Ajax基础 (二)

最新推荐文章于 2025-09-05 23:01:36 发布

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最新推荐文章于 2025-09-05 23:01:36 发布

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分类专栏： Ajax 文章标签： ajax date xmlhttprequest function servlet callback

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Ajax应用

4.1 完成验证：

范例：日期验证

Web端：

<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);
        }

    </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>

Server端：

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

import javax.servlet.*;
import javax.servlet.http.*;

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 represnting 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;
    }
}