ajax.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>AJAX實例詳解</title>
<script type="text/javascript">
var myRequest;
// 創建XMLHttpRequest對象
function createXMLHttpRequest() {
if(window.ActiveXObject) { // 瀏覽器是否支持ActiveX對象
myRequest = new ActiveXObject("Microsoft.XMLHTTP");
} else if(window.XMLHttpRequest) {
myRequest = new XMLHttpRequest();
}
}
// 建立發送異步數據請求的函數doAjax
function doAjax() {
createXMLHttpRequest(); // 調用創建XMLHttpRequest對象的方法
var username = document.getElementById("username").value; // 獲取文本域中的值
myRequest.open("get", "plain.do?username="+username, true); // 建立對服務器的調用
myRequest.onreadystatechange = updatePage; // 設定處理服務器響應函數
myRequest.send(null); //用get方式建立調用，必鬚髮送null
function updatePage() {
if(myRequest.readyState == 4) { //監視服務器端的狀態改變. 用於測試響應是否已完成
if(myRequest.status == 200) {//獲得服務器的HTTP狀態碼. 用於判斷數據請求是否成功
var data = myRequest.responseText; // 獲取服務器傳遞信息
var res = document.getElementById("message");
res.innerHTML = data;
alert(data); // 通過 responseText 屬性來取回由服務器返回的數據
}
}
}
}
</script>
</head>
<body>
<form action="">
<table>
<tbody>
<tr>
<td>賬號：</td>
<td><input name="username" type="text" id="username" οnchange="doAjax();"></td>
</tr>
<tr>
<td>密碼：</td>
<td><input name="password" type="password"></td>
</tr>
</tbody>
</table>
</form>
<p id="message">註冊成功？？？</p>
</body>
</html>
PlainServlet.java
package com.lian.servlet;
import java.io.IOException;
import java.io.Writer;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class PlainServlet extends HttpServlet {
/*
* 接受請求的服務器端程序
*
*/
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Writer out = resp.getWriter();
String username = req.getParameter("username");
if("test".equals(username)) {
out.write("no");
} else {
out.write("yes");
}
}
}web.xml相應配置
<servlet>
<servlet-name>PlainServlet</servlet-name>
<servlet-class>com.lian.servlet.PlainServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>PlainServlet</servlet-name>
<url-pattern>/plain.do</url-pattern>
</servlet-mapping>