Javascript 学习AJAX,html代码赢得';我什么也不做
我已经为我编写的一个棋盘游戏设置了一个servlet,显示用户名、密码、赢和输。我想创建一个ajax程序来访问这个页面,并创建一个表,列出用户的胜负(就像一个简单的领导委员会)。然而,我的HTML代码将无法工作,我不明白为什么。我可以登录到作为变量url列出的页面,并从servlet中查看xml文件。非常感谢您的帮助Javascript 学习AJAX,html代码赢得';我什么也不做,javascript,html,ajax,Javascript,Html,Ajax,我已经为我编写的一个棋盘游戏设置了一个servlet,显示用户名、密码、赢和输。我想创建一个ajax程序来访问这个页面,并创建一个表,列出用户的胜负(就像一个简单的领导委员会)。然而,我的HTML代码将无法工作,我不明白为什么。我可以登录到作为变量url列出的页面,并从servlet中查看xml文件。非常感谢您的帮助 <html> <head> <script type="text/javascript"> function requestUpdate() {
<html>
<head>
<script type="text/javascript">
function requestUpdate()
{
var req = newXMLHttpRequest();
req.onreadystatechange = function()
{
if(req.readyState == 4)
{
displayResult(req);
}
}
var url = "http://localhost:8080/Checkers/CheckersServlet";
req.open("GET",url,true);
req.send(null);
}
function displayResult(req)
{
var div = document.getElementById("Scoreboard");
div.innerHTML = "<table border> <tr> <th> Username </th> <th> Wins </th> <th> Losses </th> </tr>" ;
var doc = req.responseXML;
var Users = doc.getElementsByTagName('Username');
var Wins = doc.getElementsByTagName('Wins');
var Losses = doc.getElementsByTagName('Losses');
var U;
var W;
var L;
for(var i = 0; i < Users.length; i++)
{
U = Users.item(i).textContent;
W = Wins.item(i).textContent;
L = Losses.item(i).textContent;
div.innerHTML = div.innerHTML + "<tr> <td>" + U + "</td> <td>" + W + "</td> <td>" + L + "</td> </tr>";
}
div.innerHTML = div.innerHTML + "</table>";
}
</script>
</head>
<body onload = "requestUpdate()">
<button onclick = "requestUpdate()">Update</button>
<div id = "Scoreboard"></div>
</body>
函数requestUpdate()
{
var req=newXMLHttpRequest();
req.onreadystatechange=函数()
{
如果(req.readyState==4)
{
显示结果(req);
}
}
变量url=”http://localhost:8080/Checkers/CheckersServlet";
请求打开(“获取”,url,true);
请求发送(空);
}
函数显示结果(req)
{
var div=document.getElementById(“记分板”);
div.innerHTML=“用户名赢了输”;
var doc=req.responseXML;
var Users=doc.getElementsByTagName('Username');
var Wins=doc.getElementsByTagName('Wins');
var损失=文件getElementsByTagName(“损失”);
var U;
var-W;
变种L;
对于(var i=0;i
下面是servlet代码
import java.io.IOException;
import java.io.FileReader;
import java.io.BufferedReader;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class CheckersServlet
*/
@WebServlet("/CheckersServlet")
public class CheckersServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public CheckersServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
// TODO Auto-generated method stub
response.setContentType("text/xml");
PrintWriter out = response.getWriter();
out.println("<?xml version='1.0'?>" );
BufferedReader fReader = new BufferedReader(new FileReader("/Users/adamsturge991/desktop/checkersdatabase.txt"));
String data = fReader.readLine();
out.println("<CheckersData>");
while(data != null)
{
out.println("<User>");
out.println("<Username>");
out.println(data);
out.println("</Username>");
data = fReader.readLine();
out.println("<Password>");
out.println(data);
out.println("</Password>");
data = fReader.readLine();
out.println("<Wins>");
out.println(data);
out.println("</Wins>");
data = fReader.readLine();
out.println("<Losses>");
out.println(data);
out.println("</Losses>");
out.println("</User>");
data = fReader.readLine(); //get next username or null if end of database
}
out.println("</CheckersData>");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
import java.io.IOException;
导入java.io.FileReader;
导入java.io.BufferedReader;
导入java.io.PrintWriter;
导入javax.servlet.ServletException;
导入javax.servlet.annotation.WebServlet;
导入javax.servlet.http.HttpServlet;
导入javax.servlet.http.HttpServletRequest;
导入javax.servlet.http.HttpServletResponse;
/**
*Servlet实现类checkerservlet
*/
@WebServlet(“/checkerservlet”)
公共类checkerservlet扩展了HttpServlet{
私有静态最终长serialVersionUID=1L;
/**
