Getting Program Output into a Window
You want to capture an input/output stream and display it in a text field.
Use an interconnected pair of piped streams and a
Thread to read from the input half, and write it
to the text area. You may also want to redirect
the stream; see Section 9.7.
PipedOutputStream provide two streams (see Chapter 9) that are connected together by
a buffer and are designed to provide communication between multiple
threads (see Section 24.1).
As you’ll see in Chapter 19, I am fairly
aggressive in the pursuit of SPAM perpetrators. I have a program
, derived from the mail sender in Section 19.3, that I use to test whether remote servers are
willing to accept mail from unknown third parties and forward it as
their own. This gives these bastard messages a parent, just as many
birds will glibly nest on a cuckoo’s egg that has been snuck
into their nest. This is the GUI for that program; both this and the
main program are online in the email directory.
In the constructor, I arrange for the main class to write to the
PipedOutputStream; the call to
TestOpenMailRelay.process( ) passing the
ps argument arranges this. That method will write its own output to the stream in addition to assigning standard output and standard error, so we should see anything it tries to print. To avoid long (possibly infinitely long!) delays, I start an additional thread to read from ...