dispatcher.forward（）和。之间有什么区别吗？ <jsp:forward> ？

Question

Are the following operations exactly identical :

request.setAttribute(name,"visited");
requestDispatcher.forward(request,response)

and

<jsp:forward page="page.jsp">
  <jsp:param name="status" value="visited"/>
</jsp:forward>

Answer 1

both are same, only difference is separate tag handler class is written for <jsp:forward> .

See tutorial for tag handler.

Answer 2

There is no functional difference. Both <jsp:forward> and RequestDispatcher.forward() are same in fact <jsp:forward> internally used the RequestDispatcher.forward() to forward the request. is action tag and there is tag handler class . Always remember JSP also going convert to a servlet, by the web container.

Answer 3

If only consider the forward action, there is no functional diffrerence. But they seems not fully the same. I test the following code.

<%
System.out.println("source 1");
RequestDispatcher disp = request.getRequestDispatcher("1_f1.jsp");
disp.forward(request, response);
System.out.println("source 2");
%>

and

<%
System.out.println("source 1");
%>
<jsp:forward page="1_f1.jsp"/>
<%
System.out.println("source 2");
%>

When using disp.forward() , console will output "source 2". But when using <jsp:forward/> , "source 2" will not be output.

The is converted to the following statements.

pageContext = _jspxFactory.getPageContext(this, request, response,
    null, true, 8192, true);
_jspx_page_context = pageContext;
if (true) {
    _jspx_page_context.forward("1_f1.jsp");
    return;
}

Here is a return; statement. So, the code after <jsp:forward/> will not run.