*@参见HttpServlet#HttpServlet()
*/
公共checkerservlet(){
超级();
//TODO自动生成的构造函数存根
}
/**
*@参见HttpServlet#doGet(HttpServletRequest请求,HttpServletResponse响应)
*/
受保护的void doGet(HttpServletRequest请求,HttpServletResponse响应)抛出ServletException,IOException
{
//TODO自动生成的方法存根
setContentType(“text/xml”);
PrintWriter out=response.getWriter();
out.println(“”);
BufferedReader-fReader=new BufferedReader(new FileReader(“/Users/adamsturge991/desktop/checkersdatabase.txt”);
字符串数据=fReader.readLine();
out.println(“”);
while(数据!=null)
{
out.println(“”);
out.println(“”);
out.println(数据);
out.println(“”);
data=fReader.readLine();
out.println(“”);
out.println(数据);
out.println(“”);
data=fReader.readLine();
out.println(“”);
out.println(数据);
out.println(“”);
data=fReader.readLine();
out.println(“”);
out.println(数据);
out.println(“”);
out.println(“”);
data=fReader.readLine();//获取下一个用户名,如果数据库结束,则获取null
}
out.println(“”);
}
/**
*@请参阅HttpServlet#doPost(HttpServletRequest请求,HttpServletResponse响应)
*/
受保护的void doPost(HttpServletRequest请求、HttpServletResponse响应)引发ServletException、IOException{
//TODO自动生成的方法存根
}
}这一行:
var req = newXMLHttpRequest();
新建后需要一个空格,因此:
var req = new XMLHttpRequest();
(还请注意,在displayResult()
函数中不断更新div.innerHTML
不会提供良好的性能。最好在字符串变量中建立所需的html,然后在末尾将div.innerHTML
设置为该变量。)此行:
var req = newXMLHttpRequest();
新建后需要一个空格,因此:
var req = new XMLHttpRequest();
(还请注意,在displayResult()
函数中不断更新div.innerHTML
不会提供良好的性能。最好在字符串变量中建立所需的html,然后在末尾将div.innerHTML
设置为该变量。)此行:
var req = newXMLHttpRequest();
var doc = req.responseXML;
应该是:
var req = new XMLHttpRequest();
var doc = req.responseText;
这一行:
var req = newXMLHttpRequest();
var doc = req.responseXML;
应该是:
var req = new XMLHttpRequest();
var doc = req.responseText;
更新:
var doc = req.responseText;
/*This is for making XML doc, otherwise `getElementsByTagName` wont work*/
if (window.DOMParser)
{
parser=new DOMParser();
xmlDoc=parser.parseFromString(doc,"text/xml");
}
else // Internet Explorer
{
xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async=false;
xmlDoc.loadXML(doc);
}
/*XML DOC is ready, now parse it with `getElementsByTagName1`*/
var Users = xmlDoc.getElementsByTagName('Username');
var Wins = xmlDoc.getElementsByTagName('Wins');
var Losses = xmlDoc.getElementsByTagName('Losses');
这一行:
var req = newXMLHttpRequest();
var doc = req.responseXML;
应该是:
var req = new XMLHttpRequest();
var doc = req.responseText;
这一行:
var req = newXMLHttpRequest();
var doc = req.responseXML;
应该是:
var req = new XMLHttpRequest();
var doc = req.responseText;
更新:
var doc = req.responseText;
/*This is for making XML doc, otherwise `getElementsByTagName` wont work*/
if (window.DOMParser)
{
parser=new DOMParser();
xmlDoc=parser.parseFromString(doc,"text/xml");
}
else // Internet Explorer
{
xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async=false;
xmlDoc.loadXML(doc);
}
/*XML DOC is ready, now parse it with `getElementsByTagName1`*/
var Users = xmlDoc.getElementsByTagName('Username');
var Wins = xmlDoc.getElementsByTagName('Wins');
var Losses = xmlDoc.getElementsByTagName('Losses');
你应该调查一下。对你来说,这会简化大部分工作。你应该调查一下。这将为您简化大部分操作。谢谢!虽然现在我的代码似乎停留在var Users=doc.getElementsByTagName('Username');。我已经检查过了,url上有一些行,比如Adam。知道发生了什么吗?看起来var doc=req.responseXML是空的,我尝试了document.write(doc)来看看会发生什么,它只写了null这个词。我知道document.write()是用来获取字符串的,但是这可能并不意味着任何事情。来自servlet的响应是否具有MIME类型“text/xml”?(另外,不要尝试使用
document.write()
调试console.log()
并打开浏览器控制台查看结果,例如使用Chrome内置的开发工具ctrl-shift-J。)谢谢!虽然现在我的代码似乎停留在var Users=doc.getElementsByTagName('Username');。我已经检查过了,url上有一些行,比如Adam。知道发生了什么吗?看起来var doc=req.responseXML是空的,我尝试了document.write(doc)来看看会发生什么,它只写了null这个词。我知道document.write()是用来获取字符串的,但是这可能并不意味着任何事情。来自servlet的响应是否具有MIME类型“text/xml”?(另外,不要尝试使用document.write()
调试console.log()
并打开浏览器的控制台查看结果,例如,ctrl-shift-J使用Chrome内置的开发工具。)servlet编写的文件是xml文件。是吗