Re: A stream/pipe that fills only on demand...

From:

Nigel Wade <nmw@ion.le.ac.uk>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 10 Nov 2014 09:24:31 +0000

Message-ID:

<ccbeifFtvl7U1@mid.individual.net>

On 07/11/14 09:34, Andreas Leitgeb wrote:

My needs are a bit different, though: I need a pipe-stream
that recognizes reader's request for bytes, and tells the
writer-end about the requested volume, and then the writer
will write just as much into the pipe as is needed by the
reader. The reader just uses the normal API that InputStream
offers, but I need these calls to identify themselves to the
pipe-writer, which would use a (yet unspecified) special API,
so the writer knows how much to put into the pipe-stream.

That's one scenario, but it's not the only one.
What you are essentially describing is a read request, write response.
The reader sends a request to the writer telling it what it wants and
the writer sends a response which the reader can read.

Background is, that the items that the writer will put into
the pipe-stream are "precious" and must not be wasted.
Kind of like reading back a stream of serialized data, where
each de-serializing object must not consume more than its own
bytes, but the Object needing its data is on a different host
than the byte stream. That's just an analogy - don't stress it.

When I need to do something similar I use either GenericServlet or RMI. Normally servlet for inter-host and RMI for
inter-process, but there's no reason why you can't use either approach for either solution. Both of them are suitable
for request/response operations. RMI has less overhead because it doesn't require a servlet engine, just the rmiregistry.