function verify(){
// alert("被點擊了。。。。。。。");
//得到id爲loginName的標籤對象
var jqObject = $("#loginName");
//得到文本框中的值
var name = jqObject.val();
//用JQ中的$.get()方法去訪問服務器
/*JQ中的get方法接受的參數
* get(url, [data], [callback], [type])
* url 待載入頁面的URL地址
* data (可選) 待發送 Key/value 參數。
* callback (可選) 載入成功時回調函數。
* type (可選) 返回內容格式，xml, html, script, json, text, _default。
*/
$.get("AjaxTestServlet?loginName=" + name,null,callback);
}
//從服務器返回來的數據封裝在callback函數的參數中
function callback(data){
alert(data);
}主頁html爲如下
<!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=GBK">
<title>Insert title here</title>
<script type="text/javascript" src="jquery-1.7.1.js"></script>
<script type="text/javascript" src="verify.js"></script>
</head>
<body>
<form name="form1" action="AjaxTestServlet" method="POST">
請輸入註冊用戶名： <input name="loginName" type="text" id="loginName">
<input type="button" name="checkLoginName" value="有效性檢查"
οnclick="verify()"><br>
</form>
</body>
</html>接受的響應的服務器端的程序爲AjaxTestServlet
import java.io.IOException;
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 AjaxTestServlet
*/
@WebServlet("/AjaxTestServlet")
public class AjaxTestServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public AjaxTestServlet() {
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
doPost(request,response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// post按doGet()方法處理
response.setContentType("text/html");
PrintWriter out = response.getWriter();
//這裏假設已經註冊過了四位用戶
String[] logined = {"admin","users","dywdyw","zhaom_916"};
//接收從客戶端提交的loginName參數
String loginName = request.getParameter("loginName");
//創建一個存放響應內容的字符串
String responseContext = "true";
for (int i=0;i<logined.length;i++){
//遍歷已註冊用戶列表，如果發現提交的註冊名已存在，則修改響應內容
if (loginName.equals(logined[i]))responseContext = "false";
}
//將處理結果返回給客戶端
out.println(responseContext);
out.flush();
out.close();
}
}