是否可以在JSP中定义方法并从servlet调用它

Question

suppose the following JSP tag

<%! public void test(){} %>

Is it possible to define a method (eg the above test() method) in a jsp page and then call it from a servlet class?
if the answer is yes, then how it can be done? if the answer is no, then why?

(I know that before running a JSP page the web server complies it into a servlet class)

Answer 1

What normally happens is you map the request to the servlet, and the servlet forwards to the JSP.

String nextJSP = "/searchResults.jsp";
RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(nextJSP);
dispatcher.forward(request,response);

You can't invoke a method on your JSP, because the servlet does not have access to the compiled JSP directly, it only has access to the dispatcher.

But what usually is done, is setting of request attributes in the servlet and then the JSP can pick these up.

So in the top of the JSP, you could do something like

<% if(request.getAttribute("doTest")) then test(); %>