Update an HTML Form Using an XML ActiveX Object and a Servlet

The minimum requirement for this tip to work is to have Internet Explorer with MSXML objects installed when Windows is installed. The DOMDocument is also available in the new versions of Netscape. This example displays user information based on the login id without submitting the form.

Create a servlet that will submit an .xml document based on the request parameter "login" value:


import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class UserInfoServlet
    extends HttpServlet {
  private static final String CONTENT_TYPE = "text/xml";

  //Process the HTTP Get request
  public void doGet(HttpServletRequest request, HttpServletResponse response) throws
      ServletException, IOException {
    doPost(request, response);
  }

  //Process the HTTP Post request
  public void doPost(HttpServletRequest request, HttpServletResponse response) throws
      ServletException, IOException {
    String login = request.getParameter("login");
    String info = null;
    if (login != null && "guest".equalsIgnoreCase(login)) {
      info = "<username>Guest</username>";
    }
    else {
      info = "<username>Unknown</username>";
    }
    response.setContentType(CONTENT_TYPE);
    PrintWriter out = response.getWriter();
    out.println("<?xml version=\"1.0\"?>");
    out.println("<output>");
    out.println(info);
    out.println("</output>");
  }
}

Add servlet mapping for this servlet in the web.xml file as follows:


<servlet>
  <servlet-name>userinfo</servlet-name>
  <servlet-class>UserInfoServlet</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>userinfo</servlet-name>
  <url-pattern>/ui</url-pattern>
</servlet-mapping>

Following is the HTML page:


<html>
  <head><title>User Information</title></head>
  <body>
    <form name="userinfo">
      Enter Login Id:
      <input type="text" name="login" onblur="javascript:doLoadData(this.value)" />
      User Information: (Readonly)
      <input type="text" name="username" readonly="readonly" />
    </form>
  </body>

  <script language="JavaScript1.4" type="text/javascript">
  function doLoadData(login) {
    var dd = new ActiveXObject("MSXML.DOMDocument");
    dd.async = false;
    dd.load('/context/ui?login=' + login);
    var node = dd.documentElement.selectSingleNode("/output/username");
    document.forms['userinfo'].elements['username'].value = node.text;
  }
  </script>

</html>

Now, if you type "guest" in the login input, "Guest" or otherwise Unknown will be displayed automatically.

Farukh Ijaz

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