Warkior Warkior - 5 months ago 50
Java Question

How to create a Java non-blocking InputStream from a HttpsURLConnection?

Basically, I have a URL that streams xml updates from a chat room when new messages are posted. I'd like to turn that URL into an InputStream and continue reading from it as long as the connection is maintained and as long as I haven't sent a Thread.interrupt(). The problem I'm experiencing is that BufferedReader.ready() doesn't seem to become true when there is content to be read from the stream.

I'm using the following code:

BufferedReader buf = new BufferedReader(new InputStreamReader(ins));


String str = "";
while(Thread.interrupted() != true)
{
connected = true;
debug("Listening...");

if(buf.ready())
{
debug("Something to be read.");
if ((str = buf.readLine()) != null) {
// str is one line of text; readLine() strips the newline character(s)
urlContents += String.format("%s%n", str);
urlContents = filter(urlContents);
}
}

// Give the system a chance to buffer or interrupt.
try{Thread.sleep(1000);} catch(Exception ee) {debug("Caught thread exception.");}
}


When I run the code, and post something to the chat room, buf.ready() never becomes true, resulting in the lines never being read. However, if I skip the "buf.ready()" part and just read lines directly, it blocks further action until lines are read.

How do I either a) get buf.ready() to return true, or b) do this in such a way as to prevent blocking?

Thanks in advance,
James

EJP EJP
Answer

Reader.ready() returns true when data can be read without blocking. Period. InputStreams and Readers are blocking. Period. Everything here is working as designed. If you want more concurrency with these APIs you will have to use multiple threads. Or Socket.setSoTimeout() and its near relation in HttpURLConnection.

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