<script type="text/javascript">
    function loadXMLDoc(username) {
        var xmlhttp;
        if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
            xmlhttp = new XMLHttpRequest();
        } else {// code for IE6, IE5
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }

        xmlhttp.onreadystatechange = function() {
            if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                var text = xmlhttp.responseText;
                if (text == "1") {
                    document.getElementById("myDiv").innerHTML = xmlhttp.responseText;
                }
            }
        }
        xmlhttp.open("GET", "Demo", true);
        xmlhttp.send(null);
    }
</script>

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("ooo v587");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("1");
        out.flush();
        out.close();
    }

<servlet>
        <description>This is the description of my J2EE component</description>
        <display-name>This is the display name of my J2EE component</display-name>
        <servlet-name>Demo</servlet-name>
        <servlet-class>Filter.Demo</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>Demo</servlet-name>
        <url-pattern>/servlet/Demo</url-pattern>
    </servlet-mapping>