Newbie EL help needed

Question

I've done quite a bit of JSP work and am now trying to grok JSP 2.0 with Tomcat 5.0.28.
Why does example A work yet B doesn't?
A) ${33}
B)
<% int x = 33; %>
${x}

Answer 1

In EL, there are only four scopes, represented by four scope objects:
page scope -- the pageContext object
request scope -- the request object
session scope -- the session object
application -- the servletContext object
EL will find a value stored in any one of these four scopes. However, when you are using scriptlets,
<% x = 33 %>
You are inserting that java code directly into the JSP's service method (remember, JSPs are translated into Servlets, and then compiled into .class files before they are displayed...). The value is local to the service method and not stored in any of the four scope objects.
In order to access a value from a scriptlet, you could do:
<%
  Integer x = 33; //I don't think you can use int here, I think it needs to be an Object
  pageContext.setAttribute("x", x); //put the value of the variable x into the pageContext with a name of x
%>
  ${x} //Will give the first value named x when searching page, request, session, application scopes