在这个例子中使用java servlet作为服务器端组件，完成验证日期功能
例子包括2个文件，分别是validation.html和ValidationServlet.java
在html代码里，有一个输入框，相应的onchange事件会触发验证方法。
首先调用createXMLHttpRequest()方法，然后把输入值发送到ValidationServlet.
callback()方法从服务器得到结果，然后委托给setMessage()方法，这个方法会检查值以确定使用什么颜色来显示消息。
以下是完整的源代码：
- <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>validation.html</title>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<script language="javascript" type="text/javascript">
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var xmlHttp;
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function createXMLHttpRequest(){
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if(window.ActiveXObject){
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xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
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}
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else if(window.XMLHttpRequest){
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xmlHttp = new XMLHttpRequest();
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}
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}
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function validate(){
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createXMLHttpRequest();
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var date = document.getElementById("birthDate");
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var url = "servlet/ValidationServlet?birthDate=" + escape(date.value);
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xmlHttp.open("GET",url,true);
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xmlHttp.onreadystatechange = callback;
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xmlHttp.send(null);
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}
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function callback(){
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if(xmlHttp.readyState == 4){
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if(xmlHttp.status == 200){
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var mes = xmlHttp.respon***ML.getElementsByTagName("message")[0].firstChild.data;
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// alert(xmlHttp.respon***ML.getElementsByTagName("message")[0].firstChild.data);
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var val = xmlHttp.respon***ML.getElementsByTagName("passed")[0].firstChild.data;
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setMessage(mes,val);
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}
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}
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}
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function setMessage(message,isValid){
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var messageArea = document.getElementById("dateMessage");
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var fontColor = "red";
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if(isValid== "true"){
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fontColor = "green";
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}
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messageArea.innerHTML = "
+ fontColor +"\'>" + message + "
";
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}
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</script>
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</head>
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<body>
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<h2>Ajax validation Example</h2>
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Birth Date(MM/dd/yyyy):<input type="text" size="10" id="birthDate" value="11/11/2011" onchange="validate();" />
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<div id="dateMessage"></div>
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</body>
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</html>
- package ajax.study;
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import java.io.IOException;
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import java.io.PrintWriter;
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import java.text.ParseException;
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import java.text.SimpleDateFormat;
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import javax.servlet.ServletException;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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public class ValidationServlet extends HttpServlet {
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private static final long serialVersionUID = 1L;
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public void doGet(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException {
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PrintWriter out = response.getWriter();
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response.setContentType("text/xml");
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boolean passed = validateDate(request.getParameter("birthDate"));
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response.setHeader("Cache-Control", "no-cache");
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String message = "You have entered an invalid date";
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if(passed){
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message = "You have entered a valid date";
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}
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out.println("");
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out.println("" + Boolean.toString(passed) + "");
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out.println("" + message +"");
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out.println("");
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out.close();
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}
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private boolean validateDate(String date) {
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boolean isValid = true;
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if(date != null){
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SimpleDateFormat formatter = new SimpleDateFormat("MM/dd/yyyy");
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try{
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formatter.parse(date);
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}catch(ParseException pe){
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System.out.println(pe.toString());
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isValid = false;
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}
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}
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else{
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isValid = false;
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}
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return isValid;
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}
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public void doPost(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException {
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doGet(request,response);
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}
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-
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}
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