Head First Servlets and JSP, 2nd Edition

Expressions become the argument to an out.print()

In other words, the Container takes everything you type between the <%= and %> and puts it in as the argument to a statement that prints to the implicit response PrintWriter out.

When the Container sees this:

<%= Counter.getCount() %>

It turns it into this:

out.print(Counter.getCount());

If you did put a semicolon in your expression:

<%= Counter.getCount(); %>

That would be bad. It would mean this:

Note

NEVER end an expression with a semicolon!

<%= neverPutASemicolonInHere %>

<%= becauseThisIsAnArgumentToPrint() %>

There are no Dumb Questions

Q:	Q: Well, if you’re supposed to use expressions INSTEAD of putting out.println() into a scriptlet, then why is the implicit “out” there?
A:	A: You probably won’t use the implicit out variable from within your JSP page, but you might pass it to something else... some other object that’s part of your app that does not have direct access to the output stream for the response.
Q:	Q: In an expression, what happens if the method doesn’t return anything?
A:	A: You’ll get an error!! You cannot, MUST NOT use a method with a void return type as an expression. The Container is smart enough to figure out that there won’t be anything ...