一个简单的AJAX应用

文件:validation.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >
<html>
 <head>
    <title>Using Ajax for validation</title>
    <script 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 = "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");
            var fontColor = "red";
            if (isValid == "true") {
                fontColor = "green";
            }
            messageArea.innerHTML = "<font color=" + fontColor + ">"
                + message + " </font>";
        }
    </script>
  </head>
  <body>
    <h1>Ajax Validation Example</h1>
    Birth date: <input type="text" size="10" id="birthDate" onchange="validate();"/>
    <div id="dateMessage"></div>
  </body>
</html>

 

文件:ValidationServlet.java

package ajaxbook.chap4;

import java.io.*;
import java.text.ParseException;
import java.text.SimpleDateFormat;

import javax.servlet.*;

import javax.servlet.http.*;
 

public class ValidationServlet extends HttpServlet {
 
    protected void doGet(HttpServletRequest request, HttpServletResponse response)

    throws ServletException, IOException {

        PrintWriter out = response.getWriter();

        //获取
        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();

    }

   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;

    }

}

 

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