you write are placed inside a single method of this class.
You can also add variable and method declarations to this class.
You can then use these variables and methods from your scriptlets and expressions.
To add a declaration, you must use the <%! and %>
sequences to enclose your declarations, as shown below.
<%@ page import="java.util.*" %>
<HTML>
<BODY>
<%!
Date theDate = new Date();
Date getDate()
{
System.out.println( "In getDate() method" );
return theDate;
}
%>
Hello! The time is now <%= getDate() %>
</BODY>
</HTML>
The example has been created a little contrived, to show variable and method
declarations.
Here we are declaring a Date variable theDate, and the method
getDate.
Both of these are available now in our scriptlets and expressions.
But this example no longer works! The date will be the same, no
matter how often you reload the page. This is because these are declarations,
and will only be evaluated once when the page is loaded! (Just as
if you were creating a class and had variable initialization declared in
it.)
Exercise: Modify the above example to add another function
computeDate
which re-initializes theDate. Add a scriptlet that calls
computeDate
each time.
Note: Now that you know how to do this -- it is in general not a good idea to use variables as shown
here. The JSP usually will run as multiple threads of
one single instance. Different threads would interfere with
variable access, because it will be the same variable for all of
them. If you do have to use variables in JSP, you should use
synchronized access, but that hurts the performance.
In general, any data you need should go either in the session
object or the request object (these are introduced a little
later) if passing data between
different JSP pages. Variables you declare inside scriptlets
are fine, e.g. <% int i = 45; %> because these are declared
inside the local scope and are not shared.
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