ajax实例01

ajax 实例
项目结构图：

各文件内容如下
Ajax.js：

var xhr;

function createXHR(){
var xhr;
try{
xhr=new ActiveXObject("Msxml2.XMLHTTP");
return xhr;
}catch(e){
try{
   xhr=new ActiveXObject("Microsoft.XMLHTTP");
   return xhr;
}catch(ee){
   xhr=false;
}
}
if(!xhr&&typeof XMLHttpRequest!='undefined'){
xhr=new XMLHttpRequest();
return xhr;
}
return xhr;
}

AjaxServlet01.java:

package com.ajax.hw.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;

/**
* Servlet implementation class AjaxServlet01
*/
public class AjaxServlet01 extends HttpServlet
{
    private static final long serialVersionUID = 1L;

    public AjaxServlet01()
    {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        System.out.println("request!");
        response.setContentType("text/html; charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.print("来自servlet的信息!");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException,
            IOException
    {
        doGet(request, response);
    }

}
test01.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript" src="js/Ajax.js"></script>
<script type="text/javascript">
    var xhr = createXHR();
    xhr.onreadystatechange = onResponse;
    xhr.open("GET", "AjaxServlet01", true);
    xhr.send(null);
    function onResponse2(){
//alert(xhr);
        }
    function onResponse() {
        var obj = xhr;
        if (obj.readyState == 0) {
            document.getElementById("copy").innerHTML = "Sending Request...";
        }
        if (obj.readyState == 1) {
            document.getElementById("copy").innerHTML = "Loading Response...";
        }
        if (obj.readyState == 2) {
            document.getElementById("copy").innerHTML = "Response Loaded...";
        }
        if (obj.readyState == 3) {
            document.getElementById("copy").innerHTML = "Response Ready...";
        }
        if (obj.readyState == 4) {
            if (obj.status == 200) {

                var response = obj.responseText;
                alert("获得的值： "+response);
                alert("123");
                return true;
            } else if (obj.status == 404) {
                // 添加一个定制消息或把用户重定向到另外一个页面
                document.getElementById("copy").innerHTML = "File not found";
            } else {
                document.getElementById("copy").innerHTML = "There was a problem retrieving the XML.";
            }
        }
    };
</script>
</head>
<body>
<span id="copy">
</span>

</body>
</html>

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>ajax00001</display-name>
<welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>def

补充：web前端 , JavaScript ,