Java Reference
In-Depth Information
L
ISTING
6.6
Continued
6
response_order.getStatus());
}
else {
System.err.println(“readObject failed.”);
}
}
catch (MalformedURLException mue) {
System.err.println(mue.getMessage());
}
catch (Exception e) {
System.err.println(e.getMessage());
}
}
}
The three areas of the applet you must focus on are the
jGetStatusButton_actionPerformed()
,
writeOrder()
, and
readOrder()
methods. These
methods make up the functional areas of the applet.
The
jGetStatusButton_actionPerformed()
method is where the transaction is invoked. It
creates an
Order
object, setting the
order
attribute to the value typed into the
jOrderTextField
swing component. It then opens a URL connection pointing to your
OrderStatusServlet
,
http://localhost/djs/servlet/OrderStatusServlet
. The connec-
tion and the order are then passed to the
writeOrder()
method.
The
writeOrder()
method first sets the appropriate properties of the
Connection
object. It
then creates an
ObjectOutputStream
using the
OutputStream
of the connection. When the
ObjectOutputStream
is successfully created, the
Order
object is written to it.
When the
writeOrder()
method returns, the
readOrder()
method is called. It takes the
URLConnection
object passed to it and creates an
ObjectInputStream
. It then calls the
ObjectInputStream
's
readObject()
method, which block reads until a response object is
received. This new
Order
object is then returned to the calling method.
The
jGetStatusButton_actionPerformed()
method then takes the
Order
object that was
returned to it and calls the
getStatus()
method, passing the returned status to the
jStatusResultTextArea
's
setText()
method.
Compile these classes, making sure that the
swingall.jar
file, which contains all the swing
components, is in your
CLASSPATH
. The HTML used to load this applet is shown in Listing 6.7.
