</ISBN>
		<Price>$69.99</Price>
		<Quantity>55</Quantity>
		<VerYear>2002</VerYear>
	</BOOK>

	<BOOK>
        <Img>004.jpg</Img>
		<BookName>汇编语言</BookName>
		<Authors>刘也</Authors>
		<ISBN>0764588511</ISBN>
		<Price>$69.99</Price>
		<Quantity>55</Quantity>
		<VerYear>2002</VerYear>
	</BOOK>

	<BOOK>
        <Img>005.jpg</Img>
		<BookName>Oracle 实用开发指南</BookName>
		<Authors>朱五六</Authors>
		<ISBN>0764588513</ISBN>
		<Price>$69.99</Price>
		<Quantity>55</Quantity>
		<VerYear>2002</VerYear>
	</BOOK>

	<BOOK>
        <Img>006.jpg</Img>
		<BookName>Ajax的工作原理</BookName>
		<Authors>李小将</Authors>
		<ISBN>0764588514</ISBN>
		<Price>$69.99</Price>
		<Quantity>55</Quantity>
		<VerYear>2002</VerYear>
	</BOOK>

	<BOOK>
        <Img>007.jpg</Img>
		<BookName>数据结构</BookName>
		<Authors>何伟</Authors>
		<ISBN>0764588515</ISBN>
		<Price>$69.99</Price>
		<Quantity>55</Quantity>
		<VerYear>2002</VerYear>
	</BOOK>

	<BOOK>
        <Img>008.jpg</Img>
		<BookName>SQL Server开发指南</BookName>
		<Authors>耿文化</Authors>
		<ISBN>0764588516</ISBN>
		<Price>$69.99</Price>
		<Quantity>55</Quantity>
		<VerYear>2002</VerYear>
	</BOOK>
</CATALOG>

Cart.js-->异步交互的JS文件

var xmlHttpRequest;

var currentPage = 0;//记录当前页索引
var everyPageCount = 3;//每页显示的项目数量
var maxPageCount = 0;//记录最大页数
var bookIndex = -1;//当前BOOK元素的索引

var result = null;//服务器返回的XML文档对象
var bookNodes = null;//储存所有BOOK节点对象

//创建一个用来和服务端交互的Ajax核心对象XMLHttpRequest
function createXMLHttpRequest(){
	if(window.XMLHttpRequest){
		xmlHttpRequest = new XMLHttpRequest();
		if(xmlHttpRequest.overrideMimeType){
			xmlHttpRequest.overrideMimeType("text/xml");
		}
	}
	else if(window.ActiveXObject){
        xmlHttpRequest = new ActiveXObject("Microsoft.XMLHTTP");
	}
}

//使用传统的注册事件模型注册按钮
function registerButtonEvent(){
    document.getElementById("previousPage").onclick = sendPreviousPage;
    document.getElementById("nextPage").onclick = sendNextPage;
}

//购物车页面初始化
function sendRequest(){
    registerButtonEvent();//注册页面的按钮事件
    createXMLHttpRequest();//创建XMLHttpRequest对象

    //异步加载XML文档数据
    xmlHttpRequest.open("GET", "bookList.xml?id=" + Number(new Date), true);

    //指定回调函数
    xmlHttpRequest.onreadystatechange = getInitData;

    xmlHttpRequest.send(null);
}

//页面初始化回调函数从服务器端获取XML文档数据并解析
function getInitData(){
	if(xmlHttpRequest.readyState == 4 && xmlHttpRequest.status == 200){
        //alert("Server Success!");
        result = xmlHttpRequest.responseXML;
        bookNodes = result.getElementsByTagName('BOOK');
        //alert("bookNodes.length=" + bookNodes.length);
        if(currentPage == 0 && bookNodes.length == 0){
            document.getElementById("info").innerHTML = "很抱歉,未找到相关数据!";
            document.getElementById("maxPageCount").innerHTML = 0;
            document.getElementById("currentPage").innerHTML = 0;
            return;
        }
        else{
            //判断并获取最大页数
            //alert(parseInt(bookNodes.length/everyPageCount));
            maxPageCount = bookNodes.length%everyPageCount==0?parseInt(bookNodes.length/everyPageCount):parseInt(bookNodes.length/everyPageCount+1);
            document.getElementById("maxPageCount").innerHTML = maxPageCount;
            sendNextPage();
        }

    }
}

//前一页按钮
function sendPreviousPage(){
    var pageFirstItem = 0;//记住上一页的第一项的索引
    if(bookIndex%3 == 0){
        pageFirstItem = bookIndex - everyPageCount * 2 + 2;
    }
    else if(bookIndex%3 == 1){
        pageFirstItem = bookIndex - everyPageCount * 2 + 1;
    }
    else if(bookIndex%3 == 2){
        pageFirstItem = bookIndex - everyPageCount * 2;    
    }

    if(currentPage == 0 || currentPage == 1){
        alert("当前页已经是第一页!");
        return;
    }
    
