Ajax实现验证(3/4)

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">
<html>
<head>
<title>validation.html</title>
<Meta http-equiv="content-type" content="text/html; charset=UTF-8">
<script language="javascript" type="text/javascript">
var xmlHttp;
function createXMLHttpRequest(){
if(window.ActiveXObject){
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
else if(window.XMLHttpRequest){
xmlHttp = new XMLHttpRequest();
}
}
function validate(){
createXMLHttpRequest();
var date = document.getElementById("birthDate");
var url = "servlet/ValidationServlet?birthDate=" + escape(date.value);
xmlHttp.open("GET",url,true);
xmlHttp.onreadystatechange = callback;
xmlHttp.send(null);
}
function callback(){
if(xmlHttp.readyState == 4){
if(xmlHttp.status == 200){
var mes = xmlHttp.respon***ML.getElementsByTagName("message")[0].firstChild.data;
// alert(xmlHttp.respon***ML.getElementsByTagName("message")[0].firstChild.data);
var val = xmlHttp.respon***ML.getElementsByTagName("passed")[0].firstChild.data;
setMessage(mes,val);
}
}
}
function setMessage(message,isValid){
var messageArea = document.getElementById("dateMessage");
var fontColor = "red";
if(isValid== "true"){
fontColor = "green";
}
messageArea.innerHTML = "<p style=\'color:" + fontColor +"\'>" + message + "</p>";
}
</script>
</head>
<body>
<h2>Ajax validation Example</h2>
Birth Date(MM/dd/yyyy):<input type="text" size="10" id="birthDate" value="11/11/2011" onchange="validate();" />
<div id="dateMessage"></div>
</body>
</html>

package ajax.study;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ValidationServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
PrintWriter out = response.getWriter();
response.setContentType("text/xml");
boolean passed = validateDate(request.getParameter("birthDate"));
response.setHeader("Cache-Control", "no-cache");
String message = "You have entered an invalid date";
if(passed){
message = "You have entered a valid date";
}
out.println("<response>");
out.println("<passed>" + Boolean.toString(passed) + "</passed>");
out.println("<message>" + message +"</message>");
out.println("</response>");
out.close();
}
private boolean validateDate(String date) {
boolean isValid = true;
if(date != null){
SimpleDateFormat formatter = new SimpleDateFormat("MM/dd/yyyy");
try{
formatter.parse(date);
}catch(ParseException pe){
System.out.println(pe.toString());
isValid = false;
}
}
else{
isValid = false;
}
return isValid;
}
public void doPost(HttpServletRequest request, IOException {
doGet(request,response);
}
}

Ajax实现验证(3/4)

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