<span style="font-family: Arial,Helvetica,sans-serif; background-color: rgb(255,255,255);">今天写了人生第一个ajax，绝对简单通俗，一看就懂。</span>
因为路径问题，还搞了半个小时，所以这是一个菜鸟的进阶。不过想想，ajax这种事情半年前就该学会的。半年前在那个接触各种代码的公司实习的时候就该会这个了，可是对新生事物有种畏惧的感觉，这种心理实在是不该。想想实习也有一年左右了，但是学的东西还是很少。毕设更是还没有开始，总之，继续吧，开始忙毕设了，感觉要炸了。下面是今天做得ajax完整的简单的实例，希望可以对和我一样新人学习有帮助。
随意命名的servlet
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;
public class SelectCityServlet 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 {
response.setContentType("text/xml");
response.setHeader("Cache-Control","no-cache");
String a = "Hello Man!";
// String state = request.getParameter("state");
// StringBuffer sb=new StringBuffer("<state>");
// if ("zj".equals(state)){
// sb.append("<city>hangzhou</city><city>huzhou</city>");
// } else if("zs".equals(state)){
// sb.append("<city>nanjing</city><city>yangzhou</city><city>suzhou</city>");
// }
// sb.append("</state>");
PrintWriter out=response.getWriter();
out.write(a);
out.flush();
out.close();
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @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 doPost(HttpServletRequest request,IOException {
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>SelectCityServlet</servlet-name>
<servlet-class>SelectCityServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>SelectCityServlet</servlet-name>
<url-pattern>/servlet/SelectCityServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
jsp页面，注意url的写法
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<Meta http-equiv="pragma" content="no-cache">
<Meta http-equiv="cache-control" content="no-cache">
<Meta http-equiv="expires" content="0">
<Meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<Meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<script type="text/javascript">
function loadXMLDoc()
{
var xmlhttp;
var str=1;
if (window.XMLHttpRequest)
{// code for IE7+,Firefox,Chrome,Opera,Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6,IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
}
}
xmlhttp.open("GET","servlet/SelectCityServlet",true);
xmlhttp.send();
}
</script>
</head>
<body>
<!-- <select name="state" onChange="getResult(this.value)">-->
<!-- <option value="">Select</option>>-->
<!-- <option value="zj">ZEHJIANG</option>>-->
<!-- <option value="zs">JIANGSU</option>>-->
<!-- </select>-->
<!-- <select id="city">-->
<!-- <option value="">CITY</option>-->
<!-- </select>-->
<div id="myDiv"><h2>使用 AJAX 修改该文本内容</h2></div>
<button type="button" onclick="loadXMLDoc()">修改内容</button>
</body>
</html>
原文链接：https://www.f2er.com/ajax/162373.html