AJAX基础教程－5 Ajax Validate

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>