Chain the output of one process to the input of another process

Question

I need to pass data from one process to another through the blocking input/output streams. Is there anything ready to be used in JVM world?

How do I make the output of one process become the input of another process?

Answer 1

From a single thread you can use:

InputStream input = process.getInputStream();
OutputStream output = process.getOutputStream();

byte[] buffer = new byte[8192];
int amountRead;
while ((amountRead = input.read(buffer)) != -1) {
    output.write(buffer, 0, amountRead);
}

If you want to use two threads, you can use PipedInputStream and PipedOutputStream :

PipedOutputStream producer = new PipedOutputStream();
PipedInputStream consumer = new PipedInputStream(producer);

// This thread reads the input from one process, and publishes it to another thread
byte[] buffer = new byte[8192];
int amountRead;
while ((amountRead = input.read(buffer)) != -1) {
    producer.write(buffer, 0, amountRead);
}

// This thread consumes what has been published, and writes it to another process
byte[] buffer = new byte[8192];
int amountRead;
while ((amountRead = consumer.read(buffer)) != -1) {
    output.write(buffer, 0, amountRead);
}