Servlets: Java Pressed into Service - Java Application Development on Linux - page 418

Table 18.1 BudgetPro servlet actions

func parameter Other params Action Next screen

name , dollars Create a top-level account, save in

the session.

begin main

none none mkacct subacct

none Get account from session.

cancel main

name , dollars Get account from session; create

subaccount.

create main

Get account from session, look up
subaccount by name , save as current
in session.

cd name main

none Get account from session, get

parent from account, save as current
in session.

back main

The parsing of the parameters is very straightforward. The request param-
eter, part of the signature of the doGet() and doPost() methods, can be used
to retrieve the parameters we need:

String act = request.getParameter("func");
String name = request.getParameter("name");
String dollars = request.getParameter("dollars");

Notice that we always ask for all three parameters, even though we will
often use only one ( act ). Once we have the requested function in act , it's just
a matter of if-then-else-ing our way through the possible values and taking
the appropriate actions. We store, or retrieve, the current account in the
session manager, thereby providing continuity between browser requests
(Example 18.2).
The output is the page to send back to the browser. We create
that page as an object, either an AccountView or a SubPage . The
HttpServletResponse provides us with an output channel on which to write.

java.io.PrintWriter out = response.getWriter();
if (nextPage != null) {
response.setContentType("text/html");
out.println(nextPage.toString());
}