上午比較閑，做了一個ajax的例子，功能是在一個表單中輸入用戶名，光標離開后，到服務器端判斷用戶輸入的名稱是否可用。
1。頁面
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>注冊頁面</title>
<script type="text/javascript">
var xmlHttpRequest = null;
function fValidUserName(){
xmlHttpRequest = init();
var url = "ValidUserName?userName="+document.getElementById("userName");
xmlHttpRequest.open("Get", url, true);
xmlHttpRequest.send(null);
xmlHttpRequest.onreadystatechange=processRequest;
}
function init(){
if(window.XMLHttpRequest){
return new XMLHttpRequest();
}else if(window.ActiveXObject){
return new ActiveXObject("Microsoft.XMLHTTP");
}
}
function processRequest(){
if(xmlHttpRequest.readyState == 4 && xmlHttpRequest.status == 200){
processResponse();
}
}
function processResponse(){
var msg = xmlHttpRequest.responseXML;
var text = msg.getElementsByTagName("Response")[0].firstChild.nodeValue;
var span = document.getElementById("validationMessage");
var html;
if(text == "valid"){
html = "您輸入的用戶名可以使用";
span.style.backgroundColor="#FFCC66";
}else{
html = "您輸入的用戶名已經被使用";
span.style.backgroundColor="#FF0000";
}
span.innerHTML=html;
}
</script>
</head>
<body>
<form action="register">
<table>
<tr><td>用戶名:</td><td><input type="text" name="userName" id="userName" onkeyup="fValidUserName()"><span id="validationMessage" style="background-color:ffcc66"></span></td></tr>
</table>
</form>
</body>
</html> |
2.服務器端：
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ValidUserName extends HttpServlet {
//to fix bug，原來沒有發送xml頭，導致一些不確定的因素發生。
private final String XML_HEAD = "<?xml version=\"1.0\" encoding=\"gbk\"?>";
/**
* Constructor of the object.
*/
public ValidUserName() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* 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");
PrintWriter out = response.getWriter();
out.print(XML_HEAD);//發送xml頭
Random random = new Random(System.currentTimeMillis());
if(random.nextBoolean()){
out.println("<Response>valid</Response>");
System.out.println("valid");
}else{
out.println("<Response>faild</Response>");
System.out.println("not valid");
}
out.flush();
out.close();
}
}
|
文章來源:
http://huxiaofei590.blog.163.com/blog/static/3259612200711612415966