Detecting Device Type in a web application

You can get device information by parsing http header

String browserType = request.getHeader("User-Agent");

You should parse browserType to get device type

This may help

  public String  getBrowserInfo( String Information )
  {
    String browsername = "";
    String browserversion = "";
    String browser = Information;
    if (browser.contains("MSIE"))
    {
      String subsString = browser.substring(browser.indexOf("MSIE"));
      String info[] = (subsString.split(";")[0]).split(" ");
      browsername = info[0];
      browserversion = info[1];
    } else if (browser.contains("Firefox"))
    {

      String subsString = browser.substring(browser.indexOf("Firefox"));
      String info[] = (subsString.split(" ")[0]).split("/");
      browsername = info[0];
      browserversion = info[1];
    } else if (browser.contains("Chrome"))
    {

      String subsString = browser.substring(browser.indexOf("Chrome"));
      String info[] = (subsString.split(" ")[0]).split("/");
      browsername = info[0];
      browserversion = info[1];
    } else if (browser.contains("Opera"))
    {

      String subsString = browser.substring(browser.indexOf("Opera"));
      String info[] = (subsString.split(" ")[0]).split("/");
      browsername = info[0];
      browserversion = info[1];
    } else if (browser.contains("Safari"))
    {

      String subsString = browser.substring(browser.indexOf("Safari"));
      String info[] = (subsString.split(" ")[0]).split("/");
      browsername = info[0];
      browserversion = info[1];
    }
    return browsername + "-" + browserversion;
  }

You'll have to read the User-Agent header from the request and decide on that.

In vanilla servlet apps, a crude way of doing it is:

public void doGet(HttpServletRequest request,
                HttpServletResponse response) throws ServletException, IOException {
  if(request.getHeader("User-Agent").contains("Mobi")) {
    //you're in mobile land
  } else {
    //nope, this is probably a desktop
  }
}

You could get a 3rd party software solution. There are plenty of Open Source ones out there. I've used 51Degrees.mobi's Java solution before now (and have also worked on their open source C solution). Follow that link and hit the download button. It's relatively easy to get up and running.