谢谢，解决了一个问题，这是下一个问题。作为一个新手，我仍然遇到一个错误，简单的应用程序无法正常工作。我得到INVALID_STATE_ERR：当我执行req.open（“Get”，url，true）时，DOM异常11。命令位于以下index.html文件中的javascript中。简单的appl不起作用。我在调试模式下使用chrome，但该应用程序在IE8或FF3上也不起作用。有任何想法吗？INVALID_STATE_ERR：当我执行req.open（“Get”，url，true）时，DOM异常11。
在WindowsVista上使用Eclipse for J2EE和Java6，Ajax。
的index.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<script type="text/javascript">
var req;
function focusIn() {
//This is how you comment in javascript portion of code
//I will now demonstrate an alert function that calls a messagebox to the field, very useful for debugging
//this displays in yoru browser
alert('Hey dad this is an alert, this function was called by the onload message of the Body');
//There is even a cooler way, for instance say you wanted to display values
var two = 2;
var one = 1;
var result = two + one;
//Display your variable result
alert(result);
document.getElementById("key").focus();
}
function convertToDecimal(){
var key = document.getElementById("key");
var keypressed = document.getElementById("keypressed");
keypressed.value = key.value;
// onClick="alert('You clicked the button')"
var url = "/AjaxResponseServlet?key=" + escape(key.value);
if (window.XMLHttpRequest){
req = new XMLHttpRequest();
}
else if (window.ActivateXObject){
req = new ActiveXObject("Microsoft.XMLHTTP")
}
req.open("Get",url,true);
req.onreadystatechange = callback;
req.send(null);
}
function callback() {
if (req.readyState==4) {
if (req.status == 200){
var decimal = document.getElementById("decimal");
decimal.value = req.responseText;
}
}
clear();
}
function clear() {
var key = document.getElementById("key");
key.value="";
}
</script>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Ajax on Java Chapter 2</title>
</head>
<body onload="focusIn();" >
<!-- this is how you comment in HTML Body Portion of the code -->
<h1> AJAX CHARACTER DECODER </h1>
<h2> Press a key to find its value. </h2>
<table>
<tr>
<td>
Enter Key Here --
<input type="text" id="key" name="key" onkeyup="convertToDecimal();" />
</td>
</tr>
</table>
<br />
<table>
<tr>
<td colspan="5" style="border-bottom:solid black 1px;">
Key Pressed:
<input type="text" readonly="readonly" id="keypressed" />
</td>
</tr>
<tr>
<td> Decimal </td>
</tr>
<tr>
<td>
<input type="text" readonly="readonly" id="decimal" />
</td>
</tr>
</table>
<!-- this is how you comment in HTML Body Portion of the code -->
<h1> AJAX CHARACTER DECODER </h1>
<h2> Press a key to find its value. </h2>
<table>
<tr>
<td>
Enter Key Here --
<input type="text" id="key" name="key" onkeyup="convertToDecimal();" />
</td>
</tr>
</table>
<br />
<table>
<tr>
<td colspan="5" style="border-bottom:solid black 1px;">
Key Pressed:
<input type="text" readonly="readonly" id="keypressed" />
</td>
</tr>
<tr>
<td> Decimal </td>
</tr>
<tr>
<td>
<input type="text" readonly="readonly" id="decimal" />
</td>
</tr>
</table>
我当前的web.xml是：
<?xml version="1.0" encoding="UTF-8"?>
http://java.sun.com/XML/NS/JavaEE的/网络app_2_5.xsd” ID = “WebApp_ID” 版本= “2.5”> Ajax2 的index.html index.htm的 的index.jsp default.html中 的default.htm 的Default.jsp AjaxResponseServlet AjaxResponseServlet com.example.servlets.AjaxResponseServlet AjaxResponseServlet /AjaxResponseServlet JAMES JAMES com.example.servlets.JAMES JAMES /JAMES 在这里输入的代码
我的servlet代码是：
/* * 注意到一个字符并将其转换为十进制，并在响应中发回 *值。 */ // package com.oreilly.ajax.servlet; //导致错误，因此注释掉
import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;
公共类AjaxResponseServlet延伸的HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
String key = req.getParameter("key");
if (key != null) {
// extract the first character from key
int keyInt = key.charAt(0);
String decimalString = Integer.toString(keyInt);
// setup the response
res.setContentType("text/xml");
res.setHeader("Cache-Control", "no-cache");
// write out the response string
res.getWriter().write(decimalString);
}
else {
// If key comes back as a null, return a question mark.
res.setContentType("text/xml");
res.setHeader("Cache-Control", "no-cache");
res.getWriter().write("?");
}
}
}