//    if(pageFirstItem < -1){
//        alert("当前页已经是第一页!");
//        return;
//    }

    if(pageFirstItem >= -1){
        bookIndex = pageFirstItem;
        currentPage--;
        document.getElementById("currentPage").innerHTML = currentPage;
        for(var i = 0; i < everyPageCount; i++){
            var imgTag = "img" + (i+1).toString();
            var desTag = "des" + (i+1).toString();
            if(bookIndex < bookNodes.length - 1){
                bookIndex++;
                displayItem(bookIndex,imgTag,desTag,1);
            }
            else{
                displayItem(bookIndex,imgTag,desTag,0);
            }
        }
    }
}

//下一页按钮
function sendNextPage(){
    var pageEndItem = bookIndex + everyPageCount;//下一页面最后一项的索引
    
    if(pageEndItem <= bookNodes.length + 1){
        currentPage++;
        document.getElementById("currentPage").innerHTML = currentPage;
        for(var i = 0; i < everyPageCount; i++){
            var imgTag = "img" + (i+1).toString();
            var desTag = "des" + (i+1).toString();
            if(bookIndex < bookNodes.length - 1){
                bookIndex++;
                displayItem(bookIndex,imgTag,desTag,1);
            }
            else{
                displayItem(bookIndex,imgTag,desTag,0);
            }
        }
    }
//    else if(currentPage + 1 == maxPageCount){
//        alert("当前页是最后一页!");
//        return;
//    }
    else if(pageEndItem > bookNodes.length){
        alert("当前页是最后一页!");
        return;
    }
}

//显示指定索引的BOOK项目到指定的页面位置
function displayItem(bookIndex,imgTag,desTag,flag){
    if(flag == 1){
        var imgString = null;
        var desString = null;
        var bookImg = bookNodes[bookIndex].getElementsByTagName("Img")[0].childNodes[0].nodeValue;
        //alert(bookImg);
        var bookName = " 书名: " + bookNodes[bookIndex].getElementsByTagName("BookName")[0].childNodes[0].nodeValue;
        var authors = " 作者: " + bookNodes[bookIndex].getElementsByTagName("Authors")[0].childNodes[0].nodeValue + "<br/>";
        var isbn = " 出版号: " + bookNodes[bookIndex].getElementsByTagName("ISBN")[0].childNodes[0].nodeValue + "<br/>";
        var price = " 出版年: " + bookNodes[bookIndex].getElementsByTagName("VerYear")[0].childNodes[0].nodeValue + "<br/>";
        var quantity = " 价格: " + bookNodes[bookIndex].getElementsByTagName("Price")[0].childNodes[0].nodeValue + "<br/>";
        var varYear = " 库存数量: " + bookNodes[bookIndex].getElementsByTagName("Quantity")[0].childNodes[0].nodeValue + "<br/>";

        imgString = "<img src=\"" + bookImg + "\"/>";

        desString = bookName + "<br/>";
        desString += authors;
        desString += isbn;
        desString += varYear;
        desString += price;
        desString += quantity;
        
        desString += "<a href=\"#\" onclick=\"addRemoveItem('add','" + bookName + "')\">" + "将这本书加入购物车(购买)</a>";
        //alert("<a href=\"#\" onclick=\"addRemoveItem('add','" + bookName + "')\">" + "将这本书加入购物车(购买)</a>");

        document.getElementById(imgTag).innerHTML = imgString;
        document.getElementById(desTag).innerHTML = desString;
    }
    else{
        document.getElementById(imgTag).innerHTML = "";
        document.getElementById(desTag).innerHTML = "";
    }
}

//利用服务器Session保存购物车内容
function addRemoveItem(action,bookName){
    if(action == 'add'){
        var url = "/ManageCartServlet?action=" + action + "&bookName=" +encodeURIComponent(bookName) + "&value=" + Number(new Date);
        xmlHttpRequest.open("GET", url, true);
        xmlHttpRequest.onreadystatechange = getData;
        xmlHttpRequest.send(null);
    }
    else{
        var url = "/ManageCartServlet?action=" + action + "&bookName=" +encodeURIComponent(bookName) + "&value=" + Number(new Date);
        xmlHttpRequest.open("GET", url, true);
        xmlHttpRequest.onreadystatechange = getData;
        xmlHttpRequest.send(null);
    }
}

//回调函数从服务器端获取结果数据并解析
function getData(){
	if(xmlHttpRequest.readyState == 4 && xmlHttpRequest.status == 200){
        //alert("Server Success!");
        var result = xmlHttpRequest.responseXML;
        var bookNodes = result.getElementsByTagName('BOOK');
        var bookNameNodes = result.getElementsByTagName('BookName');
        var quantityNodes = result.getElementsByTagName('Quantity');

        var spantag = document.getElementById('cart');
        spantag.innerHTML = "";

