AJAX基础教程－5 Ajax Validate-优快云博客

本文介绍了一个使用Java Servlet进行日期格式验证的示例，并通过Ajax实现客户端与服务器端的交互。该示例展示了如何通过简单的Java代码来判断输入的日期是否符合特定格式，以及如何利用Ajax获取服务器端的响应并更新页面内容。

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java 代码

package ajax.foundations_of_ajax;
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 {
/**
* Handles the HTTP <code>GET</code> method.
*
* @param request
* servlet request
* @param response
* servlet response
*/
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
boolean passed = validateDate(request.getParameter("birthDate"));
response.setContentType("text/xml");
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();
}
/**
* Checks to see whether the argument is a valid date. A null date is
* considered invalid. This method used the default data formatter and
* lenient parsing.
*
* @param date
* a String representing the date to check
* @return message a String representing the outcome of the check
*/
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;
}
}

js 代码

<script type="text/javascript">
var xmlHttp;
//创建xmlHttp对象
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 = "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.responseXML.getElementsByTagName("message")[0].firstChild.data;
var val =
xmlHttp.responseXML.getElementsByTagName("passed")[0].firstChild.data;
setMessage(mes, val);
}
}
}
function setMessage(message, isValid) {
var messageArea = document.getElementById("dateMessage");
fontColor = "";
if (isValid == "true") {
fontColor = "green";
}
messageArea.innerHTML = "<font color=" + fontColor + ">"
+ message + " </font>";
}
</script>