model view controller - How to develop JSP/Servlets Web App using MVC pattern?

Question

I'm developing a JSP/Servlet web app (no frameworks). I want to use MVC pattern. I am going to design my project like this:

1. Controller: a servlet that reads a request, extracts the values,communicates with model objects and gives information to a JSP page.
2. View: JSP Pages.
3. Model: Java Classes / Java Beans .. etc.

The problem: Index.jsp is the starting point (default page) in my web site. So, the Index.jsp becomes the controller to parse the request. For example, the following request:

index.jsp?section=article&id=10

is parsed in index.jsp as following :

<div class="midcol">
<!-- Which section? -->
<%String fileName = request.getParameter("section");
if (fileName == null) {
fileName = "WEB-INF/jspf/frontpage.jsp";
} else {
fileName = "WEB-INF/jspf/" + fileName + ".jsp";
}
%>
<jsp:include page='<%= fileName%>' />
</div>

Here, I can't force the servlet to be a controller, because the index.jsp is the controller here since it's the starting point.

Is there any solution to forward the request from index.jsp to the servlet and then go back to index.jsp? Or any solution that achieves the MVC goal - the servlet should be the controller?

I'm thinking of making a FrontPageController servlet as default page instead of index.jsp, but I don't know if it's a perfect idea?

Answer 1

Get rid of index.jsp and just let the controller servlet listen on a specific url-pattern of interest. The controller itself should forward the request to the JSP page of interest using RequestDispatcher.

request.getRequestDispatcher("/WEB-INF/page.jsp").forward(request, response);

Alternatively you can let index.jsp forward or redirect to an URL which is covered by the controller servlet which in turn shows the "default" page (which seems to be frontpage.jsp).

That said, in a correct MVC approach, you should have no scriptlets in JSP files. Whenever you need to write some raw Java code inside a JSP file which can't be replaced reasonably by taglibs (JSTL and so on) or EL, then the particular Java code belongs in any way in a real Java class, like a Servlet, Filter, Javabean, etcetera.

With regard to the homegrown MVC approach, you may find this answer and this article useful as well.