Need to conditionally open an additional window from servlet

Question

I thought I had resolved a question I posted earlier after finding this solution: Javascript Post on Form Submit open a new window. However, it doesn't quite do what I want and I can't figure out what's missing.

Here's the issue... I have a jsp with a form in it. When the form is submitted (via JavaScript) I want the parent window to ALWAYS redirect to another page. However, depending on the user's input values, I also CONDITIONALLY want to open another window and redirect THAT window to a different page. So, always redirect parent, sometimes open and redirect child.

My code in the jsp:

<script>
  function handleFormSubmit() {
    var form = document.getElementById("myForm");
    ...
    if (checkbox.checked) {
      // this code creates the child window, but ONLY if the checkbox is checked
      myForm.setAttribute("target", "newResultPage");
      window.open("childpage.jsp", "newResultPage", "width=850,height=550,...");
    }

    form.submit();
  }
</script>

And here's the html form:

<form id='myForm' method='post' action='someAction' accept-charset='UTF-8'>
 // some hidden input elements here
</form>

And the servlet logic:

public class MyServlet extends HttpServlet {

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String redirectedPage = "/parentPage";

    if (someCondition) {
      redirectedPage = "/childpage.jsp";
    }

    RequestDispatcher reqDispatcher = getServletConfig().getServletContext().getRequestDispatcher(redirectedPage);
    reqDispatcher.forward(request,response);
  }
}

When the condition is not met, everything works fine. The servlet is invoked and the calling page is redirected to parentPage. However, if the condition IS met, the servlet correctly opens childpage.jsp in a new child window, but it does NOT redirect the caller page to parentPage.

I've tried adding an explicit redirect("parentPage.jsp"); after form.submit();, but that creates a race condition and is not a good solution since nothing should be called after the form is submitted.

I've also tried modifying the logic inside the servlet, and only redirecting if the condition is detected. However, this causes an issue when the condition isnt' present, since the servlet doesn't know where to send the user next.

Is there a way for me to pass multiple forms to a servlet and handle it via Java? Any help would be greatly appreciated.

-Bob

score 3 · Accepted Answer · answered Jan 09 '13 at 16:55

I figured this out myself a few hours after posting the question, but wanted to make sure the solution worked before writing back.

I recognized that according to my logic, I would always be redirecting the 'parent' page. Thus, rather than trying to open the child window from the original servlet, I moved that logic into the parent page and launched it (conditionally) using the onload function. Here is the updated code to clarify:

Updated jsp code:

<script>
  function handleFormSubmit() {
    var form = document.getElementById("myForm");
    ...
    if (checkbox.checked) {
      // we pass an additional parameter that will make its way to the new parent page
      myForm.setAttribute("launchNow", "1");

      /*
       * this code no longer applies
       */
      // myForm.setAttribute("target", "newResultPage");
      // window.open("childpage.jsp", "newResultPage", "width=850,height=550,...");
    }

    form.submit();
  }
</script>

Html form code (didn't change!):

<form id='myForm' method='post' action='someAction' accept-charset='UTF-8'>
 // some hidden input elements here
</form>

Updated servlet logic:

public class MyServlet extends HttpServlet {

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String redirectedPage = "/parentPage";

    String launchNow = request.getParameter("launchNow");

    if (someCondition) {

      /*
       * Rather than redirecting, we pass an additional params to the new parent page
       */
      // redirectedPage = "/childpage.jsp";

       request.setAttribute("launchNow", launchNow);
       request.setAttribute("anotherParam", someValue);
    }

    RequestDispatcher reqDispatcher = getServletConfig().getServletContext().getRequestDispatcher(redirectedPage);
    reqDispatcher.forward(request,response);
  }
}

Finally, in the new parent jsp page, we check for the additional parameter and act accordingly:

<html>
  <head></head>

  <%
    String launchNow    = request.getParameter( "launchNow" );
    String anotherParam = request.getParameter( "anotherParam" );
  %>

  <body onload="loadOnLaunch(<%= launchNow %>)">
    <form id="hiddenForm" method="post" target="newResultPage" action="anotherAction">
      <input id='anotherParam' type='hidden' name='anotherParam' value='<%= anotherParam %>'/>
    </form>

    <script type='text/javascript'>

      function loadOnLaunch(launchNow) {
        if (launchNow != null && launchNow == "1") {

          /*
           * NOTE: that this block used to reside in the original parent form!
           * It stayed the same, but the action getting called is different
           * thus invoking a different servlet
           */
          var myForm = document.getElementById("hiddenForm");
          myForm.setAttribute("target", "newResultPage");
          window.open("childpage.jsp", "newResultPage", "width=850,height=550,...");
        }
      }

    </script>
    ...
  </body>
</html>

Need to conditionally open an additional window from servlet

1 Answers1