Question

I’m learning JSP and I want to include subpage (on div named “content”) based on GET method generated by menu link.

<div id="menu">
   <a href="/index.jsp?page=1">Subpage 2</a>
</div>
<div id="content>

   //include somehow subpage s2.sjp

</div>

I’ve done somethink like that:

    <%
            int par = 0;
            String which = "blank.jsp" ;
            if (request.getParameter("page") != null) {
                par = Integer.valueOf(request.getParameter("page"));
            }
                switch (par) {
                    case 0:
                        which = "blank.jsp";
                        break;
                    case 1:
                        which = "s2.jsp";
                        break;
                }

    %>

but I’m not sure if that is proper way to solve my problem in JSP.

Answer 1

You can just use EL in <jsp:include>.

<jsp:include page="/WEB-INF/${param.page}.jsp" />

Calling foo.jsp?page=bar will let ${param.page} resolve to bar and this <jsp:include> will then effectively include /WEB-INF/bar.jsp. No need for complex checks on numbers. Just use the filename as parameter.

Note that the include JSP is been placed in /WEB-INF folder to prevent endusers from being able to open it directly by either purposefully or accidently calling its URL in browser address bar.

You can put it in a JSTL <c:catch> to prevent an exception from being thrown if the file doesn’t exist.