        for(var i = 0; i < bookNodes.length; i++){
            if(window.ActiveXObject){
                spantag.innerHTML += " " + bookNodes[i].firstChild.text;
                spantag.innerHTML += " --> ";
                spantag.innerHTML += " " + bookNodes[i].lastChild.text;
                spantag.innerHTML += "  ";
                spantag.innerHTML += " " + "<a href=\"#\" onclick=\"addRemoveItem('remove','" + bookNodes[i].firstChild.text + "')\">" + "从购物车删除这本书</a>";
                spantag.innerHTML += "<br/>";
            }
            else{
                spantag.innerHTML += " " + bookNameNodes[i].firstChild.nodeValue;
                //spantag.innerHTML += " " + bookNodes[1].firstChild.textContent;
                spantag.innerHTML += " --> ";
                spantag.innerHTML += " " + quantityNodes[i].firstChild.nodeValue;
                //spantag.innerHTML += " " + bookNodes[1].firstChild.textContent;
                spantag.innerHTML += "  ";
                spantag.innerHTML += " " + "<a href=\"#\" onclick=\"addRemoveItem('remove','" + bookNameNodes[i].firstChild.nodeValue + "')\">" + "从购物车删除这本书</a>";
                spantag.innerHTML += "<br/>";
            }
        }
    }
}

Cart.html-->页面显示使用的HTML文件

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
        "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <title>购物车示例</title>
    <script type="text/javascript" src="Cart.js"></script>
</head>
<body onload="sendRequest()">
    总共<span id="maxPageCount"></span>页----当前第<span id="currentPage"></span>页
    <hr size="1"/>
    <div id="info"></div>
    <table>
        <tr>
            <td><div id="img1"></div></td>
            <td><div id="img2"></div></td>
            <td><div id="img3"></div></td>
        </tr>
        <tr>
            <td><div id="des1"></div></td>
            <td><div id="des2"></div></td>
            <td><div id="des3"></div></td>
        </tr>
    </table>
    <br/>
    <input type="button" id="previousPage" value="前一页"/>
    <input type="button" id="nextPage" value="下一页"/>
    
    <hr size="1"/>
    <h3>您的购物车:</h3><br/>
    <span id="cart"></span>
</body>
</html>

ManageCartServlet.java-->实现购物车信息存储的Servlet文件

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.ServletException;
import java.io.IOException;
import java.util.Hashtable;
import java.util.Iterator;

public class ManageCartServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action")==null?"":request.getParameter("action");
        //System.out.println("action:" + action);
        String newItem = request.getParameter("bookName")==null?"":request.getParameter("bookName");
        //System.out.println("newItem:" + newItem);

        HttpSession session = request.getSession(true);
        Hashtable ht = new Hashtable();
        String cartXml = "";
        
        //当前已经处于购物页面,并且已经处于购物状态.
        if(session.getAttribute("cart") != null){
            //System.out.println("已经处于购物状态");
            ht = (Hashtable)session.getAttribute("cart");

            //添加购物项目
            if("add".equals(action)) {
                //已经存在于购物车中的项目
                if(ht.containsKey(newItem)){
                    Integer count = (Integer)ht.get(newItem);
                    count ++;
                    ht.put(newItem, new Integer(count));
                    session.setAttribute("cart", ht);

                    cartXml = toXml(ht);
                    response.setContentType("text/xml");
					response.getWriter().write(cartXml);
                }
                //购物车中不存在的项目,现在新增加.
                else{
                    ht.put(newItem, new Integer(1));
                    session.setAttribute("cart", ht);

                    cartXml = toXml(ht);
                    response.setContentType("text/xml");
					response.getWriter().write(cartXml);
                }
            }

            //删除购物项目
            else if("remove".equals(action)){
                //System.out.println(ht == null);
                Integer count = (Integer)ht.get(newItem);
                //System.out.println(count == null);
                count --;
                if(count == 0){
                    ht.remove(newItem);
                }
                else{
                    ht.put(newItem, new Integer(count));
                }
				session.setAttribute("cart", ht);
				cartXml = toXml(ht);
				response.setContentType("text/xml");
				response.getWriter().write(cartXml);
            }
        }
        //初次进入购物页面
        else{
            //System.out.println("初次进入购物页面");
			ht.put(newItem, 1);
			session.setAttribute("cart", ht);
			cartXml = toXml(ht);
			response.setContentType("text/xml");
			response.getWriter().write(cartXml);
        }
        //System.out.println(cartXml);
    }

    //将集合的内容转换为字符串形式组成的XML数据
    public String toXml(Hashtable ht)
	{
		StringBuffer xmlDoc = new StringBuffer();
		xmlDoc.append("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n");
		xmlDoc.append("<CART>\n");

		for (Iterator iter = ht.keySet().iterator(); iter.hasNext();)
		{
			String item = (String)iter.next();
			int Quantity = ((Integer)ht.get(item)).intValue();
			xmlDoc.append("<BOOK>\n");
			xmlDoc.append("<BookName>");
			xmlDoc.append(item);
			xmlDoc.append("</BookName>\n");
			xmlDoc.append("<Quantity>");
			xmlDoc.append(Quantity);
			xmlDoc.append("</Quantity>\n");
			xmlDoc.append("</BOOK>\n");
		}
		xmlDoc.append("</CART>\n");
		return xmlDoc.toString();
	}
}

备注：示例中使用的图片请在附件中下载！

部署说明：所有源代码以及相关文件在附件上传，只需要在IDE工具中根据以往的Java Web项目创建，然后拷贝文件到src和WebRoot就OK了。。。

初学Ajax，好好研究前辈们的杰作